1 @c -*- coding: utf-8; mode: texinfo; -*-
4 Translation of GIT committish: FILL-IN-HEAD-COMMITTISH
6 When revising a translation, copy the HEAD committish of the
7 version that you are working on. For details, see the Contributors'
8 Guide, node Updating translation committishes..
13 @node Changing defaults
14 @chapter Changing defaults
16 The purpose of LilyPond's design is to provide the finest quality
17 output by default. Nevertheless, it may happen that you need to
18 change this default layout. The layout is controlled through a large
19 number of @q{knobs and switches} collectively called @q{properties}.
20 A tutorial introduction to accessing and modifying these properties
21 can be found in the Learning Manual, see @rlearning{Tweaking output}.
22 This should be read first. This chapter covers similar ground, but
23 in a style more appropriate to a reference manual.
25 @cindex Internals Reference
27 The definitive description of the controls available for tuning can
28 be found in a separate document: @rinternalsnamed{Top,the Internals
29 Reference}. That manual lists all the variables, functions and
30 options available in LilyPond. It is written as a HTML document,
32 @c leave the @uref as one long line.
33 @uref{http://@/lilypond@/.org/@/doc/@/stable/@/Documentation/@/internals/,on@/-line},
34 and is also included with the LilyPond documentation package.
36 Internally, LilyPond uses Scheme (a LISP dialect) to provide
37 infrastructure. Overriding layout decisions in effect accesses the
38 program internals, which requires Scheme input. Scheme elements are
39 introduced in a @file{.ly} file with the hash
40 mark@tie{}@code{#}.@footnote{@rextend{Scheme tutorial}, contains a
41 short tutorial on entering numbers, lists, strings, and symbols in
46 * Interpretation contexts::
47 * Explaining the Internals Reference::
48 * Modifying properties::
49 * Useful concepts and properties::
51 * Using music functions::
55 @node Interpretation contexts
56 @section Interpretation contexts
58 This section describes what contexts are, and how to modify them.
61 * Contexts explained::
62 * Creating and referencing contexts::
63 * Keeping contexts alive::
64 * Modifying context plug-ins::
65 * Changing context default settings::
66 * Defining new contexts::
67 * Context layout order::
72 @rlearning{Contexts and engravers}.
75 @file{ly/engraver-init.ly},
76 @file{ly/performer-init.ly}.
79 @rlsr{Contexts and engravers}.
82 @rinternals{Contexts},
83 @rinternals{Engravers and Performers}.
86 @node Contexts explained
87 @subsection Contexts explained
90 @c TODO Rethink and rewrite
92 >> > > - list of contexts: my *danger unmaintainable*
93 >> > > alarm just went off. I'm
94 I knew it would... And leaving out some of them is perfectly fine
95 with me. I do think that a list like this, with the main contexts and a
96 brief description of what they do (perhaps also with a note about what
97 default behavior is associated with each of them, but this may be
98 unmanageable), should be there, and then we could simply list the
99 remaining ones without further explanation and with links to the IR.
102 @c TODO Improve layout, order and consistency of wording -td
104 @c TODO Add introduction which explains contexts in generality -td
106 @c TODO Describe propagation of property values -td
108 Contexts are arranged hierarchically:
111 * Output definitions - blueprints for contexts::
112 * Score - the master of all contexts::
113 * Top-level contexts - staff containers::
114 * Intermediate-level contexts - staves::
115 * Bottom-level contexts - voices::
118 @node Output definitions - blueprints for contexts
119 @unnumberedsubsubsec Output definitions - blueprints for contexts
121 This section explains the relevance of output definitions when
122 working with contexts. Examples for actual output definitions are
123 given later (see @ref{Changing all contexts of the same type}).
125 @cindex output definitions
127 While music written in a file may refer to context types and
128 names, contexts are created only when the music is actually being
129 interpreted. LilyPond interprets music under control of an
130 @q{output definition} and may do so for several different output
131 definitions, resulting in different output. The output definition
132 relevant for printing music is specified using @code{\layout}.
135 A much simpler output definition used for producing Midi output is
136 specified using @code{\midi}. Several other output definitions
137 are used by LilyPond internally, like when using the part combiner
138 (@ref{Automatic part combining}) or creating music quotes
139 (@ref{Quoting other voices}).
141 Output definitions define the relation between contexts as well as
142 their respective default settings. While most changes will
143 usually be made inside of a @code{\layout} block, Midi-related
144 settings will only have an effect when made within a @code{\midi}
147 @funindex autoBeaming
148 Some settings affect several outputs: for example, if
149 @code{autoBeaming} is turned off in some context, beams count as
150 melismata for the purpose of matching music to lyrics as described
151 in @ref{Automatic syllable durations}. This matching is done both
152 for printed output as well as for Midi. If changes made to
153 @code{autoBeaming} within a context definition of a @code{\layout}
154 block are not repeated in the corresponding @code{\midi} block,
155 lyrics and music will get out of sync in Midi.
159 @file{ly/engraver-init.ly}.
160 @file{ly/performer-init.ly}.
162 @node Score - the master of all contexts
163 @unnumberedsubsubsec Score - the master of all contexts
165 This is the top level notation context. No other context can
166 contain a Score context. By default the Score context handles
167 the administration of time signatures and makes sure that items
168 such as clefs, time signatures, and key-signatures are aligned
171 A Score context is instantiated implicitly when a
172 @code{\score @{@dots{}@}} block is processed.
174 @node Top-level contexts - staff containers
175 @unnumberedsubsubsec Top-level contexts - staff containers
177 @strong{@emph{StaffGroup}}
179 Groups staves while adding a bracket on the left side, grouping
180 the staves together. The bar lines of the contained staves are
181 connected vertically. @code{StaffGroup} only consists of a collection
182 of staves, with a bracket in front and spanning bar lines.
184 @strong{@emph{ChoirStaff}}
186 Identical to @code{StaffGroup} except that the bar lines of the
187 contained staves are not connected vertically.
189 @strong{@emph{GrandStaff}}
191 A group of staves, with a brace on the left side, grouping the
192 staves together. The bar lines of the contained staves are
193 connected vertically.
195 @strong{@emph{PianoStaff}}
197 Just like @code{GrandStaff}, but with support for instrument names
198 to the left of each system.
200 @node Intermediate-level contexts - staves
201 @unnumberedsubsubsec Intermediate-level contexts - staves
203 @strong{@emph{Staff}}
205 Handles clefs, bar lines, keys, accidentals. It can contain
206 @code{Voice} contexts.
208 @strong{@emph{RhythmicStaff}}
210 Like @code{Staff} but for printing rhythms. Pitches are ignored
211 when engraving; the notes are printed on one line. The MIDI
212 rendition retains pitches unchanged.
214 @strong{@emph{TabStaff}}
216 Context for generating tablature. By default lays the music
217 expression out as a guitar tablature, printed on six lines.
219 @strong{@emph{DrumStaff}}
221 Handles typesetting for percussion. Can contain @code{DrumVoice}.
223 @strong{@emph{VaticanaStaff}}
225 Same as @code{Staff}, except that it is designed for typesetting
226 a piece in gregorian style.
228 @strong{@emph{MensuralStaff}}
230 Same as @code{Staff}, except that it is designed for typesetting
231 a piece in mensural style.
233 @node Bottom-level contexts - voices
234 @unnumberedsubsubsec Bottom-level contexts - voices
236 Voice-level contexts initialise certain properties and start
237 appropriate engravers. A bottom-level context is one without
238 @code{defaultchild}. While it is possible to let it
239 accept/@/contain subcontexts, they can only be created and entered
242 @strong{@emph{Voice}}
244 Corresponds to a voice on a staff. This context handles the
245 conversion of dynamic signs, stems, beams, super- and sub-scripts,
246 slurs, ties, and rests. You have to instantiate this explicitly
247 if you require multiple voices on the same staff.
249 @strong{@emph{VaticanaVoice}}
251 Same as @code{Voice}, except that it is designed for typesetting
252 a piece in gregorian style.
254 @strong{@emph{MensuralVoice}}
256 Same as @code{Voice}, with modifications for typesetting a piece in
259 @strong{@emph{Lyrics}}
261 Corresponds to a voice with lyrics. Handles the printing of a
262 single line of lyrics.
264 @strong{@emph{DrumVoice}}
266 The voice context used in a percussion staff.
268 @strong{@emph{FiguredBass}}
270 The context in which @code{BassFigure} objects are created from
271 input entered in @code{\figuremode} mode.
273 @strong{@emph{TabVoice}}
275 The voice context used within a @code{TabStaff} context. Usually
276 left to be created implicitly.
278 @strong{@emph{CueVoice}}
280 A voice context used to render notes of a reduced size, intended
281 primarily for adding cue notes to a staff, see @ref{Formatting
282 cue notes}. Usually left to be created implicitly.
284 @strong{@emph{ChordNames}}
286 Typesets chord names.
291 Then the following, which I don't know what to do with:
293 * GregorianTranscriptionVoice
294 * GregorianTranscriptionStaff
297 Engraves fretboards from chords. Not easy... Not
299 There is now some documentation on FretBoards in the NR, under
300 instrument-specific notation -- cds.
305 Hard coded entry point for LilyPond. Cannot be tuned.
307 Silently discards all musical information given to this
312 @node Creating and referencing contexts
313 @subsection Creating and referencing contexts
318 @cindex referencing contexts
319 @cindex Contexts, creating and referencing
321 LilyPond will create lower-level contexts automatically if a music
322 expression is encountered before a suitable context exists, but this
323 is usually successful only for simple scores or music fragments like
324 the ones in the documentation. For more complex scores it is
325 advisable to specify all contexts explicitly with either the
326 @code{\new} or @code{\context} command. The syntax of
327 these two commands is very similar:
330 [\new | \context] @var{Context} [ = @var{name}] [@var{music-expression}]
334 where either @code{\new} or @code{\context} may be specified.
335 @var{Context} is the type of context which is to be created,
336 @var{name} is an optional name to be given to the particular context
337 being created and @var{music-expression} is a single music expression
338 that is to be interpreted by the engravers and performers in this
341 The @code{\new} prefix without a name is commonly used to create
342 scores with many staves:
344 @lilypond[quote,verbatim]
346 \new Staff \relative {
347 % leave the Voice context to be created implicitly
350 \new Staff \relative {
357 and to place several voices into one staff:
359 @lilypond[quote,verbatim]
361 \new Voice \relative {
365 \new Voice \relative {
373 @code{\new} should always be used to specify unnamed contexts.
375 The difference between @code{\new} and @code{\context} is in the
380 @code{\new} with or without a name will always create a fresh,
381 distinct, context, even if one with the same name already exists:
383 @lilypond[quote,verbatim]
385 \new Voice = "A" \relative {
389 \new Voice = "A" \relative {
397 @code{\context} with a name specified will create a distinct context
398 only if a context of the same type with the same name in the same
399 context hierarchy does not already exist. Otherwise it will be taken
400 as a reference to that previously created context, and its music
401 expression will be passed to that context for interpretation.
403 One application of named contexts is in separating the score layout
404 from the musical content. Either of these two forms is valid:
406 @lilypond[quote,verbatim]
420 \context Voice = "one" {
425 \context Voice = "two" {
434 @lilypond[quote,verbatim]
439 \context Voice = "one" {
442 \context Voice = "two" {
448 \context Voice = "one" {
453 \context Voice = "two" {
463 Alternatively, variables may be employed to similar effect. See
464 @rlearning{Organizing pieces with variables}.
467 @code{\context} with no name will match the first of any previously
468 created contexts of the same type in the same context heirarchy,
469 even one that has been given a name, and its music expression will be
470 passed to that context for interpretation. This form is rarely
471 useful. However, @code{\context} with no name and no music expression
472 is used to set the context in which a Scheme procedure specified with
473 @code{\applyContext} is executed:
476 \new Staff \relative @{
479 \applyContext #(lambda (ctx)
481 (display (ly:context-current-moment ctx)))
488 A context must be named if it is to be referenced later, for example
489 when lyrics are associated with music:
492 \new Voice = "tenor" @var{music}
494 \new Lyrics \lyricsto "tenor" @var{lyrics}
498 For details of associating lyrics with music see
499 @ref{Automatic syllable durations}.
501 The properties of all contexts of a particular type can be modified
502 in a @code{\layout} block (with a different syntax), see
503 @ref{Changing all contexts of the same type}. This construct also
504 provides a means of keeping layout instructions separate from the
505 musical content. If a single context is to be modified, a @code{\with}
506 block must be used, see @ref{Changing just one specific context}.
510 @rlearning{Organizing pieces with variables}.
513 @ref{Changing just one specific context},
514 @ref{Automatic syllable durations}.
517 @node Keeping contexts alive
518 @subsection Keeping contexts alive
520 @cindex contexts, keeping alive
521 @cindex contexts, lifetime
523 Contexts are usually terminated at the first musical moment in
524 which they have nothing to do. So @code{Voice} contexts die as
525 soon as they contain no events; @code{Staff} contexts die as soon
526 as all the @code{Voice} contexts within them contain no events; etc.
527 This can cause difficulties if earlier contexts which have died
528 have to be referenced, for example, when changing staves with
529 @code{\change} commands, associating lyrics with a voice with
530 @code{\lyricsto} commands, or when adding further musical events to
533 There is an exception to this general rule: inside of an
534 @code{@{@dots{}@}} construct (sequential music), the construct's
535 notion of the ``current context'' will descend whenever an element
536 of the sequence ends in a subcontext of the previous current
537 context. This avoids spurious creation of implicit contexts in a
538 number of situations but means that the first context descended
539 into will be kept alive until the end of the expression.
541 In contrast, the contexts of a @code{<<@dots{}>>} construct's
542 (simultaneous music) expression are not carried forth, so
543 enclosing a context creating command in an extra pair of
544 @code{<<@dots{}>>} will keep the context from persisting through
545 all of the enclosing @code{@{@dots{}@}} sequence.
547 Any context can be kept alive by ensuring it has something to do at
548 every musical moment. @code{Staff} contexts are kept alive by
549 ensuring one of their voices is kept alive. One way of doing this
550 is to add spacer rests to a voice in parallel with the real music.
551 These need to be added to every @code{Voice} context which needs to
552 be kept alive. If several voices are to be used sporadically it is
553 safest to keep them all alive rather than attempting to rely on the
554 exceptions mentioned above.
556 In the following example, both voice A and voice B are kept alive
557 in this way for the duration of the piece:
559 @lilypond[quote,verbatim]
560 musicA = \relative { d''4 d d d }
561 musicB = \relative { g'4 g g g }
564 \new Voice = "A" { s1*5 } % Keep Voice "A" alive for 5 bars
565 \new Voice = "B" { s1*5 } % Keep Voice "B" alive for 5 bars
570 \context Voice = "A" {
574 \context Voice = "B" {
578 \context Voice = "A" { \musicA }
579 \context Voice = "B" { \musicB }
580 \context Voice = "A" { \musicA }
591 @cindex lyrics, aligning with sporadic melody
593 The following example shows how a sporadic melody line with lyrics
594 might be written using this approach. In a real situation the
595 melody and accompaniment would consist of several different
598 @lilypond[quote,verbatim]
599 melody = \relative { a'4 a a a }
600 accompaniment = \relative { d'4 d d d }
601 words = \lyricmode { These words fol -- low the mel -- o -- dy }
604 \new Staff = "music" {
606 \new Voice = "melody" {
608 s1*4 % Keep Voice "melody" alive for 4 bars
611 \new Voice = "accompaniment" {
616 \context Voice = "melody" { \melody }
617 \context Voice = "accompaniment" { \accompaniment }
619 \context Voice = "accompaniment" { \accompaniment }
621 \context Voice = "melody" { \melody }
622 \context Voice = "accompaniment" { \accompaniment }
627 \new Lyrics \with { alignAboveContext = #"music" }
628 \lyricsto "melody" { \words }
633 An alternative way, which may be better in many circumstances, is
634 to keep the melody line alive by simply including spacer notes to
635 line it up correctly with the accompaniment:
637 @lilypond[quote,verbatim]
644 accompaniment = \relative {
650 words = \lyricmode { These words fol -- low the mel -- o -- dy }
654 \new Staff = "music" {
656 \new Voice = "melody" {
660 \new Voice = "accompaniment" {
666 \new Lyrics \with { alignAboveContext = #"music" }
667 \lyricsto "melody" { \words }
673 @node Modifying context plug-ins
674 @subsection Modifying context plug-ins
676 @c TODO Should this be Modifying engravers or Modifying contexts?
