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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
1134 Specific contexts, like @code{Staff} and @code{Voice}, are made from
1135 simple building blocks. It is possible to create new types of
1136 contexts with different combinations of engraver plug-ins.
1138 The next example shows how to build a different type of
1139 @code{Voice} context from scratch. It will be similar to
1140 @code{Voice}, but only prints centered slash note heads. It can be used
1141 to indicate improvisation in jazz pieces,
1143 @lilypond[quote,ragged-right]
1144 \layout { \context {
1146 \type "Engraver_group"
1147 \consists "Note_heads_engraver"
1148 \consists "Rhythmic_column_engraver"
1149 \consists "Text_engraver"
1150 \consists "Pitch_squash_engraver"
1151 squashedPosition = #0
1152 \override NoteHead.style = #'slash
1157 \accepts "ImproVoice"
1161 a'4 d8 bes8 \new ImproVoice { c4^"ad lib" c
1162 c4 c^"undress" c_"while playing :)" c }
1168 These settings are defined within a @code{\context} block inside a
1169 @code{\layout} block,
1179 In the following discussion, the example input shown should go in place
1180 of the @dots{} in the previous fragment.
1182 First it is necessary to define a name for the new context:
1188 Since it is similar to the @code{Voice} context, we want commands that
1189 work in (existing) @code{Voice} contexts to continue working. This is
1190 achieved by giving the new context an alias of @code{Voice},
1196 The context will print notes and instructive texts, so we need to add
1197 the engravers which provide this functionality, plus the engraver which
1198 groups notes, stems and rests which occur at the same musical moment
1202 \consists "Note_heads_engraver"
1203 \consists "Text_engraver"
1204 \consists "Rhythmic_column_engraver"
1207 The note heads should all be placed on the center line,
1210 \consists "Pitch_squash_engraver"
1211 squashedPosition = #0
1214 The @code{Pitch_squash_engraver} modifies note heads (created
1215 by the @code{Note_heads_engraver}) and sets their vertical
1216 position to the value of @code{squashedPosition}, in this
1217 case@tie{}@code{0}, the center line.
1219 The notes look like a slash, and have no stem,
1222 \override NoteHead.style = #'slash
1226 All these plug-ins have to communicate under the control of the
1227 context. The mechanisms with which contexts communicate are
1228 established by declaring the context @code{\type}. Within a
1229 @code{\layout} block, most contexts will be of type
1230 @code{Engraver_group}. Some special contexts and contexts in
1231 @code{\midi} blocks use other context types. Copying and
1232 modifying an existing context definition will also fill in the
1233 type. Since this example creates a definition from scratch, it
1234 needs to be specified explicitly.
1237 \type "Engraver_group"
1240 Put together, we get
1245 \type "Engraver_group"
1246 \consists "Note_heads_engraver"
1247 \consists "Text_engraver"
1248 \consists "Rhythmic_column_engraver"
1249 \consists "Pitch_squash_engraver"
1250 squashedPosition = #0
1251 \override NoteHead.style = #'slash
1258 Contexts form hierarchies. We want to place the @code{ImproVoice}
1259 context within the @code{Staff} context, just like normal @code{Voice}
1260 contexts. Therefore, we modify the @code{Staff} definition with the
1261 @code{\accepts} command,
1270 @funindex \inherit-acceptability
1271 Often when reusing an existing context definition, the resulting
1272 context can be used anywhere where the original context would have
1278 \inherit-acceptability @var{to} @var{from}
1283 will arrange to have contexts of type @var{to} accepted by all
1284 contexts also accepting @var{from}. For example, using
1289 \inherit-acceptability "ImproVoice" "Voice"
1294 will add an @code{\accepts} for @code{ImproVoice} to both
1295 @code{Staff} and @code{RhythmicStaff} definitions.
1298 The opposite of @code{\accepts} is @code{\denies},
1299 which is sometimes needed when reusing existing context definitions.
1301 Arranging the required pieces into a @code{\layout} block leaves
1310 \inherit-acceptability "ImproVoice" "Voice"
1314 Then the output at the start of this subsection can be entered as
1322 c c_"while playing :)"
1328 To complete this example, changes affecting the context hierarchy
1329 should be repeated in a @code{\midi} block so that Midi output
1330 depends on the same context relations.