678 Notation contexts (like @code{Score} and @code{Staff}) not only store
679 properties, they also contain plug-ins called @q{engravers} that create
680 notation elements. For example, the @code{Voice} context contains a
681 @code{Note_heads_engraver} and the @code{Staff} context contains a
684 For a full a description of each plug-in, see
686 @rinternals{Engravers and Performers}.
689 Internals Reference @expansion{} Translation @expansion{} Engravers.
691 Every context described in
693 @rinternals{Contexts}
696 Internals Reference @expansion{} Translation @expansion{} Context.
698 lists the engravers used for that context.
701 It can be useful to shuffle around these plug-ins. This is done by
702 starting a new context with @code{\new} or @code{\context}, and
708 \new @var{context} \with @{
716 @emph{@dots{}music@dots{}}
721 where the @dots{} should be the name of an engraver. Here is a simple
722 example which removes @code{Time_signature_engraver} and
723 @code{Clef_engraver} from a @code{Staff} context,
725 @lilypond[quote,verbatim]
727 \new Staff \relative {
731 \remove "Time_signature_engraver"
732 \remove "Clef_engraver"
739 In the second staff there are no time signature or clef symbols. This
740 is a rather crude method of making objects disappear since it will affect
741 the entire staff. This method also influences the spacing, which may or
742 may not be desirable. More sophisticated methods of blanking objects
743 are shown in @rlearning{Visibility and color of objects}.
745 The next example shows a practical application. Bar lines and time
746 signatures are normally synchronized across the score. This is done
747 by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
748 This plug-in keeps an administration of time signature, location
749 within the measure, etc. By moving these engraver from @code{Score} to
750 @code{Staff} context, we can have a score where each staff has its own
753 @cindex polymetric scores
754 @cindex time signature, multiple
756 @lilypond[quote,verbatim]
760 \consists "Timing_translator"
761 \consists "Default_bar_line_engraver"
768 \consists "Timing_translator"
769 \consists "Default_bar_line_engraver"
779 \remove "Timing_translator"
780 \remove "Default_bar_line_engraver"
788 The order in which the engravers are specified is the order in
789 which they are called to carry out their processing. Usually the
790 order in which the engravers are specified does not matter, but in
791 a few special cases the order is important, for example where one
792 engraver writes a property and another reads it, or where one
793 engraver creates a grob and another must process it.
795 The following orderings are important:
799 the @code{Bar_engraver} must normally be first,
802 the @code{New_fingering_engraver} must come before the
803 @code{Script_column_engraver},
806 the @code{Timing_translator} must come before the
807 @code{Bar_number_engraver}.
813 @file{ly/engraver-init.ly}.
816 @node Changing context default settings
817 @subsection Changing context default settings
819 @cindex default context properties, changing
820 @cindex context properties, changing defaults
822 Context and grob properties can be changed with @code{\set}
823 and @code{\override} commands, as described in
824 @ref{Modifying properties}. These commands create music events,
825 making the changes take effect at the point in time the music
828 In contrast, this section explains how to change the @emph{default}
829 values of context and grob properties at the time the context is
830 created. There are two ways of doing this. One modifies the default
831 values in all contexts of a particular type, the other modifies the
832 default values in just one particular instance of a context.
835 * Changing all contexts of the same type::
836 * Changing just one specific context::
837 * Order of precedence::
840 @node Changing all contexts of the same type
841 @unnumberedsubsubsec Changing all contexts of the same type
843 @cindex \context in \layout block
847 The default context settings which are to be used for typesetting in
848 @code{Score}, @code{Staff}, @code{Voice} and other contexts may be
849 specified in a @code{\context} block within any @code{\layout}
852 Settings for Midi output as opposed to typesetting will have to be
853 separately specified in @code{\midi} blocks (see @ref{Output
854 definitions - blueprints for contexts}).
856 The @code{\layout} block should be placed within the @code{\score}
857 block to which it is to apply, after the music.
863 [context settings for all Voice contexts]
867 [context settings for all Staff contexts]
872 The following types of settings may be specified:
876 An @code{\override} command, but with the context name omitted
878 @lilypond[quote,verbatim]
881 a'4^"Thicker stems" a a a
887 \override Stem.thickness = #4.0
894 Directly setting a context property
896 @lilypond[quote,verbatim]
899 a'4^"Smaller font" a a a
912 A predefined command such as @code{\dynamicUp} or a music
913 expression like @code{\accidentalStyle dodecaphonic}
915 @lilypond[quote,verbatim]
918 a'4^"Dynamics above" a a a
928 \accidentalStyle dodecaphonic
935 A user-defined variable containing a @code{\with} block; for details
936 of the @code{\with} block see
937 @ref{Changing just one specific context}.
939 @lilypond[quote,verbatim]
940 StaffDefaults = \with {
947 a'4^"Smaller font" a a a
962 Property-setting commands can be placed in a @code{\layout} block
963 without being enclosed in a @code{\context} block. Such settings
964 are equivalent to including the same property-setting commands at
965 the start of every context of the type specified. If no context
966 is specified @emph{every} bottom-level context is affected, see
967 @ref{Bottom-level contexts - voices}. The syntax of a
968 property-setting command in a @code{\layout} block is the same as
969 the same command written in the music stream.
971 @lilypond[quote,verbatim]
975 a'4^"Smaller font" a a a
980 \accidentalStyle dodecaphonic
982 \override Voice.Stem.thickness = #4.0
988 @node Changing just one specific context
989 @unnumberedsubsubsec Changing just one specific context
994 The context properties of just one specific context instance can be
995 changed in a @code{\with} block. All other context instances of the
996 same type retain the default settings built into LilyPond and modified
997 by any @code{\layout} block within scope. The @code{\with} block
998 must be placed immediately after the @code{\new} @var{context-type}
1002 \new Staff \with @{ [context settings for this context instance only] @}
1008 Since such a @q{context modification} is specified inside of
1009 music, it will affect @emph{all} outputs (typesetting @emph{and}
1010 Midi) as opposed to changes within an output definition.
1012 The following types of settings may be specified:
1016 An @code{\override} command, but with the context name omitted
1018 @lilypond[quote,verbatim]
1021 \new Voice \with { \override Stem.thickness = #4.0 }
1024 a'4^"Thick stems" a a a
1033 Directly setting a context property
1035 @lilypond[quote,verbatim]
1040 a'4^"Default font" a a a
1044 \new Staff \with { fontSize = #-4 }
1047 a'4^"Smaller font" a a a
1056 A predefined command such as @code{\dynamicUp}
1058 @lilypond[quote,verbatim]
1064 a'4^"Dynamics below" a a a
1069 \new Staff \with { \accidentalStyle dodecaphonic }
1071 \new Voice \with { \dynamicUp }
1074 a'4^"Dynamics above" a a a
1085 @node Order of precedence
1086 @unnumberedsubsubsec Order of precedence
1088 The value of a property which applies at a particular time is
1089 determined as follows:
1093 if an @code{\override} or @code{\set} command in the input stream is
1094 in effect that value is used,
1097 otherwise the default value taken from a @code{\with} statement
1098 on the context initiation statement is used,
1101 otherwise the default value taken from the most recent appropriate
1102 @code{\context} block in the @code{\layout} or @code{\midi} blocks
1106 otherwise the LilyPond built-in default is used.
1111 @rlearning{Modifying context properties}.
1114 @ref{Contexts explained},
1115 @ref{Bottom-level contexts - voices},
1116 @ref{The set command},
1117 @ref{The override command},
1118 @ref{The layout block,,The @code{@bs{}layout} block}.
1121 @node Defining new contexts
1122 @subsection Defining new contexts
1124 @cindex contexts, defining new
1125 @cindex engravers, including in contexts
1140 Specific contexts, like @code{Staff} and @code{Voice}, are made from
1141 simple building blocks. It is possible to create new types of
1142 contexts with different combinations of engraver plug-ins.
1144 The next example shows how to build a different type of
1145 @code{Voice} context from scratch. It will be similar to
1146 @code{Voice}, but only prints centered slash note heads. It can be used
1147 to indicate improvisation in jazz pieces,
1149 @lilypond[quote,ragged-right]
1150 \layout { \context {
1152 \type "Engraver_group"
1153 \consists "Note_heads_engraver"
1154 \consists "Rhythmic_column_engraver"
1155 \consists "Text_engraver"
1156 \consists "Pitch_squash_engraver"
1157 squashedPosition = #0
1158 \override NoteHead.style = #'slash
1163 \accepts "ImproVoice"
1167 a'4 d8 bes8 \new ImproVoice { c4^"ad lib" c
1168 c4 c^"undress" c_"while playing :)" c }
1174 These settings are defined within a @code{\context} block inside a
1175 @code{\layout} block,
1185 In the following discussion, the example input shown should go in place
1186 of the @dots{} in the previous fragment.
1188 First it is necessary to define a name for the new context:
1194 Since it is similar to the @code{Voice} context, we want commands that
1195 work in (existing) @code{Voice} contexts to continue working. This is
1196 achieved by giving the new context an alias of @code{Voice},
1202 The context will print notes and instructive texts, so we need to add
1203 the engravers which provide this functionality, plus the engraver which
1204 groups notes, stems and rests which occur at the same musical moment
1208 \consists "Note_heads_engraver"
1209 \consists "Text_engraver"
1210 \consists "Rhythmic_column_engraver"
1213 The note heads should all be placed on the center line,
1216 \consists "Pitch_squash_engraver"
1217 squashedPosition = #0
1220 The @code{Pitch_squash_engraver} modifies note heads (created
1221 by the @code{Note_heads_engraver}) and sets their vertical
1222 position to the value of @code{squashedPosition}, in this
1223 case@tie{}@code{0}, the center line.
1225 The notes look like a slash, and have no stem,
1228 \override NoteHead.style = #'slash
1232 All these plug-ins have to communicate under the control of the
1233 context. The mechanisms with which contexts communicate are
1234 established by declaring the context @code{\type}. Within a
1235 @code{\layout} block, most contexts will be of type
1236 @code{Engraver_group}. Some special contexts and contexts in
1237 @code{\midi} blocks use other context types. Copying and
1238 modifying an existing context definition will also fill in the
1239 type. Since this example creates a definition from scratch, it
1240 needs to be specified explicitly.
1243 \type "Engraver_group"
1246 Put together, we get
1251 \type "Engraver_group"
1252 \consists "Note_heads_engraver"
1253 \consists "Text_engraver"
1254 \consists "Rhythmic_column_engraver"
1255 \consists "Pitch_squash_engraver"
1256 squashedPosition = #0
1257 \override NoteHead.style = #'slash
1264 Contexts form hierarchies. We want to place the @code{ImproVoice}
1265 context within the @code{Staff} context, just like normal @code{Voice}
1266 contexts. Therefore, we modify the @code{Staff} definition with the
1267 @code{\accepts} command,
1276 @funindex \inherit-acceptability
1277 Often when reusing an existing context definition, the resulting
1278 context can be used anywhere where the original context would have
1284 \inherit-acceptability @var{to} @var{from}
1289 will arrange to have contexts of type @var{to} accepted by all
1290 contexts also accepting @var{from}. For example, using
1295 \inherit-acceptability "ImproVoice" "Voice"
1300 will add an @code{\accepts} for @code{ImproVoice} to both
1301 @code{Staff} and @code{RhythmicStaff} definitions.
1304 The opposite of @code{\accepts} is @code{\denies},
1305 which is sometimes needed when reusing existing context definitions.
1307 Arranging the required pieces into a @code{\layout} block leaves
1316 \inherit-acceptability "ImproVoice" "Voice"
1320 Then the output at the start of this subsection can be entered as
1328 c c_"while playing :)"
1334 To complete this example, changes affecting the context hierarchy
1335 should be repeated in a @code{\midi} block so that Midi output
1336 depends on the same context relations.
1340 Internals Reference:
1341 @rinternals{Note_heads_engraver},
1342 @rinternals{Text_engraver},
1343 @rinternals{Rhythmic_column_engraver},
1344 @rinternals{Pitch_squash_engraver}.
1347 @node Context layout order
1348 @subsection Context layout order
1350 @cindex contexts, layout order
1354 Contexts are normally positioned in a system from top to bottom
1355 in the order in which they are encountered in the input file. When
1356 contexts are nested, the outer context will include inner nested
1357 contexts as specified in the input file, provided the inner contexts
1358 are included in the outer context's @qq{accepts} list. Nested
1359 contexts which are not included in the outer context's @qq{accepts}
1360 list will be repositioned below the outer context rather than nested
1363 The @qq{accepts} list of a context can be changed with the
1364 @code{\accepts} or @code{\denies} commands. @code{\accepts} adds a
1365 context to the @qq{accepts} list and @code{\denies} removes a context
1368 For example, a square-braced staff group is not usually found within a
1369 curved-braced staff with connecting staff bars, and a @code{GrandStaff}
1370 does not accept a @code{StaffGroup} inside it by default.
1372 @lilypond[verbatim,quote]
1379 \new Staff { \set Staff.instrumentName = bottom f'1 }
1384 However, by using the @code{\accepts} command, @code{StaffGroup} can be
1385 added to the @code{GrandStaff} context:
1387 @lilypond[verbatim,quote]
1394 \new Staff { \set Staff.instrumentName = bottom f'1 }
1399 \accepts "StaffGroup"
1405 @code{\denies} is mainly used when a new context is being based on
1406 another, but the required nesting differs. For example, the
1407 @code{VaticanaStaff} context is based on the @code{Staff} context, but
1408 with the @code{VaticanaVoice} context substituted for the @code{Voice}
1409 context in the @qq{accepts} list.
1411 @cindex contexts, implicit
1412 @cindex implicit contexts
1413 @funindex \defaultchild
1415 Note that a context will be silently created implicitly if a
1416 command is encountered when there is no suitable context available
1419 Within a context definition, the type of subcontext to be
1420 implicitly created is specified using @code{\defaultchild}. A
1421 number of music events require a @samp{Bottom} context: when such
1422 an event is encountered, subcontexts are created recursively until
1423 reaching a context with no @samp{defaultchild} setting.
1425 Implicit context creation can at times give rise to unexpected new
1426 staves or scores. Using @code{\new} to create contexts explicitly
1427 avoids those problems.
1429 @cindex alignAboveContext
1430 @cindex alignBelowContext
1431 @funindex alignAboveContext
1432 @funindex alignBelowContext
1434 Sometimes a context is required to exist for just a brief period, a
1435 good example being the staff context for an ossia. This is usually
1436 achieved by introducing the context definition at the appropriate
1437 place in parallel with corresponding section of the main music.
1438 By default, the temporary context will be placed below all the
1439 existing contexts. To reposition it above the context called
1440 @qq{main}, it should be defined like this:
1443 @code{\new Staff \with @{ alignAboveContext = #"main" @} }
1446 A similar situation arises when positioning a temporary lyrics
1447 context within a multi-staved layout such as a @code{ChoirStaff},
1448 for example, when adding a second verse to a repeated section.
1449 By default the temporary lyrics context will be placed beneath the
1450 lower staves. By defining the temporary lyrics context with
1451 @code{alignBelowContext} it can be positioned correctly beneath
1452 the (named) lyrics context containing the first verse.
1454 Examples showing this repositioning of temporary contexts can be
1455 found elsewhere --- see @rlearning{Nesting music expressions},
1456 @ref{Modifying single staves} and @ref{Techniques specific to lyrics}.
1460 @rlearning{Nesting music expressions}.
1463 @ref{Modifying single staves},
1464 @ref{Techniques specific to lyrics}.
1467 @rprogram{An extra staff appears}.
1470 @file{ly/engraver-init.ly}.
1473 @node Explaining the Internals Reference
1474 @section Explaining the Internals Reference
1477 * Navigating the program reference::
1478 * Layout interfaces::
1479 * Determining the grob property::
1480 * Naming conventions::
1483 @node Navigating the program reference
1484 @subsection Navigating the program reference
1486 @c TODO remove this (it's in the LM)
1487 @c Replace with more factual directions
1489 Suppose we want to move the fingering indication in the fragment
1492 @lilypond[quote,fragment,verbatim]
1496 If you visit the documentation on fingering instructions (in
1497 @ref{Fingering instructions}), you will notice:
1502 Internals Reference: @rinternals{Fingering}.
1507 @c outdated info; probably will delete.
1509 This fragment points to two parts of the program reference: a page
1510 on @code{FingeringEvent} and one on @code{Fingering}.
1512 The page on @code{FingeringEvent} describes the properties of the music
1513 expression for the input @w{@code{-2}}. The page contains many links
1514 forward. For example, it says
1517 Accepted by: @rinternals{Fingering_engraver},
1521 That link brings us to the documentation for the Engraver, the
1525 This engraver creates the following layout objects: @rinternals{Fingering}.
1528 In other words, once the @code{FingeringEvent}s are interpreted, the
1529 @code{Fingering_engraver} plug-in will process them.
1533 @c I can't figure out what this is supposed to mean. -gp
1535 The @code{Fingering_engraver} is also listed to create
1536 @rinternals{Fingering} objects,
1538 @c old info? it doesn't make any sense to me with our current docs.
1540 second bit of information listed under @b{See also} in the Notation
1545 The programmer's reference is available as an HTML document. It is
1546 highly recommended that you read it in HTML form, either online or
1547 by downloading the HTML documentation. This section will be much more
1548 difficult to understand if you are using the
1552 Follow the link to @rinternals{Fingering}. At the top of the
1556 Fingering objects are created by: @rinternals{Fingering_engraver} and
1557 @rinternals{New_fingering_engraver}.
1560 By following related links inside the program reference, we can follow the
1561 flow of information within the program:
1565 @item @rinternals{Fingering}:
1566 @rinternals{Fingering} objects are created by:
1567 @rinternals{Fingering_engraver}
1569 @item @rinternals{Fingering_engraver}:
1570 Music types accepted: @rinternals{fingering-event}
1572 @item @rinternals{fingering-event}:
1573 Music event type @code{fingering-event} is in Music expressions named
1574 @rinternals{FingeringEvent}
1577 This path goes against the flow of information in the program: it
1578 starts from the output, and ends at the input event. You could
1579 also start at an input event, and read with the flow of
1580 information, eventually ending up at the output object(s).
1582 The program reference can also be browsed like a normal document. It
1583 contains chapters on
1585 @rinternals{Music definitions},
1588 @code{Music definitions}
1590 on @rinternals{Translation}, and the @rinternals{Backend}. Every
1591 chapter lists all the definitions used and all properties that may be
1595 @node Layout interfaces
1596 @subsection Layout interfaces
1598 @cindex interface, layout
1599 @cindex layout interface
1602 The HTML page that we found in the previous section describes the
1603 layout object called @rinternals{Fingering}. Such an object is a
1604 symbol within the score. It has properties that store numbers (like
1605 thicknesses and directions), but also pointers to related objects. A
1606 layout object is also called a @emph{Grob}, which is short for Graphical
1607 Object. For more details about Grobs, see @rinternals{grob-interface}.
1609 The page for @code{Fingering} lists the definitions for the
1610 @code{Fingering} object. For example, the page says
1613 @code{padding} (dimension, in staff space):
1619 which means that the number will be kept at a distance of at least 0.5
1623 Each layout object may have several functions as a notational or
1624 typographical element. For example, the Fingering object
1625 has the following aspects
1629 Its size is independent of the horizontal spacing, unlike slurs or beams.
1632 It is a piece of text. Granted, it is usually a very short text.
1635 That piece of text is typeset with a font, unlike slurs or beams.
1638 Horizontally, the center of the symbol should be aligned to the
1639 center of the note head.
1642 Vertically, the symbol is placed next to the note and the staff.
1645 The vertical position is also coordinated with other superscript
1646 and subscript symbols.
1649 Each of these aspects is captured in so-called @emph{interface}s,
1650 which are listed on the @rinternals{Fingering} page at the bottom
1653 This object supports the following interfaces:
1654 @rinternals{item-interface},
1655 @rinternals{self-alignment-interface},
1656 @rinternals{side-position-interface}, @rinternals{text-interface},
1657 @rinternals{text-script-interface}, @rinternals{font-interface},
1658 @rinternals{finger-interface}, and @rinternals{grob-interface}.
1661 Clicking any of the links will take you to the page of the respective
1662 object interface. Each interface has a number of properties. Some of
1663 them are not user-serviceable (@q{Internal properties}), but others
1666 We have been talking of @emph{the} @code{Fingering} object, but actually it
1667 does not amount to much. The initialization file (see
1668 @rlearning{Other sources of information})
1669 @file{scm/define-grobs.scm} shows the soul of the @q{object},
1674 (avoid-slur . around)
1675 (slur-padding . 0.2)
1676 (staff-padding . 0.5)
1677 (self-alignment-X . 0)
1678 (self-alignment-Y . 0)
1679 (script-priority . 100)
1680 (stencil . ,ly:text-interface::print)
1681 (direction . ,ly:script-interface::calc-direction)
1682 (font-encoding . fetaText)
1683 (font-size . -5) ; don't overlap when next to heads.
1684 (meta . ((class . Item)
1685 (interfaces . (finger-interface
1687 text-script-interface
1689 side-position-interface
1690 self-alignment-interface
1691 item-interface))))))
1695 As you can see, the @code{Fingering} object is nothing more than a
1696 bunch of variable settings, and the webpage in the Internals Reference
1697 is directly generated from this definition.
1700 @node Determining the grob property
1701 @subsection Determining the grob property
1703 @c TODO remove this (it's in the LM)
1704 @c Replace with more factual directions
1706 Recall that we wanted to change the position of the @b{2} in
1708 @lilypond[quote,fragment,verbatim]
1712 Since the @b{2} is vertically positioned next to its note, we have to
1713 meddle with the interface associated with this positioning. This is
1714 done using @code{side-position-interface}. The page for this interface
1718 @code{side-position-interface}
1720 Position a victim object (this one) next to other objects (the
1721 support). The property @code{direction} signifies where to put the
1722 victim object relative to the support (left or right, up or down?)
1727 Below this description, the variable @code{padding} is described as
1732 (dimension, in staff space)
1734 Add this much extra space between objects that are next to each other.
1738 By increasing the value of @code{padding}, we can move the fingering
1739 away from the note head. The following command will insert @qq{three
1740 staff spaces} worth of distance between the note and a fingering mark:
1743 \once \override Voice.Fingering.padding = #3
1746 Inserting the padding before the fingering object is created results in
1749 @lilypond[quote,fragment,verbatim]
1750 \once \override Voice.Fingering.padding = #3
1754 In this case, the context for this tweak is @code{Voice}. See
1755 @rinternals{Fingering_engraver} plug-in, which says:
1758 Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
1762 @node Naming conventions
1763 @subsection Naming conventions
1765 Another thing that is needed, is an overview of the various naming
1769 @item scheme functions: lowercase-with-hyphens (also includes one-word
1772 @item LilyPond-specific scheme functions: ly:plus-scheme-style
1774 @item music events, music classes and music properties:
1777 @item Grob interfaces: scheme-style
1779 @item backend properties: scheme-style (but X and Y!)
1781 @item contexts (and MusicExpressions and grobs): Capitalized or
1784 @item context properties: lowercaseFollowedByCamelCase
1786 @item engravers: Capitalized_followed_by_lowercase_and_with_underscores
1789 Questions to be answered:
1792 @item Which of these are conventions and which are rules?
1794 @item Which are rules of the underlying language, and which are
1798 @node Modifying properties
1799 @section Modifying properties
1801 @c TODO change the menu and subsection node names to use
1802 @c backslash once the new macro to handle the refs
1803 @c is available. Need to find and change all refs at
1804 @c the same time. -td
1807 * Overview of modifying properties::
1809 * The override command::
1810 * The tweak command::
1811 * set versus override::
1812 * Modifying alists::
1816 @node Overview of modifying properties
1817 @subsection Overview of modifying properties
1819 Each context is responsible for creating certain types of graphical
1820 objects. The settings used for printing these objects are also stored by
1821 context. By changing these settings, the appearance of objects can be
1824 There are two different kinds of properties stored in contexts:
1825 context properties and grob properties. Context properties are
1826 properties that apply to the context as a whole and control
1827 how the context itself is displayed. In contrast, grob properties
1828 apply to specific grob types that will be displayed in the context.
1830 The @code{\set} and @code{\unset} commands are used to change values
1831 for context properties. The @code{\override} and @code{\revert}
1832 commands are used to change values for grob properties.
1835 The syntax for this is
1838 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1841 Here @var{name} is the name of a graphical object, like
1842 @code{Stem} or @code{NoteHead}, and @var{property} is an internal
1843 variable of the formatting system (@q{grob property} or @q{layout
1844 property}). The latter is a symbol, so it must be quoted. The
1845 subsection @ref{Modifying properties}, explains what to fill in
1846 for @var{name}, @var{property}, and @var{value}. Here we only
1847 discuss the functionality of this command.
1852 \override Staff.Stem.thickness = #4.0
1856 makes stems thicker (the default is 1.3, with staff line thickness as a
1857 unit). Since the command specifies @code{Staff} as context, it only
1858 applies to the current staff. Other staves will keep their normal
1859 appearance. Here we see the command in action:
1861 @lilypond[quote,fragment,verbatim]
1863 \override Staff.Stem.thickness = #4.0
1869 The @code{\override} command changes the definition of the @code{Stem}
1870 within the current @code{Staff}. After the command is interpreted
1871 all stems are thickened.
1873 Analogous to @code{\set}, the @var{context} argument may be left out,
1874 causing the default context @code{Voice} to be used. Adding
1875 @code{\once} applies the change during one timestep only.
1877 @lilypond[quote,fragment,verbatim]
1879 \once \override Stem.thickness = #4.0
1884 The @code{\override} must be done before the object is
1885 started. Therefore, when altering @emph{Spanner} objects such as slurs
1886 or beams, the @code{\override} command must be executed at the moment
1887 when the object is created. In this example,
1889 @lilypond[quote,fragment,verbatim]
1890 \override Slur.thickness = #3.0
1892 \override Beam.beam-thickness = #0.6
1897 the slur is fatter but the beam is not. This is because the command for
1898 @code{Beam} comes after the Beam is started, so it has no effect.
1900 Analogous to @code{\unset}, the @code{\revert} command for a context
1901 undoes an @code{\override} command; like with @code{\unset}, it only
1902 affects settings that were made in the same context. In other words, the
1903 @code{\revert} in the next example does not do anything.
1906 \override Voice.Stem.thickness = #4.0
1907 \revert Staff.Stem.thickness
1910 Some tweakable options are called @q{subproperties} and reside inside
1911 properties. To tweak those, use commands of the form
1913 @c leave this as a long long
1915 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
1922 \override Stem.details.beamed-lengths = #'(4 4 3)
1928 Internals Reference:
1929 @rinternals{Backend},
1930 @rinternals{All layout objects},
1931 @rinternals{OverrideProperty},
1932 @rinternals{RevertProperty},
1933 @rinternals{PropertySet}.
1936 The back-end is not very strict in type-checking object properties.
1937 Cyclic references in Scheme values for properties can cause hangs
1938 or crashes, or both.
1941 @node The set command
1942 @subsection The @code{@bs{}set} command
1946 @cindex changing properties
1948 Each context has a set of @emph{properties}, variables contained
1949 in that context. Context properties are changed with the @code{\set}
1950 command, which has the following syntax:
1953 \set @var{context}.@var{property} = #@var{value}
1956 @var{value} is a Scheme object, which is why it must be preceded by
1957 the @code{#}@tie{}character.
1959 Contexts properties are usually named in
1960 @code{studlyCaps}. They mostly control the translation from
1961 music to notation, e.g. @code{localAlterations} (for determining
1962 whether to print accidentals), or @code{measurePosition} (for
1963 determining when to print a bar line). Context properties can
1964 change value over time while interpreting a piece of music;
1965 @code{measurePosition} is an obvious example of
1966 this. Context properties are modified with @code{\set}.
1968 For example, multimeasure rests will be combined into a single bar
1969 if the context property @code{skipBars} is set to @code{#t}:
1971 @lilypond[quote,fragment,verbatim]
1973 \set Score.skipBars = ##t
1977 If the @var{context} argument is left out, then the property will be
1978 set in the current bottom context (typically @code{ChordNames},
1979 @code{Voice}, @code{TabVoice}, or @code{Lyrics}).
1981 @lilypond[quote,fragment,verbatim]
1982 \set Score.autoBeaming = ##f
1985 \set autoBeaming = ##t
1993 The change is applied @q{on-the-fly}, during the music, so that the
1994 setting only affects the second group of eighth notes.
1996 Note that the bottom-most context does not always contain the property
1997 that you wish to change -- for example, attempting to set the
1998 @code{skipBars} property of the default bottom context, in this case
1999 @code{Voice}, will have no effect, because skipBars is a property of
2000 the @code{Score} context.
2002 @lilypond[quote,fragment,verbatim]
2008 Contexts are hierarchical, so if an enclosing context was specified, for
2009 example @code{Staff}, then the change would also apply to all
2010 @code{Voice}s in the current staff.
2014 The @code{\unset} command:
2017 \unset @var{context}.@var{property}
2021 is used to remove the definition of @var{property} from
2022 @var{context}. This command removes
2023 the definition only if it is set in @var{context}.
2024 Properties that have been set in enclosing contexts will
2025 not be altered by an unset in an enclosed context:
2027 @lilypond[quote,fragment,verbatim]
2028 \set Score.autoBeaming = ##t
2032 \unset Score.autoBeaming
2040 Like @code{\set}, the @var{context} argument does not have to be
2041 specified for a bottom context, so the two statements
2044 \set Voice.autoBeaming = ##t
2045 \set autoBeaming = ##t
2049 are equivalent if the current bottom context is @code{Voice}.
2053 Preceding a @code{\set} or @code{\unset} command by @code{\once}
2054 makes the setting apply to only a single time-step:
2056 @lilypond[quote,fragment,verbatim]
2058 \once \set fontSize = #4.7
2063 A full description of all available context properties is in the
2064 internals reference, see
2066 @rinternals{Tunable context properties}.
2069 Translation @expansion{} Tunable context properties.
2073 Internals Reference:
2074 @rinternals{Tunable context properties}.
2077 @node The override command
2078 @subsection The @code{\override} command
2080 @cindex grob properties
2081 @cindex properties, grob
2084 There is a special type of context property: the grob
2085 description. Grob descriptions are named in @code{StudlyCaps}
2086 (starting with capital letters). They contain the
2087 @q{default settings} for a particular kind of grob as an
2088 association list. See @file{scm/define-grobs.scm}
2089 to see the settings for each grob description. Grob descriptions
2090 are modified with @code{\override}.
2092 The syntax for the @code{\override} command is
2095 \override [@var{context}.]@var{GrobName}.@var{property} = #@var{value}
2098 For example, we can increase the thickness of a note stem by
2099 overriding the @code{thickness} property of the @code{Stem}
2102 @lilypond[quote,fragment,verbatim]
2104 \override Voice.Stem.thickness = #3.0
2108 If no context is specified in an @code{\override}, the bottom
2111 @lilypond[quote,fragment,verbatim]
2112 \override Staff.Stem.thickness = #3.0
2116 \override Stem.thickness = #0.5
2125 Some tweakable options are called @q{subproperties} and reside inside
2126 properties. To tweak those, use commands in the form
2129 \override Stem.details.beamed-lengths = #'(4 4 3)
2132 or to modify the ends of spanners, use a form like these
2135 \override TextSpanner.bound-details.left.text = #"left text"
2136 \override TextSpanner.bound-details.right.text = #"right text"
2140 @cindex reverting overrides
2141 @cindex overrides, reverting
2143 The effects of @code{\override} can be undone by @code{\revert}.
2145 The syntax for the @code{\revert} command is
2148 \revert [@var{context}.]@var{GrobName}.@var{property}
2153 @lilypond[quote,verbatim]
2156 \override Voice.Stem.thickness = #3.0
2158 \revert Voice.Stem.thickness
2163 The effects of @code{\override} and @code{\revert} apply to all
2164 grobs in the affected context from the current time forward:
2166 @lilypond[quote,verbatim]
2170 \override Staff.Stem.thickness = #3.0
2175 \revert Staff.Stem.thickness
2182 @cindex overriding for only one moment
2184 @code{\once} can be used with @code{\override} or @code{\revert}
2185 to affect only the current time step:
2187 @lilypond[quote,verbatim]
2190 \override Stem.thickness = #3.0
2195 \once \override Stem.thickness = #3.0
2203 Commands which change output generally look like
2206 \override Voice.Stem.thickness = #3.0
2210 To construct this tweak we must determine these bits of information:
2213 @item the context: here @code{Voice}.