1334 Internals Reference:
1335 @rinternals{Note_heads_engraver},
1336 @rinternals{Text_engraver},
1337 @rinternals{Rhythmic_column_engraver},
1338 @rinternals{Pitch_squash_engraver}.
1341 @node Context layout order
1342 @subsection Context layout order
1344 @cindex contexts, layout order
1348 Contexts are normally positioned in a system from top to bottom
1349 in the order in which they are encountered in the input file. When
1350 contexts are nested, the outer context will include inner nested
1351 contexts as specified in the input file, provided the inner contexts
1352 are included in the outer context's @qq{accepts} list. Nested
1353 contexts which are not included in the outer context's @qq{accepts}
1354 list will be repositioned below the outer context rather than nested
1357 The @qq{accepts} list of a context can be changed with the
1358 @code{\accepts} or @code{\denies} commands. @code{\accepts} adds a
1359 context to the @qq{accepts} list and @code{\denies} removes a context
1362 For example, a square-braced staff group is not usually found within a
1363 curved-braced staff with connecting staff bars, and a @code{GrandStaff}
1364 does not accept a @code{StaffGroup} inside it by default.
1366 @lilypond[verbatim,quote]
1373 \new Staff { \set Staff.instrumentName = bottom f'1 }
1378 However, by using the @code{\accepts} command, @code{StaffGroup} can be
1379 added to the @code{GrandStaff} context:
1381 @lilypond[verbatim,quote]
1388 \new Staff { \set Staff.instrumentName = bottom f'1 }
1393 \accepts "StaffGroup"
1399 @code{\denies} is mainly used when a new context is being based on
1400 another, but the required nesting differs. For example, the
1401 @code{VaticanaStaff} context is based on the @code{Staff} context, but
1402 with the @code{VaticanaVoice} context substituted for the @code{Voice}
1403 context in the @qq{accepts} list.
1405 @cindex contexts, implicit
1406 @cindex implicit contexts
1407 @funindex \defaultchild
1409 Note that a context will be silently created implicitly if a
1410 command is encountered when there is no suitable context available
1413 Within a context definition, the type of subcontext to be
1414 implicitly created is specified using @code{\defaultchild}. A
1415 number of music events require a @samp{Bottom} context: when such
1416 an event is encountered, subcontexts are created recursively until
1417 reaching a context with no @samp{defaultchild} setting.
1419 Implicit context creation can at times give rise to unexpected new
1420 staves or scores. Using @code{\new} to create contexts explicitly
1421 avoids those problems.
1423 @cindex alignAboveContext
1424 @cindex alignBelowContext
1425 @funindex alignAboveContext
1426 @funindex alignBelowContext
1428 Sometimes a context is required to exist for just a brief period, a
1429 good example being the staff context for an ossia. This is usually
1430 achieved by introducing the context definition at the appropriate
1431 place in parallel with corresponding section of the main music.
1432 By default, the temporary context will be placed below all the
1433 existing contexts. To reposition it above the context called
1434 @qq{main}, it should be defined like this:
1437 \new Staff \with @{ alignAboveContext = #"main" @}
1440 A similar situation arises when positioning a temporary lyrics
1441 context within a multi-staved layout such as a @code{ChoirStaff},
1442 for example, when adding a second verse to a repeated section.
1443 By default the temporary lyrics context will be placed beneath the
1444 lower staves. By defining the temporary lyrics context with
1445 @code{alignBelowContext} it can be positioned correctly beneath
1446 the (named) lyrics context containing the first verse.
1448 Examples showing this repositioning of temporary contexts can be
1449 found elsewhere --- see @rlearning{Nesting music expressions},
1450 @ref{Modifying single staves} and @ref{Techniques specific to lyrics}.
1454 @rlearning{Nesting music expressions}.
1457 @ref{Modifying single staves},
1458 @ref{Techniques specific to lyrics}.
1461 @rprogram{An extra staff appears}.
1464 @file{ly/engraver-init.ly}.