2214 @item the layout object: here @code{Stem}.
2215 @item the layout property: here @code{thickness}.
2216 @item a sensible value: here @code{3.0}.
2219 @cindex internal documentation
2220 @cindex finding graphical objects
2221 @cindex graphical object descriptions
2224 @cindex internal documentation
2226 For many properties, regardless of the data type of the property, setting the
2227 property to false (@code{#f}) will result in turning it off, causing
2228 LilyPond to ignore that property entirely. This is particularly useful for
2229 turning off grob properties which may otherwise be causing problems.
2231 We demonstrate how to glean this information from the notation manual
2232 and the program reference.
2236 Internals Reference:
2237 @rinternals{Backend}
2240 @node The tweak command
2241 @subsection The @code{\tweak} command
2246 Changing grob properties
2247 with @code{\override} causes the changes to apply to all of the
2248 given grobs in the context at the moment the change applies.
2249 Sometimes, however, it is desirable to have changes apply to just
2250 one grob, rather than to all grobs in the affected context. This is
2251 accomplished with the @code{\tweak} command, which has the following
2255 \tweak [@var{layout-object}.]@var{grob-property} @var{value}
2258 Specifying @var{layout-object} is optional.
2259 The @code{\tweak} command applies to the music object that immediately
2260 follows @var{value} in the music stream.
2263 In some cases, it is possible to take a short-cut for tuning
2264 graphical objects. For objects that are created directly from
2265 an item in the input file, you can use the @code{\tweak} command.
2268 @lilypond[verbatim,quote]
2274 \tweak duration-log #1
2284 The main use of the @code{\tweak} command is to modify just
2285 one of a number of notation elements which start at the same musical
2286 moment, like the notes of a chord, or tuplet brackets which start
2289 The @code{\tweak} command sets a property in the following object
2290 directly, without requiring the grob name or context to be
2291 specified. For this to work, it is necessary for the @code{\tweak}
2292 command to remain immediately adjacent to the object to which it is
2293 to apply after the input file has been converted to a music stream.
2294 This is often not the case, as many additional elements are inserted
2295 into the music stream implicitly. For example, when a note which is
2296 not part of a chord is processed, LilyPond implicitly inserts a
2297 @code{ChordEvent} event before the note, so separating the tweak
2298 from the note. However, if chord symbols are placed round the
2299 tweak and the note, the @code{\tweak} command comes after the
2300 @code{ChordEvent} in the music stream, so remaining adjacent to the
2301 note, and able to modify it.
2305 @lilypond[verbatim,fragment,quote]
2306 <\tweak color #red c''>4
2312 @lilypond[verbatim,fragment,quote]
2313 \tweak color #red c''4
2318 For an introduction to the syntax and uses of the tweak command
2319 see @rlearning{Tweaking methods}.
2321 When several similar items are placed at the same musical moment,
2322 the @code{\override} command cannot be used to modify just one of
2323 them -- this is where the @code{\tweak} command must be used.
2324 Items which may appear more than once at the same musical moment
2325 include the following:
2327 @c TODO expand to include any further uses of \tweak
2329 @item note heads of notes inside a chord
2330 @item articulation signs on a single note
2331 @item ties between notes in a chord
2332 @item tuplet brackets starting at the same time
2335 @c TODO add examples of these
2337 @cindex chord, modifying one note in
2339 In this example, the color of one note head and the type of another
2340 note head are modified within a single chord:
2342 @lilypond[verbatim,fragment,quote]
2347 \tweak duration-log #1
2352 @code{\tweak} can be used to modify slurs:
2354 @lilypond[verbatim,quote]
2355 \relative { c'-\tweak thickness #5 ( d e f) }
2359 For the @code{\tweak} command to work, it must
2360 remain immediately adjacent to the object to which it is
2361 to apply after the input file has been converted to a music stream.
2362 Tweaking a whole chord does not do anything since its music event
2363 only acts as a container, and all layout objects are created from events
2364 inside of the @code{EventChord}:
2366 @lilypond[verbatim,fragment,quote]
2367 \tweak color #red c''4
2368 \tweak color #red <c'' e''>4
2369 <\tweak color #red c'' e''>4
2372 The simple @code{\tweak} command cannot be used to modify any object
2373 that is not directly created from the input. In particular
2374 it will not affect stems, automatic
2375 beams or accidentals, since these are generated later by
2376 @code{NoteHead} layout objects rather than by music elements in the
2379 Such indirectly created layout objects can be tweaked using the form
2380 of the @code{\tweak} command in which the grob name is specified
2383 @lilypond[fragment,verbatim,quote]
2384 \tweak Stem.color #red
2385 \tweak Beam.color #green c''8 e''
2386 <c'' e'' \tweak Accidental.font-size #-3 ges''>4
2389 @code{\tweak} cannot be used to modify clefs or time
2390 signatures, since these become separated from any preceding
2391 @code{\tweak} command in the input stream by the automatic
2392 insertion of extra elements required to specify the context.
2394 Several @code{\tweak} commands may be placed before a
2395 notational element -- all affect it:
2397 @lilypond[verbatim,fragment,quote]
2399 -\tweak style #'dashed-line
2400 -\tweak dash-fraction #0.2
2401 -\tweak thickness #3
2407 The music stream which is generated from a section of an input file,
2408 including any automatically inserted elements, may be examined,
2409 see @rextend{Displaying music expressions}. This may be helpful in
2410 determining what may be modified by a @code{\tweak} command, or
2411 in determining how to adjust the input to make a @code{\tweak}
2416 @rlearning{Tweaking methods}.
2419 @rextend{Displaying music expressions}.
2423 @cindex tweaking control points
2424 @cindex control points, tweaking
2426 The @code{\tweak} command cannot be used to modify the control
2427 points of just one of several ties in a chord, other than the first
2428 one encountered in the input file.
2430 @node set versus override
2431 @subsection @code{\set} vs. @code{\override}
2433 @c TODO Should't a bunch of that be explained earlier?
2438 The @code{\set} and @code{\override} commands manipulate properties
2439 associated with contexts. In both cases, the properties follow a
2440 @emph{hierarchy of contexts}; properties that are not set themselves in
2441 a context will still show the values of their respective parent's
2444 The lifetime and value of a context property is dynamic and only
2445 available when music is being interpreted (i.e. @q{iterated}). At the
2446 time of the context's creation, properties are initialized from its
2447 corresponding definitions (along with any other modifications) of that
2448 context. Any subsequent changes are achieved with any
2449 @q{property-setting} commands that are within the music itself.
2451 Graphical Object (or @qq{grob}) definitions are a @emph{special}
2452 category of context properties as their structure and use is different
2453 from that of normal context properties. Unlike normal context
2454 properties, grob definitions are subdivided into @emph{grob properties}.
2456 Also, in contrast to normal context properties, grob definitions have
2457 their own internal @q{bookkeeping} used to keep track of their own
2458 individual grob properties and any sub-properties. This means that it
2459 is possible to define those parts within different contexts and yet
2460 still have the overall grob definition at the time of grob creation from
2461 all the pieces provided amongst the current context and its parent(s).
2463 A grob is usually created by an engraver at the time of interpreting a
2464 music expression and receives its initial properties from the current
2465 grob definition of the engraver's context. The engraver (or other
2466 @q{backend} parts of LilyPond) can then change (or add to) the grob's
2467 initial properties. However, this does not affect the context's own
2470 What LilyPond calls @emph{grob properties} in the context of
2471 @q{user-level} tweaks are really the properties of a @emph{context's}
2472 own grob definition.
2474 Grob definitions are accessed with a different set of commands and are
2475 manipulated using @code{\override} and @code{\revert} and have a name
2476 starting with a capital letter (e.g. @samp{NoteHead}); whereas normal
2477 context properties are manipulated using @code{\set} and @code{\unset}
2478 and are named starting with a lowercase letter.
2480 @cindex tweak, relation to @code{\override}
2482 @funindex \overrideProperty
2484 The commands @code{\tweak} and @code{\overrideProperty} change grob
2485 properties by bypassing all context properties completely and, instead,
2486 catch grobs as they are being created, setting properties on them for
2487 a music event (@code{\tweak}) or, in the case of
2488 @code{\overrideProperty} for a specific override.
2491 @node Modifying alists
2492 @subsection Modifying alists
2494 Some user-configurable properties are internally represented as
2495 @emph{alists} (association lists), which store pairs of
2496 @emph{keys} and @emph{values}. The structure of an alist is:
2499 '((@var{key1} . @var{value1})
2500 (@var{key2} . @var{value2})
2501 (@var{key3} . @var{value3})
2505 If an alist is a grob property or @code{\paper} variable, its keys
2506 can be modified individually without affecting other keys.
2508 For example, to reduce the space between adjacent staves in a
2509 staff-group, use the @code{staff-staff-spacing} property of the
2510 @code{StaffGrouper} grob. The property is an alist with four
2511 keys: @code{basic-distance}, @code{minimum-distance},
2512 @code{padding}, and @code{stretchability}. The standard settings
2513 for this property are listed in the @qq{Backend} section of the
2514 Internals Reference (see @rinternals{StaffGrouper}):
2517 '((basic-distance . 9)
2518 (minimum-distance . 7)
2520 (stretchability . 5))
2523 One way to bring the staves closer together is by reducing the
2524 value of the @code{basic-distance} key (@code{9}) to match the
2525 value of @code{minimum-distance} (@code{7}). To modify a single
2526 key individually, use a @emph{nested declaration}:
2528 @lilypond[quote,verbatim]
2529 % default space between staves
2531 \new Staff { \clef treble c''1 }
2532 \new Staff { \clef bass c1 }
2535 % reduced space between staves
2536 \new PianoStaff \with {
2537 % this is the nested declaration
2538 \override StaffGrouper.staff-staff-spacing.basic-distance = #7
2540 \new Staff { \clef treble c''1 }
2541 \new Staff { \clef bass c1 }
2545 Using a nested declaration will update the specified key (such as
2546 @code{basic-distance} in the above example) without altering any
2547 other keys already set for the same property.
2549 Now suppose we want the staves to be as close as possible without
2550 overlapping. The simplest way to do this is to set all four alist
2551 keys to zero. However, it is not necessary to enter four nested
2552 declarations, one for each key. Instead, the property can be
2553 completely re-defined with one declaration, as an alist:
2555 @lilypond[quote,verbatim]
2556 \new PianoStaff \with {
2557 \override StaffGrouper.staff-staff-spacing =
2558 #'((basic-distance . 0)
2559 (minimum-distance . 0)
2561 (stretchability . 0))
2563 \new Staff { \clef treble c''1 }
2564 \new Staff { \clef bass c1 }
2568 Note that any keys not explicitly listed in the alist definition
2569 will be reset to their @emph{default-when-unset} values. In the
2570 case of @code{staff-staff-spacing}, any unset key-values would be
2571 reset to zero (except @code{stretchability}, which takes the value
2572 of @code{basic-distance} when unset). Thus the following two
2573 declarations are equivalent:
2576 \override StaffGrouper.staff-staff-spacing =
2577 #'((basic-distance . 7))
2579 \override StaffGrouper.staff-staff-spacing =
2580 #'((basic-distance . 7)
2581 (minimum-distance . 0)
2583 (stretchability . 7))
2586 One (possibly unintended) consequence of this is the removal of
2587 any standard settings that are set in an initialization file and
2588 loaded each time an input file is compiled. In the above example,
2589 the standard settings for @code{padding} and
2590 @code{minimum-distance} (defined in @file{scm/define-grobs.scm})
2591 are reset to their default-when-unset values (zero for both keys).
2592 Defining a property or variable as an alist (of any size) will
2593 always reset all unset key-values to their default-when-unset
2594 values. Unless this is the intended result, it is safer to update
2595 key-values individually with a nested declaration.
2597 @warning{Nested declarations will not work for context property
2598 alists (such as @code{beamExceptions}, @code{keyAlterations},
2599 @code{timeSignatureSettings}, etc.). These properties can only be
2600 modified by completely re-defining them as alists.}
2603 @node Useful concepts and properties
2604 @section Useful concepts and properties
2609 * Direction and placement::
2610 * Distances and measurements::
2612 * Staff symbol properties::
2614 * Visibility of objects::
2616 * Rotating objects::
2620 @subsection Input modes
2622 The way in which the notation contained within an input file is
2623 interpreted is determined by the current input mode.
2625 @subsubsubheading Chord mode
2627 This is activated with the @code{\chordmode} command, and causes
2628 input to be interpreted with the syntax of chord notation, see
2629 @ref{Chord notation}. Chords are rendered as notes on a staff.
2631 Chord mode is also activated with the @code{\chords} command.
2632 This also creates a new @code{ChordNames} context and
2633 causes the following input to be interpreted with the syntax of
2634 chord notation and rendered as chord names in the @code{ChordNames}
2635 context, see @ref{Printing chord names}.
2637 @subsubsubheading Drum mode
2639 This is activated with the @code{\drummode} command, and causes
2640 input to be interpreted with the syntax of drum notation, see
2641 @ref{Basic percussion notation}.
2643 Drum mode is also activated with the @code{\drums} command.
2644 This also creates a new @code{DrumStaff} context and causes the
2645 following input to be interpreted with the syntax of drum notation
2646 and rendered as drum symbols on a drum staff, see
2647 @ref{Basic percussion notation}.
2649 @subsubsubheading Figure mode
2651 This is activated with the @code{\figuremode} command, and causes
2652 input to be interpreted with the syntax of figured bass, see
2653 @ref{Entering figured bass}.
2655 Figure mode is also activated with the @code{\figures} command.
2656 This also creates a new @code{FiguredBass} context and causes the
2657 following input to be interpreted with the figured bass syntax
2658 and rendered as figured bass symbols in the @code{FiguredBass}
2659 context, see @ref{Introduction to figured bass}.
2661 @subsubsubheading Fret and tab modes
2663 There are no special input modes for entering fret and tab symbols.
2665 To create tab diagrams, enter notes or chords in note mode and
2666 render them in a @code{TabStaff} context, see
2667 @ref{Default tablatures}.
2669 To create fret diagrams above a staff, you have two choices.
2670 You can either use the @code{FretBoards} context (see
2671 @ref{Automatic fret diagrams}) or you can enter them as a markup
2672 above the notes using the @code{\fret-diagram} command (see
2673 @ref{Fret diagram markups}).
2675 @subsubsubheading Lyrics mode
2677 This is activated with the @code{\lyricmode} command, and causes
2678 input to be interpreted as lyric syllables with optional durations
2679 and associated lyric modifiers, see @ref{Vocal music}.
2681 Lyric mode is also activated with the @code{\addlyrics} command.
2682 This also creates a new @code{Lyrics} context and an implicit
2683 @code{\lyricsto} command which associates the following lyrics
2684 with the preceding music.
2686 @subsubsubheading Markup mode
2688 This is activated with the @code{\markup} command, and causes
2689 input to be interpreted with the syntax of markup, see
2690 @ref{Text markup commands}.
2692 @subsubsubheading Note mode
2694 This is the default mode or it may be activated with the
2695 @code{\notemode} command. Input is interpreted as pitches,
2696 durations, markup, etc and typeset as musical notation on a staff.
2698 It is not normally necessary to specify note mode explicitly, but
2699 it may be useful to do so in certain situations, for example if you
2700 are in lyric mode, chord mode or any other mode and want to insert
2701 something that only can be done with note mode syntax.
2704 @node Direction and placement
2705 @subsection Direction and placement
2707 In typesetting music the direction and placement of many items is
2708 a matter of choice. For example, the stems of notes can
2709 be directed up or down; lyrics, dynamics, and other expressive
2710 marks may be placed above or below the staff; text may be aligned
2711 left, right or center; etc. Most of these choices may be left to
2712 be determined automatically by LilyPond, but in some cases it may
2713 be desirable to force a particular direction or placement.
2716 * Articulation direction indicators::
2717 * The direction property::
2721 @node Articulation direction indicators
2722 @unnumberedsubsubsec Articulation direction indicators
2724 By default some directions are always up or always down (e.g.
2725 dynamics or fermata), while other things can alternate between
2726 up or down based on the stem direction (like slurs or accents).