1467 @node Explaining the Internals Reference
1468 @section Explaining the Internals Reference
1471 * Navigating the program reference::
1472 * Layout interfaces::
1473 * Determining the grob property::
1474 * Naming conventions::
1477 @node Navigating the program reference
1478 @subsection Navigating the program reference
1480 @c TODO remove this (it's in the LM)
1481 @c Replace with more factual directions
1483 Suppose we want to move the fingering indication in the fragment
1486 @lilypond[quote,fragment,verbatim]
1490 If you visit the documentation on fingering instructions (in
1491 @ref{Fingering instructions}), you will notice:
1496 Internals Reference: @rinternals{Fingering}.
1501 @c outdated info; probably will delete.
1503 This fragment points to two parts of the program reference: a page
1504 on @code{FingeringEvent} and one on @code{Fingering}.
1506 The page on @code{FingeringEvent} describes the properties of the music
1507 expression for the input @w{@code{-2}}. The page contains many links
1508 forward. For example, it says
1511 Accepted by: @rinternals{Fingering_engraver},
1515 That link brings us to the documentation for the Engraver, the
1519 This engraver creates the following layout objects: @rinternals{Fingering}.
1522 In other words, once the @code{FingeringEvent}s are interpreted, the
1523 @code{Fingering_engraver} plug-in will process them.
1527 @c I can't figure out what this is supposed to mean. -gp
1529 The @code{Fingering_engraver} is also listed to create
1530 @rinternals{Fingering} objects,
1532 @c old info? it doesn't make any sense to me with our current docs.
1534 second bit of information listed under @b{See also} in the Notation
1539 The programmer's reference is available as an HTML document. It is
1540 highly recommended that you read it in HTML form, either online or
1541 by downloading the HTML documentation. This section will be much more
1542 difficult to understand if you are using the
1546 Follow the link to @rinternals{Fingering}. At the top of the
1550 Fingering objects are created by: @rinternals{Fingering_engraver} and
1551 @rinternals{New_fingering_engraver}.
1554 By following related links inside the program reference, we can follow the
1555 flow of information within the program:
1559 @item @rinternals{Fingering}:
1560 @rinternals{Fingering} objects are created by:
1561 @rinternals{Fingering_engraver}
1563 @item @rinternals{Fingering_engraver}:
1564 Music types accepted: @rinternals{fingering-event}
1566 @item @rinternals{fingering-event}:
1567 Music event type @code{fingering-event} is in Music expressions named
1568 @rinternals{FingeringEvent}
1571 This path goes against the flow of information in the program: it
1572 starts from the output, and ends at the input event. You could
1573 also start at an input event, and read with the flow of
1574 information, eventually ending up at the output object(s).
1576 The program reference can also be browsed like a normal document. It
1577 contains chapters on
1579 @rinternals{Music definitions},
1582 @code{Music definitions}
1584 on @rinternals{Translation}, and the @rinternals{Backend}. Every
1585 chapter lists all the definitions used and all properties that may be
1589 @node Layout interfaces
1590 @subsection Layout interfaces
1592 @cindex interface, layout
1593 @cindex layout interface
1596 The HTML page that we found in the previous section describes the
1597 layout object called @rinternals{Fingering}. Such an object is a
1598 symbol within the score. It has properties that store numbers (like
1599 thicknesses and directions), but also pointers to related objects. A
1600 layout object is also called a @emph{Grob}, which is short for Graphical
1601 Object. For more details about Grobs, see @rinternals{grob-interface}.
1603 The page for @code{Fingering} lists the definitions for the
1604 @code{Fingering} object. For example, the page says
1607 @code{padding} (dimension, in staff space):
1613 which means that the number will be kept at a distance of at least 0.5
1617 Each layout object may have several functions as a notational or
1618 typographical element. For example, the Fingering object
1619 has the following aspects
1623 Its size is independent of the horizontal spacing, unlike slurs or beams.
1626 It is a piece of text. Granted, it is usually a very short text.
1629 That piece of text is typeset with a font, unlike slurs or beams.
1632 Horizontally, the center of the symbol should be aligned to the
1633 center of the note head.
1636 Vertically, the symbol is placed next to the note and the staff.
1639 The vertical position is also coordinated with other superscript
1640 and subscript symbols.
1643 Each of these aspects is captured in so-called @emph{interface}s,
1644 which are listed on the @rinternals{Fingering} page at the bottom
1647 This object supports the following interfaces:
1648 @rinternals{item-interface},
1649 @rinternals{self-alignment-interface},
1650 @rinternals{side-position-interface}, @rinternals{text-interface},
1651 @rinternals{text-script-interface}, @rinternals{font-interface},
1652 @rinternals{finger-interface}, and @rinternals{grob-interface}.
1655 Clicking any of the links will take you to the page of the respective
1656 object interface. Each interface has a number of properties. Some of
1657 them are not user-serviceable (@q{Internal properties}), but others
1660 We have been talking of @emph{the} @code{Fingering} object, but actually it
1661 does not amount to much. The initialization file (see
1662 @rlearning{Other sources of information})
1663 @file{scm/define-grobs.scm} shows the soul of the @q{object},
1668 (avoid-slur . around)
1669 (slur-padding . 0.2)
1670 (staff-padding . 0.5)
1671 (self-alignment-X . 0)
1672 (self-alignment-Y . 0)
1673 (script-priority . 100)
1674 (stencil . ,ly:text-interface::print)
1675 (direction . ,ly:script-interface::calc-direction)
1676 (font-encoding . fetaText)
1677 (font-size . -5) ; don't overlap when next to heads.
1678 (meta . ((class . Item)
1679 (interfaces . (finger-interface
1681 text-script-interface
1683 side-position-interface
1684 self-alignment-interface
1685 item-interface))))))
1689 As you can see, the @code{Fingering} object is nothing more than a
1690 bunch of variable settings, and the webpage in the Internals Reference
1691 is directly generated from this definition.
1694 @node Determining the grob property
1695 @subsection Determining the grob property
1697 @c TODO remove this (it's in the LM)
1698 @c Replace with more factual directions
1700 Recall that we wanted to change the position of the @b{2} in
1702 @lilypond[quote,fragment,verbatim]
1706 Since the @b{2} is vertically positioned next to its note, we have to
1707 meddle with the interface associated with this positioning. This is
1708 done using @code{side-position-interface}. The page for this interface
1712 @code{side-position-interface}
1714 Position a victim object (this one) next to other objects (the
1715 support). The property @code{direction} signifies where to put the
1716 victim object relative to the support (left or right, up or down?)
1721 Below this description, the variable @code{padding} is described as
1726 (dimension, in staff space)
1728 Add this much extra space between objects that are next to each other.
1732 By increasing the value of @code{padding}, we can move the fingering
1733 away from the note head. The following command will insert @qq{three
1734 staff spaces} worth of distance between the note and a fingering mark:
1737 \once \override Voice.Fingering.padding = #3
1740 Inserting the padding before the fingering object is created results in
1743 @lilypond[quote,fragment,verbatim]
1744 \once \override Voice.Fingering.padding = #3
1748 In this case, the context for this tweak is @code{Voice}. See
1749 @rinternals{Fingering_engraver} plug-in, which says:
1752 Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
1756 @node Naming conventions
1757 @subsection Naming conventions
1759 Another thing that is needed, is an overview of the various naming
1763 @item scheme functions: lowercase-with-hyphens (also includes one-word
1766 @item LilyPond-specific scheme functions: ly:plus-scheme-style
1768 @item music events, music classes and music properties:
1771 @item Grob interfaces: scheme-style
1773 @item backend properties: scheme-style (but X and Y!)
1775 @item contexts (and MusicExpressions and grobs): Capitalized or
1778 @item context properties: lowercaseFollowedByCamelCase
1780 @item engravers: Capitalized_followed_by_lowercase_and_with_underscores
1783 Questions to be answered:
1786 @item Which of these are conventions and which are rules?