2728 @c TODO Add table showing these
2730 The default action may be overridden by prefixing the articulation
2731 by a @emph{direction indicator}. Three direction indicators are
2732 available: @code{^} (meaning @qq{up}), @code{_} (meaning @qq{down})
2733 and @code{-} (meaning @qq{use default direction}). The direction
2734 indicator can usually be omitted, in which case @code{-} is assumed,
2735 but a direction indicator is @strong{always} required before
2738 @item @code{\tweak} commands
2739 @item @code{\markup} commands
2740 @item @code{\tag} commands
2741 @item string markups, e.g. -"string"
2742 @item fingering instructions, e.g. @w{@code{-1}}
2743 @item articulation shortcuts, e.g. @w{@code{-.}}, @w{@code{->}}, @w{@code{--}}
2746 Direction indicators affect only the next note:
2748 @lilypond[verbatim,quote]
2758 @node The direction property
2759 @unnumberedsubsubsec The direction property
2761 The position or direction of many layout objects is controlled by the
2762 @code{direction} property.
2764 The value of the @code{direction} property may be set to @code{1},
2765 meaning @qq{up} or @qq{above}, or to @w{@code{-1}}, meaning @qq{down} or
2766 @qq{below}. The symbols @code{UP} and @code{DOWN} may be used instead
2767 of @code{1} and @w{@code{-1}} respectively. The default direction may
2768 be specified by setting @code{direction} to @code{0} or @code{CENTER}.
2769 Alternatively, in many cases predefined commands exist to specify the
2770 direction. These are of the form
2773 @code{\xxxUp}, @code{\xxxDown} or @code{\xxxNeutral}
2777 where @code{\xxxNeutral} means @qq{use the default} direction.
2778 See @rlearning{Within-staff objects}.
2780 In a few cases, arpeggio for example, the value of the @code{direction}
2781 property can specify whether the object is to be placed to the right or
2782 left of the parent. In this case @w{@code{-1}} or @code{LEFT} means
2783 @qq{to the left} and @code{1} or @code{RIGHT} means @qq{to the right}.
2784 @code{0} or @code{CENTER} means @qq{use the default} direction.
2787 These all have side-axis set to #X
2788 AmbitusAccidental - direction has no effect
2790 StanzaNumber - not tried
2791 TrillPitchAccidental - not tried
2792 TrillPitchGroup - not tried
2795 These indications affect all notes until they are canceled.
2797 @lilypond[verbatim,quote]
2808 In polyphonic music, it is generally better to specify an explicit
2809 @code{voice} than change an object's direction. For more information,
2810 see @ref{Multiple voices}.
2814 @rlearning{Within-staff objects}.
2817 @ref{Multiple voices}.
2820 @node Distances and measurements
2821 @subsection Distances and measurements
2823 @cindex distances, absolute
2824 @cindex distances, scaled
2831 Distances in LilyPond are of two types: absolute and scaled.
2833 Absolute distances are used for specifying margins, indents, and
2834 other page layout details, and are by default specified in
2835 millimeters. Distances may be specified in other units by
2836 following the quantity by @code{\mm}, @code{\cm},
2837 @code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27 of
2838 an inch). Page layout distances can also be specified in scalable
2839 units (see the following paragraph) by appending
2840 @code{\staff-space} to the quantity. Page layout is described in
2841 detail in @ref{Page layout}.
2843 Scaled distances are always specified in units of the staff-space
2844 or, rarely, the half staff-space. The staff-space is the distance
2845 between two adjacent staff lines. The default value can be changed
2846 globally by setting the global staff size, or it can be overridden
2847 locally by changing the @code{staff-space} property of
2848 @code{StaffSymbol}. Scaled distances automatically scale with any
2849 change to the either the global staff size or the
2850 @code{staff-space} property of @code{StaffSymbol}, but fonts scale
2851 automatically only with changes to the global staff size.
2852 The global staff size thus enables the overall size of a rendered
2853 score to be easily varied. For the methods of setting the global
2854 staff size see @ref{Setting the staff size}.
2858 If just a section of a score needs to be rendered to a different
2859 scale, for example an ossia section or a footnote, the global staff
2860 size cannot simply be changed as this would affect the entire score.
2861 In such cases the change in size is made by overriding both the
2862 @code{staff-space} property of @code{StaffSymbol} and the size of
2863 the fonts. A Scheme function, @code{magstep}, is available to
2864 convert from a font size change to the equivalent change in
2865 @code{staff-space}. For an explanation and an example of its use,
2866 see @rlearning{Length and thickness of objects}.
2870 @rlearning{Length and thickness of objects}.
2874 @ref{Setting the staff size}.
2878 @subsection Dimensions
2881 @cindex bounding box
2883 The dimensions of a graphical object specify the positions of the left
2884 and right edges and the bottom and top edges of the objects' bounding
2885 box as distances from the objects' reference point in units of
2886 staff-spaces. These positions are usually coded as two Scheme pairs.
2887 For example, the text markup command @code{\with-dimensions} takes
2888 three arguments, the first two of which are a Scheme pair giving the
2889 left and right edge positions and a Scheme pair giving the bottom and
2893 \with-dimensions #'(-5 . 10) #'(-3 . 15) @var{arg}
2896 This specifies a bounding box for @var{arg} with its left edge at -5,
2897 its right edge at 10, its bottom edge at -3 and its top edge at 15,
2898 all measured from the objects' reference point in units of
2903 @ref{Distances and measurements}.
2906 @node Staff symbol properties
2907 @subsection Staff symbol properties
2909 @cindex adjusting staff symbol
2910 @cindex drawing staff symbol
2911 @cindex staff symbol, setting of
2913 @c TODO Extend or remove this section. See also NR 1.6.2 Staff symbol
2914 @c Need to think of uses for these properties. Eg 'line-positions
2915 @c is used in a snippet to thicken centre line.
2916 @c If retained, add @ref to here in 1.6.2 -td
2918 The vertical position of staff lines and the number of staff lines
2919 can be defined at the same time. As the following example shows,
2920 note positions are not influenced by the staff line positions.
2922 @warning{The @code{'line-positions} property overrides the
2923 @code{'line-count} property. The number of staff lines is
2924 implicitly defined by the number of elements in the list of values
2925 for @code{'line-positions}.}
2927 @lilypond[verbatim,quote]
2929 \override StaffSymbol.line-positions = #'(7 3 0 -4 -6 -7)
2931 \relative { a4 e' f b | d1 }
2934 The width of a staff can be modified. The units are staff
2935 spaces. The spacing of objects inside the staff is not affected by
2938 @lilypond[verbatim,quote]
2940 \override StaffSymbol.width = #23
2942 \relative { a4 e' f b | d1 }
2947 @subsection Spanners
2949 Many objects of musical notation extend over several notes or even
2950 several bars. Examples are slurs, beams, tuplet brackets, volta
2951 repeat brackets, crescendi, trills, and glissandi. Such objects
2952 are collectively called @qq{spanners}, and have special properties to control
2953 their appearance and behaviour. Some of these properties are common
2954 to all spanners; others are restricted to a sub-set of the spanners.
2956 All spanners support the @code{spanner-interface}. A few, essentially
2957 those that draw a straight line between the two objects, support in
2958 addition the @code{line-spanner-interface}.
2961 * Using the spanner-interface::
2962 * Using the line-spanner-interface::
2965 @node Using the spanner-interface
2966 @unnumberedsubsubsec Using the @code{spanner-interface}
2968 This interface provides two properties that apply to several spanners.
2970 @subsubsubheading The @code{minimum-length} property
2972 The minimum length of the spanner is specified by the
2973 @code{minimum-length} property. Increasing this usually has the
2974 necessary effect of increasing the spacing of the notes between the
2975 two end points. However, this override has no effect on
2976 many spanners, as their length is determined by other considerations.
2977 A few examples where it is effective are shown below.
2987 Works as long as callback is made:
2991 Works not at all for:
3000 @lilypond[verbatim,quote,fragment]
3003 % increase the length of the tie
3004 -\tweak minimum-length #5
3008 @lilypond[verbatim,quote]
3009 \relative \compressMMRests {
3012 % increase the length of the rest bar
3013 \once \override MultiMeasureRest.minimum-length = #20
3019 @lilypond[verbatim,quote]
3022 % increase the length of the hairpin
3023 \override Hairpin.minimum-length = #20
3028 This override can also be used to increase the length of slurs and
3031 @lilypond[verbatim,quote]
3035 -\tweak minimum-length #5
3040 -\tweak minimum-length #5
3045 For some layout objects, the @code{minimum-length} property becomes
3046 effective only if the @code{set-spacing-rods} procedure is called
3047 explicitly. To do this, the @code{springs-and-rods} property should
3048 be set to @code{ly:spanner::set-spacing-rods}. For example,
3049 the minimum length of a glissando has no effect unless the
3050 @code{springs-and-rods} property is set:
3052 @lilypond[verbatim,fragment,quote]
3056 % not effective alone
3057 \once \override Glissando.minimum-length = #20
3060 % effective only when both overrides are present
3061 \once \override Glissando.minimum-length = #20
3062 \once \override Glissando.springs-and-rods = #ly:spanner::set-spacing-rods
3066 The same is true of the @code{Beam} object:
3068 @lilypond[verbatim,fragment,quote]
3069 % not effective alone
3070 \once \override Beam.minimum-length = #20
3073 % effective only when both overrides are present
3074 \once \override Beam.minimum-length = #20
3075 \once \override Beam.springs-and-rods = #ly:spanner::set-spacing-rods
3079 @subsubsubheading The @code{to-barline} property
3081 The second useful property of the @code{spanner-interface} is
3082 @code{to-barline}. By default this is true, causing hairpins and
3083 other spanners which are terminated on the first note of a measure to
3084 end instead on the immediately preceding bar line. If set to false,
3085 the spanner will extend beyond the bar line and end on the note
3088 @lilypond[verbatim,quote]
3090 a' \< a a a a \! a a a \break
3091 \override Hairpin.to-barline = ##f
3092 a \< a a a a \! a a a
3096 This property is not effective for all spanners. For example,
3097 setting it to @code{#t} has no effect on slurs or phrasing slurs
3098 or on other spanners for which terminating on the bar line would
3101 @node Using the line-spanner-interface
3102 @unnumberedsubsubsec Using the @code{line-spanner-interface}
3104 Objects which support the @code{line-spanner-interface} include
3107 @item @code{DynamicTextSpanner}
3108 @item @code{Glissando}
3109 @item @code{TextSpanner}
3110 @item @code{TrillSpanner}
3111 @item @code{VoiceFollower}
3114 The routine responsible for drawing the stencils for these spanners is
3115 @code{ly:line-spanner::print}. This routine determines the
3116 exact location of the two end points and draws a line
3117 between them, in the style requested. The locations of the two
3118 end points of the spanner are computed on-the-fly, but it is
3119 possible to override their Y-coordinates. The
3120 properties which need to be specified are nested
3121 two levels down within the property hierarchy, but the syntax of
3122 the @code{\override} command is quite simple:
3124 @lilypond[quote,fragment,verbatim]
3126 \once \override Glissando.bound-details.left.Y = #3
3127 \once \override Glissando.bound-details.right.Y = #-2
3131 The units for the @code{Y} property are @code{staff-space}s,
3132 with the center line of the staff being the zero point.
3133 For the glissando, this is the value for @code{Y} at the
3134 X-coordinate corresponding to the center point of each note head,
3135 if the line is imagined to be extended to there.
3137 If @code{Y} is not set, the value is computed from the vertical
3138 position of the corresponding attachment point of the spanner.
3140 In case of a line break, the values for the end points are
3141 specified by the @code{left-broken} and @code{right-broken}
3142 sub-lists of @code{bound-details}. For example:
3144 @lilypond[ragged-right,fragment,verbatim,quote]
3145 \override Glissando.breakable = ##t
3146 \override Glissando.bound-details.right-broken.Y = #-3
3147 c''1 \glissando \break
3152 A number of further properties of the @code{left} and
3153 @code{right} sub-lists of the @code{bound-details} property
3154 may be modified in the same way as @code{Y}:
3158 This sets the Y-coordinate of the end point, in @code{staff-space}s
3159 offset from the staff center line. By default, it is the center of
3160 the bound object, so a glissando points to the vertical center of
3163 For horizontal spanners, such as text spanners and trill spanners,
3164 it is hardcoded to 0.
3167 This determines where the line starts and ends in the X-direction,
3168 relative to the bound object. So, a value of @w{@code{-1}} (or
3169 @code{LEFT}) makes the line start/end at the left side of the note
3170 head it is attached to.
3173 This is the absolute X-coordinate of the end point. It is usually
3174 computed on the fly, and overriding it has little useful effect.
3177 Line spanners may have symbols at the beginning or end, which is
3178 contained in this sub-property. This is for internal use; it is
3179 recommended that @code{text} be used instead.
3182 This is a markup that is evaluated to yield the stencil. It is used
3183 to put @i{cresc.}, @i{tr} and other text on horizontal spanners.
3185 @lilypond[quote,ragged-right,fragment,verbatim]
3186 \override TextSpanner.bound-details.left.text
3187 = \markup { \small \bold Slower }
3188 \relative { c''2\startTextSpan b c a\stopTextSpan }
3191 @item stencil-align-dir-y
3192 @item stencil-offset
3193 Without setting one of these, the stencil is simply put at the
3194 end-point, centered on the line, as defined by the @code{X} and
3195 @code{Y} sub-properties. Setting either @code{stencil-align-dir-y}
3196 or @code{stencil-offset} will move the symbol at the edge vertically
3197 relative to the end point of the line:
3199 @lilypond[quote,fragment,verbatim]
3200 \override TextSpanner.bound-details.left.stencil-align-dir-y = #-2
3201 \override TextSpanner.bound-details.right.stencil-align-dir-y = #UP
3203 \override TextSpanner.bound-details.left.text = #"ggg"
3204 \override TextSpanner.bound-details.right.text = #"hhh"
3206 \relative { c'4^\startTextSpan c c c \stopTextSpan }
3209 Note that negative values move the text @emph{up}, contrary to the
3210 effect that might be expected, as a value of @w{@code{-1}} or
3211 @code{DOWN} means align the @emph{bottom} edge of the text with
3212 the spanner line. A value of @code{1} or @code{UP} aligns
3213 the top edge of the text with the spanner line.
3216 Setting this sub-property to @code{#t} produces an arrowhead at the
3217 end-points of the line.
3220 This sub-property controls the space between the specified
3221 end point of the line and the actual end. Without padding, a
3222 glissando would start and end in the center of each note head.
3226 The music function @code{\endSpanners} terminates the spanner
3227 which starts on the immediately following note prematurely. It
3228 is terminated after exactly one note, or at the following bar line
3229 if @code{to-barline} is true and a bar line occurs before the next
3232 @lilypond[verbatim,quote,ragged-right]
3235 c2 \startTextSpan c2 c2
3241 When using @code{\endSpanners} it is not necessary to close
3242 \startTextSpan with \stopTextSpan, nor is it necessary to close
3243 hairpins with @code{\!}.
3246 Internals Reference:
3247 @rinternals{TextSpanner},
3248 @rinternals{Glissando},
3249 @rinternals{VoiceFollower},
3250 @rinternals{TrillSpanner},
3251 @rinternals{line-spanner-interface}.
3254 @node Visibility of objects
3255 @subsection Visibility of objects
3257 @cindex objects, visibility of
3258 @cindex grobs, visibility of
3259 @cindex visibility of objects
3261 There are four main ways in which the visibility of layout objects
3262 can be controlled: their stencil can be removed, they can be made
3263 transparent, they can be colored white, or their
3264 @code{break-visibility} property can be overridden. The first
3265 three apply to all layout objects; the last to just a few -- the
3266 @emph{breakable} objects. The Learning Manual introduces these
3267 four techniques, see @rlearning{Visibility and color of objects}.
3269 There are also a few other techniques which are specific to
3270 certain layout objects. These are covered under Special
3274 * Removing the stencil::
3275 * Making objects transparent::
3276 * Painting objects white::
3277 * Using break-visibility::
3278 * Special considerations::
3282 @node Removing the stencil
3283 @unnumberedsubsubsec Removing the stencil
3285 @cindex stencil, removing
3288 Every layout object has a stencil property. By default this is set
3289 to the specific function which draws that object. If this property
3290 is overridden to @code{#f} no function will be called and the object
3291 will not be drawn. The default action can be recovered with
3294 @lilypond[quote,fragment,verbatim]
3296 \override Score.BarLine.stencil = ##f
3298 \revert Score.BarLine.stencil
3302 This rather common operation has a shortcut @code{\omit}:
3304 @lilypond[quote,fragment,verbatim]
3308 \undo \omit Score.BarLine
3312 @node Making objects transparent
3313 @unnumberedsubsubsec Making objects transparent
3315 @cindex transparent, making objects
3318 Every layout object has a transparent property which by default is
3319 set to @code{#f}. If set to @code{#t} the object still occupies
3320 space but is made invisible.