1788 @item Which are rules of the underlying language, and which are
1792 @node Modifying properties
1793 @section Modifying properties
1795 @c TODO change the menu and subsection node names to use
1796 @c backslash once the new macro to handle the refs
1797 @c is available. Need to find and change all refs at
1798 @c the same time. -td
1801 * Overview of modifying properties::
1803 * The override command::
1804 * The tweak command::
1805 * set versus override::
1806 * Modifying alists::
1810 @node Overview of modifying properties
1811 @subsection Overview of modifying properties
1813 Each context is responsible for creating certain types of graphical
1814 objects. The settings used for printing these objects are also stored by
1815 context. By changing these settings, the appearance of objects can be
1818 There are two different kinds of properties stored in contexts:
1819 context properties and grob properties. Context properties are
1820 properties that apply to the context as a whole and control
1821 how the context itself is displayed. In contrast, grob properties
1822 apply to specific grob types that will be displayed in the context.
1824 The @code{\set} and @code{\unset} commands are used to change values
1825 for context properties. The @code{\override} and @code{\revert}
1826 commands are used to change values for grob properties.
1829 The syntax for this is
1832 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1835 Here @var{name} is the name of a graphical object, like
1836 @code{Stem} or @code{NoteHead}, and @var{property} is an internal
1837 variable of the formatting system (@q{grob property} or @q{layout
1838 property}). The latter is a symbol, so it must be quoted. The
1839 subsection @ref{Modifying properties}, explains what to fill in
1840 for @var{name}, @var{property}, and @var{value}. Here we only
1841 discuss the functionality of this command.
1846 \override Staff.Stem.thickness = #4.0
1850 makes stems thicker (the default is 1.3, with staff line thickness as a
1851 unit). Since the command specifies @code{Staff} as context, it only
1852 applies to the current staff. Other staves will keep their normal
1853 appearance. Here we see the command in action:
1855 @lilypond[quote,fragment,verbatim]
1857 \override Staff.Stem.thickness = #4.0
1863 The @code{\override} command changes the definition of the @code{Stem}
1864 within the current @code{Staff}. After the command is interpreted
1865 all stems are thickened.
1867 Analogous to @code{\set}, the @var{context} argument may be left out,
1868 causing the default context @code{Voice} to be used. Adding
1869 @code{\once} applies the change during one timestep only.
1871 @lilypond[quote,fragment,verbatim]
1873 \once \override Stem.thickness = #4.0
1878 The @code{\override} must be done before the object is
1879 started. Therefore, when altering @emph{Spanner} objects such as slurs
1880 or beams, the @code{\override} command must be executed at the moment
1881 when the object is created. In this example,
1883 @lilypond[quote,fragment,verbatim]
1884 \override Slur.thickness = #3.0
1886 \override Beam.beam-thickness = #0.6
1891 the slur is fatter but the beam is not. This is because the command for
1892 @code{Beam} comes after the Beam is started, so it has no effect.
1894 Analogous to @code{\unset}, the @code{\revert} command for a context
1895 undoes an @code{\override} command; like with @code{\unset}, it only
1896 affects settings that were made in the same context. In other words, the
1897 @code{\revert} in the next example does not do anything.
1900 \override Voice.Stem.thickness = #4.0
1901 \revert Staff.Stem.thickness
1904 Some tweakable options are called @q{subproperties} and reside inside
1905 properties. To tweak those, use commands of the form
1907 @c leave this as a long long
1909 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
1916 \override Stem.details.beamed-lengths = #'(4 4 3)
1922 Internals Reference:
1923 @rinternals{Backend},
1924 @rinternals{All layout objects},
1925 @rinternals{OverrideProperty},
1926 @rinternals{RevertProperty},
1927 @rinternals{PropertySet}.
1930 The back-end is not very strict in type-checking object properties.
1931 Cyclic references in Scheme values for properties can cause hangs
1932 or crashes, or both.
1935 @node The set command
1936 @subsection The @code{@bs{}set} command
1940 @cindex changing properties
1942 Each context has a set of @emph{properties}, variables contained
1943 in that context. Context properties are changed with the @code{\set}
1944 command, which has the following syntax:
1947 \set @var{context}.@var{property} = #@var{value}
1950 @var{value} is a Scheme object, which is why it must be preceded by
1951 the @code{#}@tie{}character.