3322 @lilypond[quote,fragment,verbatim]
3324 \once \override NoteHead.transparent = ##t
3328 This rather common operation has a shortcut @code{\hide}:
3330 @lilypond[quote,fragment,verbatim]
3332 \once \hide NoteHead
3336 @node Painting objects white
3337 @unnumberedsubsubsec Painting objects white
3339 @cindex objects, coloring
3340 @cindex coloring objects
3342 @cindex printing order
3343 @cindex overwriting objects
3344 @cindex objects, overwriting
3345 @cindex grobs, overwriting
3347 Every layout object has a color property which by default is set
3348 to @code{black}. If this is overridden to @code{white} the object
3349 will be indistinguishable from the white background. However,
3350 if the object crosses other objects the color of the crossing
3351 points will be determined by the order in which they are drawn,
3352 and this may leave a ghostly image of the white object, as shown
3355 @lilypond[quote,fragment,verbatim]
3356 \override Staff.Clef.color = #white
3360 This may be avoided by changing the order of printing the objects.
3361 All layout objects have a @code{layer} property which should be set
3362 to an integer. Objects with the lowest value of @code{layer} are
3363 drawn first, then objects with progressively higher values are drawn,
3364 so objects with higher values overwrite objects with lower values.
3365 By default most objects are assigned a @code{layer} value of
3366 @code{1}, although a few objects, including @code{StaffSymbol} and
3367 @code{BarLine}, are assigned a value of @code{0}. The order of
3368 printing objects with the same value of @code{layer} is indeterminate.
3370 In the example above the white clef, with a default @code{layer}
3371 value of @code{1}, is drawn after the staff lines (default
3372 @code{layer} value @code{0}), so overwriting them. To change this,
3373 the @code{Clef} object must be given in a lower value of
3374 @code{layer}, say @w{@code{-1}}, so that it is drawn earlier:
3376 @lilypond[quote,fragment,verbatim]
3377 \override Staff.Clef.color = #white
3378 \override Staff.Clef.layer = #-1
3382 @node Using break-visibility
3383 @unnumberedsubsubsec Using break-visibility
3385 @c TODO Add making other objects breakable
3387 @cindex break-visibility
3389 Most layout objects are printed only once, but some like
3390 bar lines, clefs, time signatures and key signatures, may need
3391 to be printed twice when a line break occurs -- once at the end
3392 of the line and again at the start of the next line. Such
3393 objects are called @emph{breakable}, and have a property, the
3394 @code{break-visibility} property to control their visibility
3395 at the three positions in which they may appear -- at the
3396 start of a line, within a line if they are changed, and at the
3397 end of a line if a change takes place there.
3399 For example, the time signature
3400 by default will be printed at the start of the first line, but
3401 nowhere else unless it changes, when it will be printed at the
3402 point at which the change occurs. If this change occurs at the
3403 end of a line the new time signature will be printed at the start
3404 of the next line and a cautionary time signature will be printed
3405 at the end of the previous line as well.
3407 This behaviour is controlled by the @code{break-visibility}
3408 property, which is explained in
3409 @c Leave this ref on a newline - formats incorrectly otherwise -td
3410 @rlearning{Visibility and color of objects}. This property takes
3411 a vector of three booleans which, in order, determine whether the
3412 object is printed at the end of, within the body of, or at the
3413 beginning of a line. Or to be more precise, before a line break,
3414 where there is no line break, or after a line break.
3416 Alternatively, these eight combinations may be specified
3417 by pre-defined functions, defined in @file{scm/output-lib.scm},
3418 where the last three columns indicate whether the layout objects
3419 will be visible in the positions shown at the head of the columns:
3421 @multitable {@code{begin-of-line-invisible}} {@code{#(#t #t #t)}} {Before} {At no} {After}
3422 @headitem Function @tab Vector @tab Before @tab At no @tab After
3423 @headitem form @tab form @tab break @tab break @tab break
3425 @item @code{all-visible} @tab @code{#(#t #t #t)} @tab yes @tab yes @tab yes
3426 @item @code{begin-of-line-visible} @tab @code{#(#f #f #t)} @tab no @tab no @tab yes
3427 @item @code{center-visible} @tab @code{#(#f #t #f)} @tab no @tab yes @tab no
3428 @item @code{end-of-line-visible} @tab @code{#(#t #f #f)} @tab yes @tab no @tab no
3429 @item @code{begin-of-line-invisible} @tab @code{#(#t #t #f)} @tab yes @tab yes @tab no
3430 @item @code{center-invisible} @tab @code{#(#t #f #t)} @tab yes @tab no @tab yes
3431 @item @code{end-of-line-invisible} @tab @code{#(#f #t #t)} @tab no @tab yes @tab yes
3432 @item @code{all-invisible} @tab @code{#(#f #f #f)} @tab no @tab no @tab no
3435 The default settings of @code{break-visibility} depend on the
3436 layout object. The following table shows all the layout objects
3437 of interest which are affected by @code{break-visibility} and the
3438 default setting of this property:
3440 @multitable @columnfractions .3 .3 .4
3442 @headitem Layout object @tab Usual context @tab Default setting
3444 @c omit Ambitus as it appears not to be affected by break-visibility -td
3445 @c @item @code{Ambitus} @tab as specified @tab @code{begin-of-line-visible}
3446 @item @code{BarLine} @tab @code{Score} @tab calculated
3447 @item @code{BarNumber} @tab @code{Score} @tab @code{begin-of-line-visible}
3448 @c omit the following item until it can be explained -td
3449 @c @item @code{BreakAlignGroup} @tab @code{Score} @tab calculated
3450 @item @code{BreathingSign} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3451 @item @code{Clef} @tab @code{Staff} @tab @code{begin-of-line-visible}
3452 @item @code{Custos} @tab @code{Staff} @tab @code{end-of-line-visible}
3453 @item @code{DoublePercentRepeat} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3454 @item @code{KeyCancellation} @tab @code{Staff} @tab @code{begin-of-line-invisible}
3455 @item @code{KeySignature} @tab @code{Staff} @tab @code{begin-of-line-visible}
3456 @c omit LeftEdge until it can be explained -td
3457 @c @item @code{LeftEdge} @tab @code{Score} @tab @code{center-invisible}
3458 @item @code{ClefModifier} @tab @code{Staff} @tab @code{begin-of-line-visible}
3459 @item @code{RehearsalMark} @tab @code{Score} @tab @code{end-of-line-invisible}
3460 @item @code{TimeSignature} @tab @code{Staff} @tab @code{all-visible}
3464 The example below shows the use of the vector form to control the
3465 visibility of bar lines:
3467 @lilypond[quote,verbatim,ragged-right]
3471 % Remove bar line at the end of the current line
3472 \once \override Score.BarLine.break-visibility = ##(#f #t #t)
3479 Although all three components of the vector used to override
3480 @code{break-visibility} must be present, not all of them are
3481 effective with every layout object, and some combinations may
3482 even give errors. The following limitations apply:
3485 @item Bar lines cannot be printed at the start of line.
3487 @item A bar number cannot be printed at the start of the @emph{first}
3488 line unless it is set to be different from @code{1}.
3490 @item Clef -- see the next section.
3492 @item Double percent repeats are either @emph{all printed} or
3493 @emph{all suppressed}. Use @code{begin-of-line-invisible}
3494 to print them and @code{all-invisible} to suppress them.
3496 @item Key signature -- see the next section.
3498 @item ClefModifier -- see the next section.
3502 @node Special considerations
3503 @unnumberedsubsubsec Special considerations
3505 @subsubsubheading Visibility following explicit changes
3507 @cindex key signature, visibility following explicit change
3508 @cindex explicitKeySignatureVisibility
3509 @cindex clef, visibility following explicit change
3510 @cindex explicitClefVisibility
3512 The @code{break-visibility} property controls the visibility of
3513 key signatures and changes of clef only at the start of lines,
3514 i.e. after a break. It has no effect on the visibility of the
3515 key signature or clef following an explicit key change or an
3516 explicit clef change within or at the end of a line. In the
3517 following example the key signature following the explicit change
3518 to B-flat major is still visible, even though @code{all-invisible}
3521 @lilypond[quote,verbatim,ragged-right]
3525 % Try to remove all key signatures
3526 \override Staff.KeySignature.break-visibility = #all-invisible
3535 The visibility of such explicit key signature and clef changes is
3536 controlled by the @code{explicitKeySignatureVisibility} and
3537 @code{explicitClefVisibility} properties. These are the equivalent
3538 of the @code{break-visibility} property and both take a vector of
3539 three booleans or the predefined functions listed above, exactly like
3540 @code{break-visibility}. Both are properties of the Staff context,
3541 not the layout objects themselves, and so they are set using the
3542 @code{\set} command. Both are set by default to @code{all-visible}.
3543 These properties control only the visibility of key signatures and
3544 clefs resulting from explicit changes and do not affect key
3545 signatures and clefs at the beginning of lines;
3546 @code{break-visibility} must still be overridden in the appropriate
3547 object to remove these.
3549 @lilypond[quote,verbatim,ragged-right]
3553 \set Staff.explicitKeySignatureVisibility = #all-invisible
3554 \override Staff.KeySignature.break-visibility = #all-invisible
3562 @subsubsubheading Visibility of cancelling accidentals
3564 To remove the cancelling accidentals printed at an explicit key
3565 change, set the Staff context property @code{printKeyCancellation}
3568 @lilypond[quote,verbatim,ragged-right]
3572 \set Staff.explicitKeySignatureVisibility = #all-invisible
3573 \set Staff.printKeyCancellation = ##f
3574 \override Staff.KeySignature.break-visibility = #all-invisible
3582 With these overrides only the accidentals before the notes remain
3583 to indicate the change of key.
3585 Note that when changing the key to C@tie{}major or A@tie{}minor
3586 the cancelling accidentals would be the @emph{only} indication of
3587 the key change. In this case setting @code{printKeyCancellation} to
3588 @code{#f} has no effect:
3590 @lilypond[quote,verbatim,ragged-right]
3594 \set Staff.explicitKeySignatureVisibility = #all-invisible
3595 \set Staff.printKeyCancellation = ##f
3603 To suppress the cancelling accidentals even when the key is
3604 changed to C@tie{}major or A@tie{}minor, override
3605 the visibility of the @code{KeyCancellation} grob instead:
3607 @lilypond[quote,verbatim,ragged-right]
3611 \set Staff.explicitKeySignatureVisibility = #all-invisible
3612 \override Staff.KeyCancellation.break-visibility = #all-invisible
3620 @c TODO Add visibility of cautionary accidentals before notes
3622 @subsubsubheading Automatic bars
3624 @cindex automaticBars
3625 @cindex bar lines, suppressing
3627 As a special case, the printing of bar lines can also be turned off
3628 by setting the @code{automaticBars} property in the Score context.
3629 If set to @code{#f}, bar lines will not be printed automatically;
3630 they must be explicitly created with a @code{\bar} command. Unlike
3631 the @code{\cadenzaOn} predefined command, measures are still counted.
3632 Bar generation will resume according to that count if this property
3633 is later set to @code{#t}. When set to @code{#f}, line breaks can
3634 occur only at explicit @code{\bar} commands.
3638 @subsubsubheading Transposed clefs
3640 @cindex transposed clefs, visibility of
3641 @cindex visibility of transposed clefs
3642 @cindex clefs, visibility of transposition
3644 The small transposition symbol on transposed clefs is produced by the
3645 @code{ClefModifier} layout object. Its visibility is automatically
3646 inherited from the @code{Clef} object, so it is not necessary to apply
3647 any required @code{break-visibility} overrides to the @code{ClefModifier}
3648 layout objects to suppress transposition symbols for invisible clefs.
3650 For explicit clef changes, the @code{explicitClefVisibility}
3651 property controls both the clef symbol and any transposition symbol
3656 @rlearning{Visibility and color of objects}.
3660 @subsection Line styles
3662 Some performance indications, e.g., @i{rallentando} and
3663 @i{accelerando} and @i{trills} are written as text and are
3664 extended over many measures with lines, sometimes dotted or wavy.
3666 These all use the same routines as the glissando for drawing the
3667 texts and the lines, and tuning their behavior is therefore also
3668 done in the same way. It is done with a spanner, and the routine
3669 responsible for drawing the spanners is
3670 @code{ly:line-spanner::print}. This routine determines the
3671 exact location of the two @i{span points} and draws a line
3672 between them, in the style requested.
3674 Here is an example showing the different line styles available,
3675 and how to tune them.
3677 @lilypond[ragged-right,verbatim,quote]
3680 \once \override Glissando.style = #'dashed-line
3682 \override Glissando.style = #'dotted-line
3684 \override Glissando.style = #'zigzag
3686 \override Glissando.style = #'trill
3691 The locations of the end-points of the spanner are computed
3692 on-the-fly for every graphic object, but it is possible to
3696 @lilypond[ragged-right,verbatim,quote]
3699 \once \override Glissando.bound-details.right.Y = #-2
3704 The value for @code{Y} is set to @w{@code{-2}} for the right end
3705 point. The left side may be similarly adjusted by specifying
3706 @code{left} instead of @code{right}.
3708 If @code{Y} is not set, the value is computed from the vertical
3709 position of the left and right attachment points of the spanner.
3711 Other adjustments of spanners are possible, for details, see
3714 @node Rotating objects
3715 @subsection Rotating objects
3717 Both layout objects and elements of markup text can be rotated by
3718 any angle about any point, but the method of doing so differs.
3721 * Rotating layout objects::
3725 @node Rotating layout objects
3726 @unnumberedsubsubsec Rotating layout objects
3728 @cindex rotating objects
3729 @cindex objects, rotating
3731 All layout objects which support the @code{grob-interface} can be
3732 rotated by setting their @code{rotation} property. This takes a
3733 list of three items: the angle of rotation counter-clockwise,
3734 and the x and y coordinates of the point relative to the object's
3735 reference point about which the rotation is to be performed. The
3736 angle of rotation is specified in degrees and the coordinates in
3739 The angle of rotation and the coordinates of the rotation point must
3740 be determined by trial and error.
3742 @cindex hairpins, angled
3743 @cindex angled hairpins
3745 There are only a few situations where the rotation of layout
3746 objects is useful; the following example shows one situation where
3749 @lilypond[quote,fragment,verbatim]
3751 \override Hairpin.rotation = #'(20 -1 0)
3755 @node Rotating markup
3756 @unnumberedsubsubsec Rotating markup
3758 All markup text can be rotated to lie at any angle by prefixing it
3759 with the @code{\rotate} command. The command takes two arguments:
3760 the angle of rotation in degrees counter-clockwise and the text to
3761 be rotated. The extents of the text are not rotated: they take
3762 their values from the extremes of the x and y coordinates of the
3763 rotated text. In the following example the
3764 @code{outside-staff-priority} property for text is set to @code{#f}
3765 to disable the automatic collision avoidance, which would push some
3766 of the text too high.
3768 @lilypond[quote,fragment,verbatim]
3769 \override TextScript.outside-staff-priority = ##f
3770 g4^\markup { \rotate #30 "a G" }
3771 b^\markup { \rotate #30 "a B" }
3772 des'^\markup { \rotate #30 "a D-Flat" }
3773 fis'^\markup { \rotate #30 "an F-Sharp" }
3776 @node Advanced tweaks
3777 @section Advanced tweaks
3779 This section discusses various approaches to fine tuning the
3780 appearance of the printed score.
3783 * Aligning objects::
3784 * Vertical grouping of grobs::
3785 * Modifying stencils::
3786 * Modifying shapes::
3787 * Modifying broken spanners::
3788 * Unpure-pure containers::
3793 @rlearning{Tweaking output},
3794 @rlearning{Other sources of information}.
3797 @ref{Explaining the Internals Reference},
3798 @ref{Modifying properties}.
3801 @rextend{Interfaces for programmers}.
3804 @file{scm/define-grobs.scm}.
3807 @rlsr{Tweaks and overrides}.
3809 Internals Reference:
3810 @rinternals{All layout objects}.
3813 @node Aligning objects
3814 @subsection Aligning objects
3816 Graphical objects which support the @code{self-alignment-interface}
3817 and/or the @code{side-position-interface} can be aligned to a previously
3818 placed object in a variety of ways. For a list of these objects, see
3819 @rinternals{self-alignment-interface} and @rinternals{side-position-interface}.
3821 All graphical objects have a reference point, a horizontal extent and a
3822 vertical extent. The horizontal extent is a pair of numbers
3823 giving the displacements from the reference point of the left and
3824 right edges, displacements to the left being negative. The vertical
3825 extent is a pair of numbers giving the displacement from the reference
3826 point to the bottom and top edges, displacements down being negative.
3828 An object's position on a staff is given by the values of the
3829 @code{X-offset} and @code{Y-offset} properties. The value of
3830 @code{X-offset} gives the displacement from the X coordinate of
3831 the reference point of the parent object, and the value of
3832 @code{Y-offset} gives the displacement from the center line of the
3833 staff. The values of @code{X-offset} and @code{Y-offset} may
3834 be set directly or may be set to be calculated by procedures in order
3835 to achieve alignment with the parent object.
3837 @warning{Many objects have special positioning considerations which
3838 cause any setting of @code{X-offset} or @code{Y-offset} to be
3839 ignored or modified, even though the object supports the
3840 @code{self-alignment-interface}. Overriding the @code{X-offset}
3841 or @code{Y-offset} properties to a fixed value causes the respective
3842 @code{self-alignment} property to be disregarded.}
3844 For example, an accidental can be repositioned vertically by setting
3845 @code{Y-offset} but any changes to @code{X-offset} have no effect.
3847 Rehearsal marks may be aligned with breakable objects such as bar
3848 lines, clef symbols, time signature symbols and key signatures. There
3849 are special properties to be found in the @code{break-aligned-interface}
3850 for positioning rehearsal marks on such objects.
3854 @ref{Using the break-alignable-interface}.
3857 @rextend{Callback functions}.
3860 * Setting X-offset and Y-offset directly::
3861 * Using the side-position-interface::
3862 * Using the self-alignment-interface::
3863 * Using the break-alignable-interface::
3866 @node Setting X-offset and Y-offset directly
3867 @unnumberedsubsubsec Setting @code{X-offset} and @code{Y-offset} directly
3869 Numerical values may be given to the @code{X-offset} and @code{Y-offset}
3870 properties of many objects. The following example shows three
3871 notes with the default fingering position and the positions with @code{X-offset}
3872 and @code{Y-offset} modified.
3874 @lilypond[verbatim,fragment,quote]
3881 -\tweak X-offset #-1
3888 @node Using the side-position-interface
3889 @unnumberedsubsubsec Using the @code{side-position-interface}
3891 An object which supports the @code{side-position-interface} can be
3892 placed next to its parent object so that
3893 the specified edges of the two objects touch. The object may be
3894 placed above, below, to the right or to the left of the parent.
3895 The parent cannot be specified; it is determined by the order of
3896 elements in the input stream. Most objects have the associated
3897 note head as their parent.
3899 The values of the @code{side-axis} and @code{direction} properties
3900 determine where the object is to be placed, as follows:
3902 @c TODO add an example of each to the table
3904 @multitable @columnfractions .3 .3 .3
3905 @headitem @code{side-axis} @tab @code{direction} @tab
3906 @headitem property @tab property @tab Placement
3908 @item @code{0} @tab @code{-1} @tab left
3909 @item @code{0} @tab @code{1} @tab right
3910 @item @code{1} @tab @code{-1} @tab below
3911 @item @code{1} @tab @code{1} @tab above
3915 When @code{side-axis} is @code{0}, @code{X-offset} should be set to
3916 the procedure @code{ly:side-position-interface::x-aligned-side}.
3917 This procedure will return the correct value of @code{X-offset} to
3918 place the object to the left or right side of the parent according
3919 to value of @code{direction}.
3921 When @code{side-axis} is @code{1}, @code{Y-offset} should be set to
3922 the procedure @code{ly:side-position-interface::y-aligned-side}.
3923 This procedure will return the correct value of @code{Y-offset} to
3924 place the object to the top or bottom of the parent according
3925 to value of @code{direction}.
3927 @c TODO Add examples
3929 @node Using the self-alignment-interface
3930 @unnumberedsubsubsec Using the @code{self-alignment-interface}
3932 @subsubsubheading Self-aligning objects horizontally
3934 The horizontal alignment of an object which supports the
3935 @code{self-alignment-interface} is controlled by the value of
3936 the @code{self-alignment-X} property, provided the object's
3937 @code{X-offset} property is set to
3938 @code{ly:self-alignment-interface::x-aligned-on-self}.
3939 @code{self-alignment-X} may be given any
3940 real value, in units of half the total X extent of the
3941 object. Negative values move the object to the right, positive
3942 to the left. A value of @code{0} centers the object on the
3943 reference point of its parent, a value of @w{@code{-1}} aligns the
3944 left edge of the object on the reference point of its parent,
3945 and a value of @code{1} aligns the right edge of the object on the
3946 reference point of its parent. The symbols @code{LEFT},
3947 @code{CENTER}, and @code{RIGHT} may be used instead of the values
3948 @w{@code{-1}}, @code{0}, and @code{1}, respectively.
3950 Normally the @code{\override} command would be used to modify the
3951 value of @code{self-alignment-X}, but the @code{\tweak} command
3952 can be used to separately align several annotations on a single
3955 @lilypond[quote,verbatim,fragment]
3957 -\tweak self-alignment-X #-1
3959 -\tweak self-alignment-X #0
3961 -\tweak self-alignment-X #RIGHT
3963 -\tweak self-alignment-X #-2.5
3964 ^"aligned further to the right"
3967 @subsubsubheading Self-aligning objects vertically
3969 Objects may be aligned vertically in an analogous way to aligning
3970 them horizontally if the @code{Y-offset} property is set to
3971 @code{ly:self-alignment-interface::y-aligned-on-self}. However,
3972 other mechanisms are often involved in vertical alignment: the
3973 value of @code{Y-offset} is just one variable taken into account.
3974 This may make adjusting the value of some objects tricky.
3975 The units are just half the vertical extent of the object, which
3976 is usually quite small, so quite large numbers may be required.
3977 A value of @w{@code{-1}} aligns the lower edge of the object with
3978 the reference point of the parent object, a value of @code{0}
3979 aligns the center of the object with the reference point of the
3980 parent, and a value of @code{1} aligns the top edge of the object
3981 with the reference point of the parent. The symbols @code{DOWN},
3982 @code{CENTER}, and @code{UP} may be substituted for @w{@code{-1}},
3983 @code{0}, and @code{1}, respectively.
3985 @subsubsubheading Self-aligning objects in both directions
3987 By setting both @code{X-offset} and @code{Y-offset}, an object may
3988 be aligned in both directions simultaneously.
3990 The following example shows how to adjust a fingering mark so
3991 that it nestles close to the note head.
3993 @lilypond[quote,verbatim,fragment]
3995 -\tweak self-alignment-X #0.5 % move horizontally left
3996 -\tweak Y-offset #ly:self-alignment-interface::y-aligned-on-self
3997 -\tweak self-alignment-Y #-1 % move vertically up
4002 @unnumberedsubsubsec Using the @code{aligned-on-parent} procedures
4004 @c Cannot document as they do not seem to operate consistently on all objects -td
4005 @c TODO investigate further
4007 The @code{aligned-on-parent} procedures are used in the same way
4008 as the @code{aligned-on-self} procedures, they difference being
4009 that they permit an object to be aligned with the @emph{edges} of
4010 the parent rather than the parent's reference point. The following
4011 example shows the difference:
4015 @lilypond[verbatim,quote]
4021 @unnumberedsubsubsec Using the @code{centered-on-parent} procedures
4023 @c Cannot document as they do not seem to operate consistently on all objects -td
4024 @c TODO investigate further
4028 @c TODO The align-interface, BassFigureAlignment and VerticalAlignment
4030 @node Using the break-alignable-interface
4031 @unnumberedsubsubsec Using the @code{break-alignable-interface}
4033 @cindex align to objects
4034 @cindex break-align-symbols
4036 Rehearsal marks and bar numbers may be aligned with notation
4037 objects other than bar lines. These objects include @code{ambitus},
4038 @code{breathing-sign}, @code{clef}, @code{custos}, @code{staff-bar},
4039 @code{left-edge}, @code{key-cancellation}, @code{key-signature}, and
4040 @code{time-signature}.
4042 Each type of object has its own default reference point, to which
4043 rehearsal marks are aligned:
4045 @lilypond[verbatim,quote,fragment]
4046 % The rehearsal mark will be aligned to the right edge of the Clef
4047 \override Score.RehearsalMark.break-align-symbols = #'(clef)
4052 % The rehearsal mark will be aligned to the left edge of the Time Signature
4053 \override Score.RehearsalMark.break-align-symbols = #'(time-signature)
4059 % The rehearsal mark will be centered above the Breath Mark
4060 \override Score.RehearsalMark.break-align-symbols = #'(breathing-sign)
4069 A list of possible target alignment objects may be specified. If
4070 some of the objects are invisible at that point due to the setting
4071 of @code{break-visibility} or the explicit visibility settings for
4072 keys and clefs, the rehearsal mark or bar number is aligned to the
4073 first object in the list which is visible. If no objects in the
4074 list are visible the object is aligned to the bar line. If the bar
4075 line is invisible the object is aligned to the place where the bar
4078 @lilypond[verbatim,quote,fragment]
4079 % The rehearsal mark will be aligned to the right edge of the Key Signature
4080 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4085 % The rehearsal mark will be aligned to the right edge of the Clef
4086 \set Staff.explicitKeySignatureVisibility = #all-invisible
4087 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4092 % The rehearsal mark will be centered above the Bar Line
4093 \set Staff.explicitKeySignatureVisibility = #all-invisible
4094 \set Staff.explicitClefVisibility = #all-invisible
4095 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4102 The alignment of the rehearsal mark relative to the notation object
4103 can be changed, as shown in the following example. In a score with
4104 multiple staves, this setting should be done for all the staves.
4106 @lilypond[verbatim,quote,fragment]
4107 % The RehearsalMark will be aligned with the right edge of the Key Signature
4108 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4114 % The RehearsalMark will be centered above the Key Signature
4115 \once \override Score.KeySignature.break-align-anchor-alignment = #CENTER
4119 % The RehearsalMark will be aligned with the left edge of the Key Signature
4120 \once \override Score.KeySignature.break-align-anchor-alignment = #LEFT
4126 The rehearsal mark can also be offset to the right or left of the left
4127 edge by an arbitrary amount. The units are staff-spaces:
4129 @lilypond[verbatim,quote,fragment]
4130 % The RehearsalMark will be aligned with the left edge of the Key Signature
4131 % and then shifted right by 3.5 staff-spaces
4132 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4133 \once \override Score.KeySignature.break-align-anchor = #3.5
4137 % The RehearsalMark will be aligned with the left edge of the Key Signature
4138 % and then shifted left by 2 staff-spaces
4139 \once \override Score.KeySignature.break-align-anchor = #-2
4146 @node Vertical grouping of grobs
4147 @subsection Vertical grouping of grobs
4149 @c TODO Expand this section
4151 The VerticalAlignment and VerticalAxisGroup grobs work together.
4152 VerticalAxisGroup groups together different grobs like Staff, Lyrics,
4153 etc. VerticalAlignment then vertically aligns the different grobs
4154 grouped together by VerticalAxisGroup. There is usually only one
4155 VerticalAlignment per score but every Staff, Lyrics, etc. has its own
4159 @node Modifying stencils
4160 @subsection Modifying stencils
4162 All layout objects have a @code{stencil} property which is part of
4163 the @code{grob-interface}. By default, this property is usually
4164 set to a function specific to the object that is tailor-made to
4165 render the symbol which represents it in the output. For example,
4166 the standard setting for the @code{stencil} property of the
4167 @code{MultiMeasureRest} object is @code{ly:multi-measure-rest::print}.
4169 The standard symbol for any object can be replaced by modifying the
4170 @code{stencil} property to reference a different, specially-written,
4171 procedure. This requires a high level of knowledge of the internal
4172 workings of LilyPond, but there is an easier way which can often
4173 produce adequate results.
4175 This is to set the @code{stencil} property to the procedure which
4176 prints text -- @code{ly:text-interface::print} -- and to add a
4177 @code{text} property to the object which is set to contain the
4178 markup text which produces the required symbol. Due to the
4179 flexibility of markup, much can be achieved -- see in particular
4180 @ref{Graphic notation inside markup}.
4182 The following example demonstrates this by changing the note head
4183 symbol to a cross within a circle.
4185 @lilypond[verbatim,quote]
4187 \once \override NoteHead.stencil = #ly:text-interface::print
4188 \once \override NoteHead.text = \markup {
4190 \halign #-0.7 \draw-circle #0.85 #0.2 ##f
4191 \musicglyph #"noteheads.s2cross"
4199 Any of the glyphs in the Feta Font can be supplied to the
4200 @code{\musicglyph} markup command -- see @ref{The Feta font}.
4202 @file{EPS} files and Postscript commands can both be inserted inline
4203 using the @code{\epsfile} and @code{\postscript} markup commands
4204 respectively -- see @ref{Graphic}.
4209 @ref{Graphic notation inside markup},
4210 @ref{Formatting text},
4211 @ref{Text markup commands},
4212 @ref{The Feta font},
4216 @node Modifying shapes
4217 @subsection Modifying shapes
4220 * Modifying ties and slurs::
4223 @node Modifying ties and slurs
4224 @unnumberedsubsubsec Modifying ties and slurs
4226 @cindex slurs, modifying
4227 @cindex ties, modifying
4228 @cindex Bézier curves, control points
4229 @cindex control points, Bézier curves
4231 @code{Tie}s, @code{Slur}s, @code{PhrasingSlur}s,
4232 @code{LaissezVibrerTie}s and @code{RepeatTie}s are all drawn as
4233 third-order Bézier curves. If the shape of the tie or slur which
4234 is calculated automatically is not optimum, the shape may be
4235 modified manually in two ways:
4239 by specifying the displacements to be made to the control points
4240 of the automatically calculated Bézier curve, or
4243 by explicitly specifying the positions of the four control points
4244 required to define the wanted curve.
4247 Both methods are explained below. The first method is more suitable
4248 if only slight adjustments to the curve are required; the second may
4249 be better for creating curves which are related to just a single
4252 @subsubsubheading Cubic Bézier curves
4254 Third-order or cubic Bézier curves are defined by four control
4255 points. The first and fourth control points are precisely the
4256 starting and ending points of the curve. The intermediate two
4257 control points define the shape. Animations showing how the curve
4258 is drawn can be found on the web, but the following description
4259 may be helpful. The curve starts from the first control point
4260 heading directly towards the second, gradually bending over to
4261 head towards the third and continuing to bend over to head towards
4262 the fourth, arriving there travelling directly from the third
4263 control point. The curve is entirely contained in the
4264 quadrilateral defined by the four control points. Translations,
4265 rotations and scaling of the control points all result in exactly
4266 the same operations on the curve.
4268 @subsubsubheading Specifying displacements from current control points
4270 @cindex shaping slurs and ties
4273 In this example the automatic placement of the tie is not optimum,
4274 and @code{\tieDown} would not help.
4276 @lilypond[verbatim,quote]
4280 \relative { r4 <g' c,> <g c,> <g c,> }
4284 Adjusting the control points of the tie with @code{\shape} allows
4285 the collisions to be avoided.
4287 The syntax of @code{\shape} is
4290 [-]@code{\shape} @var{displacements} @var{item}
4293 This will reposition the control-points of @var{item} by the amounts
4294 given by @var{displacements}. The @var{displacements} argument is a
4295 list of number pairs or a list of such lists. Each element of a pair
4296 represents the displacement of one of the coordinates of a
4297 control-point. If @var{item} is a string, the result is
4298 @code{\once\override} for the specified grob type. If @var{item} is
4299 a music expression, the result is the same music expression with an
4300 appropriate tweak applied.
4302 In other words, the @code{\shape} function can act as either a
4303 @code{\once\override} command or a @code{\tweak} command depending
4304 on whether the @var{item} argument is a grob name, like @qq{Slur},
4305 or a music expression, like @qq{(}. The @var{displacements} argument
4306 specifies the displacements of the four control points as a list of
4307 four pairs of (dx . dy) values in units of staff-spaces (or a list
4308 of such lists if the curve has more than one segment).
4310 The leading hyphen is required if and only if the @code{\tweak} form
4313 So, using the same example as above and the @code{\once\override}
4314 form of @code{\shape}, this will raise the tie by half a staff-space:
4316 @lilypond[verbatim,quote]
4319 \shape #'((0 . 0.5) (0 . 0.5) (0 . 0.5) (0 . 0.5)) Tie
4323 \relative { r4 <g' c,> <g c,> <g c,> }
4327 This positioning of the tie is better, but maybe it should be raised
4328 more in the center. The following example does this, this time using
4329 the alternative @code{\tweak} form:
4331 @lilypond[verbatim,quote]
4334 e'1-\shape #'((0 . 0.5) (0 . 1) (0 . 1) (0 . 0.5)) ~ e'
4337 \relative { r4 <g' c,> <g c,> <g c,> }
4341 Changes to the horizontal positions of the control points may be made
4342 in the same way, and two different curves starting at the same
4343 musical moment may also be shaped:
4345 @lilypond[verbatim,quote,ragged-right]
4347 c''8(\( a) a'4 e c\)
4348 \shape #'((0.7 . -0.4) (0.5 . -0.4) (0.3 . -0.3) (0 . -0.2)) Slur
4349 \shape #'((0 . 0) (0 . 0.5) (0 . 0.5) (0 . 0)) PhrasingSlur
4354 The @code{\shape} function can also displace the control points of
4355 curves which stretch across line breaks. Each piece of the broken
4356 curve can be given its own list of offsets. If changes to a
4357 particular segment are not needed, the empty list can serve as a
4358 placeholder. In this example the line break makes the single slur
4361 @lilypond[verbatim,quote,ragged-right]
4369 Changing the shapes of the two halves of the slur makes it clearer
4370 that the slur continues over the line break:
4372 @lilypond[verbatim,quote,ragged-right]
4373 % () may be used as a shorthand for ((0 . 0) (0 . 0) (0 . 0) (0 . 0))
4374 % if any of the segments does not need to be changed
4377 (( 0 . 0) (0 . 0) (0 . 0) (0 . 1))
4378 ((0.5 . 1.5) (1 . 0) (0 . 0) (0 . -1.5))
4386 If an S-shaped curve is required the control points must always be
4387 adjusted manually --- LilyPond will never select such shapes
4390 @lilypond[verbatim,quote]
4392 c8( e b-> f d' a e-> g)
4393 \shape #'((0 . -1) (5.5 . -0.5) (-5.5 . -10.5) (0 . -5.5)) PhrasingSlur
4394 c8\( e b-> f d' a e-> g\)
4398 @subsubsubheading Specifying control points explicitly
4400 The coordinates of the Bézier control points are specified in units
4401 of staff-spaces. The X@tie{}coordinate is relative to the reference
4402 point of the note to which the tie or slur is attached, and the
4403 Y@tie{}coordinate is relative to the staff center line. The
4404 coordinates are specified as a list of four pairs of decimal numbers
4405 (reals). One approach is to estimate the coordinates of the two
4406 end points, and then guess the two intermediate points. The optimum
4407 values are then found by trial and error. Be aware that these values
4408 may need to be manually adjusted if any further changes are made to
4409 the music or the layout.
4411 One situation where specifying the control points explicitly is
4412 preferable to specifying displacements is when they need to be
4413 specified relative to a single note. Here is an example of this.
4414 It shows one way of indicating a slur extending into alternative
4415 sections of a volta repeat.
4417 @lilypond[verbatim,quote]
4420 \repeat volta 3 { c4 d( e f }
4425 % create a slur and move it to a new position
4426 % the <> is just an empty chord to carry the slur termination
4427 -\tweak control-points #'((-2 . 3.8) (-1 . 3.9) (0 . 4) (1 . 3.4)) ( <> )
4432 % create a slur and move it to a new position
4433 -\tweak control-points #'((-2 . 3) (-1 . 3.1) (0 . 3.2) (1 . 2.4)) ( <> )
4441 It is not possible to modify shapes of ties or slurs by changing
4442 the @code{control-points} property if there are multiple ties or slurs
4443 at the same musical moment -- the @code{\tweak} command will also not
4444 work in this case. However, the @code{tie-configuration} property of
4445 @code{TieColumn} can be overridden to set start line and direction as
4449 Internals Reference:
4450 @rinternals{TieColumn}.
4453 @node Modifying broken spanners
4454 @subsection Modifying broken spanners
4457 * Using alterBroken::
4460 @node Using alterBroken
4461 @unnumberedsubsubsec Using @code{\alterBroken}
4463 @cindex spanners, modifying
4464 @cindex broken spanners, modifying
4465 @funindex \alterBroken
4467 When a spanner crosses a line break or breaks, each piece
4468 inherits the attributes of the original spanner. Thus, ordinary
4469 tweaking of a broken spanner applies the same modifications to
4470 each of its segments. In the example below, overriding
4471 @code{thickness} affects the slur on either side of the line
4474 @lilypond[verbatim,quote,ragged-right]
4477 \once\override Slur.thickness = 10
4484 Independently modifying the appearance of individual pieces
4485 of a broken spanner is possible with the @code{\alterBroken}
4486 command. This command can produce either an @code{\override}
4487 or a @code{\tweak} of a spanner property.
4489 The syntax for @code{\alterBroken} is
4492 [-]@code{\alterBroken} @var{property} @var{values} @var{item}
4495 The argument @var{values} is a list of values, one for each
4496 broken piece. If @var{item} is a grob name like @code{Slur} or
4497 @code{Staff.PianoPedalBracket}, the result is an @code{\override}
4498 of the specified grob type. If @var{item} is a music expression
4499 such as @qq{(} or @qq{[} the result is the same music expression
4500 with an appropriate tweak applied.
4502 The leading hyphen must be used with the @code{\tweak} form. Do
4503 not add it when @code{\alterBroken} is used as an
4506 In its @code{\override} usage, @code{\alterBroken} may be
4507 prefaced by @code{\once} or @code{\temporary} and reverted by
4508 using @code{\revert} with @var{property}.
4510 The following code applies an independent @code{\override} to
4511 each of the slur segments in the previous example:
4513 @lilypond[verbatim,quote,ragged-right]
4516 \alterBroken thickness #'(10 1) Slur
4523 The @code{\alterBroken} command may be used with any spanner
4524 object, including @code{Tie}, @code{PhrasingSlur}, @code{Beam}
4525 and @code{TextSpanner}. For example, an editor preparing a
4526 scholarly edition may wish to indicate the absence of part of a
4527 phrasing slur in a source by dashing only the segment which has
4528 been added. The following example illustrates how this can be
4529 done, in this case using the @code{\tweak} form of the command:
4531 @lilypond[verbatim,quote,ragged-right]
4532 % The empty list is conveniently used below, because it is the
4533 % default setting of dash-definition, resulting in a solid curve.
4535 c''2-\alterBroken dash-definition #'(() ((0 1.0 0.4 0.75))) \(e
4541 It is important to understand that @code{\alterBroken} will set
4542 each piece of a broken spanner to the corresponding value in
4543 @var{values}. When there are fewer values than pieces, any
4544 additional piece will be assigned the empty list. This may lead
4545 to undesired results if the layout property is not set to the
4546 empty list by default. In such cases, each segment should be
4547 assigned an appropriate value.
4550 Line breaks may occur in different places following changes in
4551 layout. Settings chosen for @code{\alterBroken} may be unsuitable
4552 for a spanner that is no longer broken or is split into more
4553 segments than before. Explicit use of @code{\break} can guard
4554 against this situation.
4556 The @code{\alterBroken} command is ineffective for spanner
4557 properties accessed before line-breaking such as
4562 @rextend{Difficult tweaks}.
4565 @node Unpure-pure containers
4566 @subsection Unpure-pure containers
4568 @cindex Scheme, pure containers
4569 @cindex Scheme, unpure containers
4570 @cindex pure containers, Scheme
4571 @cindex unpure containers, Scheme
4572 @cindex horizontal spacing, overriding
4574 Unpure-pure containers are useful for overriding @emph{Y-axis} spacing
4575 calculations - specifically @code{Y-offset} and @code{Y-extent} - with a
4576 Scheme function instead of a literal (i.e. a number or pair).
4578 For certain grobs, the @code{Y-extent} is based on the @code{stencil}
4579 property, overriding the stencil property of one of these will
4580 require an additional @code{Y-extent} override with an unpure-pure
4581 container. When a function overrides a @code{Y-offset} and/or
4582 @code{Y-extent} it is assumed that this will trigger line breaking
4583 calculations too early during compilation. So the function is not
4584 evaluated at all (usually returning a value of @samp{0} or
4585 @samp{'(0 . 0)}) which can result in collisions. A @q{pure} function
4586 will not affect properties, objects or grob suicides and therefore will
4587 always have its Y-axis-related evaluated correctly.
4589 Currently, there are about thirty functions that are already considered
4590 @q{pure} and Unpure-pure containers are a way to set functions not on
4591 this list as @q{pure}. The @q{pure} function is evaluated @emph{before}
4592 any line-breaking and so the horizontal spacing can be adjusted
4593 @q{in time}. The @q{unpure} function is then evaluated @emph{after}
4596 @warning{As it is difficult to always know which functions are on this
4597 list we recommend that any @q{pure} functions you create do not use
4598 @code{Beam} or @code{VerticalAlignment} grobs.}
4600 An unpure-pure container is constructed as follows;
4602 @code{(ly:make-unpure-pure-container f0 f1)}
4604 where @code{f0} is a function taking @var{n} arguments (@var{n >= 1})
4605 and the first argument must always be the grob. This is the function
4606 that gives the actual result. @var{f1} is the function being labeled
4607 as @q{pure} that takes @var{n + 2} arguments. Again, the first argument
4608 must always still be the grob but the second and third are @q{start}
4609 and @q{end} arguments.
4611 @var{start} and @var{end} are, for all intents and purposes, dummy
4612 values that only matter for @code{Spanners} (i.e @code{Hairpin} or
4613 @code{Beam}), that can return different height estimations based on a
4614 starting and ending column.
4616 The rest are the other arguments to the first function (which
4617 may be none if @var{n = 1}).
4619 The results of the second function are used as an approximation of the
4620 value needed which is then used by the first function to get the real
4621 value which is then used for fine-tuning much later during the spacing
4624 @c TODO: The following example supposedly showing a collision no longer
4625 @c 'works' since 2.18.x. Another example of a collision is needed.
4628 @lilypond[verbatim,quote,ragged-right]
4629 #(define (square-line-circle-space grob)
4630 (let* ((pitch (ly:event-property (ly:grob-property grob 'cause) 'pitch))
4631 (notename (ly:pitch-notename pitch)))
4632 (if (= 0 (modulo notename 2))
4633 (make-circle-stencil 0.5 0.0 #t)
4634 (make-filled-box-stencil '(0 . 1.0)
4637 squareLineCircleSpace = {
4638 \override NoteHead.stencil = #square-line-circle-space
4641 smartSquareLineCircleSpace = {
4642 \squareLineCircleSpace
4643 \override NoteHead.Y-extent =
4644 #(ly:make-unpure-pure-container
4645 ly:grob::stencil-height
4646 (lambda (grob start end) (ly:grob::stencil-height grob)))
4649 \new Voice \with { \remove "Stem_engraver" }
4651 \squareLineCircleSpace
4653 \smartSquareLineCircleSpace
4658 In the first measure, without the unpure-pure container, the spacing
4659 engine does not know the width of the note head and lets it collide with
4660 the accidentals. In the second measure, with unpure-pure containers,
4661 the spacing engine knows the width of the note heads and avoids the
4662 collision by lengthening the line accordingly.
4664 Usually for simple calculations nearly-identical functions for
4665 both the @q{unpure} and @q{pure} parts can be used, by only
4666 changing the number of arguments passed to, and the scope of, the
4667 function. This use case is frequent enough that
4668 @code{ly:make-unpure-pure-container} constructs such a second
4669 function by default when called with only one function argument.
4671 @warning{If a function is labeled as @q{pure} and it turns out not to
4672 be, the results can be unexpected.}
4675 @node Using music functions
4676 @section Using music functions
4678 @c TODO -- add @seealso, etc. to these subsections
4680 Where tweaks need to be reused with different music expressions,
4681 it is often convenient to make the tweak part of a @emph{music
4682 function}. In this section, we discuss only @emph{substitution}
4683 functions, where the object is to substitute a variable into a
4684 piece of LilyPond input code. Other more complex functions are
4685 described in @rextend{Music functions}.
4688 * Substitution function syntax::
4689 * Substitution function examples::
4692 @node Substitution function syntax
4693 @subsection Substitution function syntax
4695 Making a function that substitutes a variable into LilyPond
4696 code is easy. The general form of these functions is
4700 #(define-music-function
4701 (@var{arg1} @var{arg2} @dots{})
4702 (@var{type1?} @var{type2?} @dots{})
4704 @var{@dots{}music@dots{}}
4711 @multitable @columnfractions .33 .66
4712 @item @code{@var{argN}}
4713 @tab @var{n}th argument
4715 @item @code{@var{typeN?}}
4716 @tab a scheme @emph{type predicate} for which @code{@var{argN}}
4717 must return @code{#t}.
4719 @item @code{@var{@dots{}music@dots{}}}
4720 @tab normal LilyPond input, using @code{$} (in places where only
4721 Lilypond constructs are allowed) or @code{#} (to use it as a Scheme
4722 value or music function argument or music inside of music lists) to
4727 The list of type predicates is required. Some of the most common
4728 type predicates used in music functions are:
4732 cheap-list? @emph{(use instead of }@q{list?}@emph{ for faster processing)}
4744 For a list of available type predicates, see
4745 @ref{Predefined type predicates}. User-defined type predicates
4750 @ref{Predefined type predicates}.
4753 @rextend{Music functions}.
4756 @file{lily/music-scheme.cc},
4758 @file{scm/lily.scm}.
4761 @node Substitution function examples
4762 @subsection Substitution function examples
4764 This section introduces some substitution function examples.
4765 These are not intended to be exhaustive, but rather to demonstrate
4766 some of the possibilities of simple substitution functions.
4768 In the first example, a function is defined that simplifies
4769 setting the padding of a TextScript:
4771 @lilypond[quote,verbatim,ragged-right]
4773 #(define-music-function
4777 \once \override TextScript.padding = #padding
4781 c''4^"piu mosso" b a b
4783 c4^"piu mosso" b a b
4785 c4^"piu mosso" b a b
4789 In addition to numbers, we can use music expressions such
4790 as notes for arguments to music functions:
4792 @lilypond[quote,verbatim,ragged-right]
4794 #(define-music-function
4798 \tweak NoteHead.stencil #ly:text-interface::print
4799 \tweak NoteHead.text
4800 \markup \musicglyph #"custodes.mensural.u0"
4801 \tweak Stem.stencil ##f
4805 \relative { c'4 d e f \custosNote g }
4809 Both of those functions are simple single expressions where only
4810 the last element of a function call or override is missing. For
4811 those particular function definitions, there is a simpler
4812 alternative syntax, namely just writing out the constant part of
4813 the expression and replacing its final missing element with
4816 @lilypond[quote,verbatim,ragged-right]
4818 \once \override TextScript.padding = \etc
4821 c''4^"piu mosso" b a b
4823 c4^"piu mosso" b a b
4825 c4^"piu mosso" b a b
4829 @lilypond[quote,verbatim,ragged-right]
4831 \tweak NoteHead.stencil #ly:text-interface::print
4832 \tweak NoteHead.text
4833 \markup \musicglyph #"custodes.mensural.u0"
4834 \tweak Stem.stencil ##f
4837 \relative { c'4 d e f \custosNote g }
4841 Substitution functions with multiple arguments can be defined:
4843 @lilypond[quote,verbatim,ragged-right]
4845 #(define-music-function
4849 \once \override Score.MetronomeMark.padding = #padding
4850 \tempo \markup { \bold #tempotext }
4854 \tempo \markup { "Low tempo" }
4856 \tempoPadded #4.0 "High tempo"
4861 @c TODO: add appropriate @@ref's here.