1953 Contexts properties are usually named in
1954 @code{studlyCaps}. They mostly control the translation from
1955 music to notation, e.g., @code{localAlterations} (for determining
1956 whether to print accidentals), or @code{measurePosition} (for
1957 determining when to print a bar line). Context properties can
1958 change value over time while interpreting a piece of music;
1959 @code{measurePosition} is an obvious example of
1960 this. Context properties are modified with @code{\set}.
1962 For example, multimeasure rests will be combined into a single bar
1963 if the context property @code{skipBars} is set to @code{#t}:
1965 @lilypond[quote,fragment,verbatim]
1967 \set Score.skipBars = ##t
1971 If the @var{context} argument is left out, then the property will be
1972 set in the current bottom context (typically @code{ChordNames},
1973 @code{Voice}, @code{TabVoice}, or @code{Lyrics}).
1975 @lilypond[quote,fragment,verbatim]
1976 \set Score.autoBeaming = ##f
1979 \set autoBeaming = ##t
1987 The change is applied @q{on-the-fly}, during the music, so that the
1988 setting only affects the second group of eighth notes.
1990 Note that the bottom-most context does not always contain the property
1991 that you wish to change -- for example, attempting to set the
1992 @code{skipBars} property of the default bottom context, in this case
1993 @code{Voice}, will have no effect, because skipBars is a property of
1994 the @code{Score} context.
1996 @lilypond[quote,fragment,verbatim]
2002 Contexts are hierarchical, so if an enclosing context was specified, for
2003 example @code{Staff}, then the change would also apply to all
2004 @code{Voice}s in the current staff.
2008 The @code{\unset} command:
2011 \unset @var{context}.@var{property}
2015 is used to remove the definition of @var{property} from
2016 @var{context}. This command removes
2017 the definition only if it is set in @var{context}.
2018 Properties that have been set in enclosing contexts will
2019 not be altered by an unset in an enclosed context:
2021 @lilypond[quote,fragment,verbatim]
2022 \set Score.autoBeaming = ##t
2026 \unset Score.autoBeaming
2034 Like @code{\set}, the @var{context} argument does not have to be
2035 specified for a bottom context, so the two statements
2038 \set Voice.autoBeaming = ##t
2039 \set autoBeaming = ##t
2043 are equivalent if the current bottom context is @code{Voice}.
2047 Preceding a @code{\set} or @code{\unset} command by @code{\once}
2048 makes the setting apply to only a single time-step:
2050 @lilypond[quote,fragment,verbatim]
2052 \once \set fontSize = #4.7
2057 A full description of all available context properties is in the
2058 internals reference, see
2060 @rinternals{Tunable context properties}.
2063 Translation @expansion{} Tunable context properties.
2067 Internals Reference:
2068 @rinternals{Tunable context properties}.
2071 @node The override command
2072 @subsection The @code{\override} command
2074 @cindex grob properties
2075 @cindex properties, grob
2078 There is a special type of context property: the grob
2079 description. Grob descriptions are named in @code{StudlyCaps}
2080 (starting with capital letters). They contain the
2081 @q{default settings} for a particular kind of grob as an
2082 association list. See @file{scm/define-grobs.scm}
2083 to see the settings for each grob description. Grob descriptions
2084 are modified with @code{\override}.
2086 The syntax for the @code{\override} command is
2089 \override [@var{context}.]@var{GrobName}.@var{property} = #@var{value}
2092 For example, we can increase the thickness of a note stem by
2093 overriding the @code{thickness} property of the @code{Stem}
2096 @lilypond[quote,fragment,verbatim]
2098 \override Voice.Stem.thickness = #3.0
2102 If no context is specified in an @code{\override}, the bottom
2105 @lilypond[quote,fragment,verbatim]
2106 \override Staff.Stem.thickness = #3.0
2110 \override Stem.thickness = #0.5
2119 Some tweakable options are called @q{subproperties} and reside inside
2120 properties. To tweak those, use commands in the form
2123 \override Stem.details.beamed-lengths = #'(4 4 3)
2126 or to modify the ends of spanners, use a form like these
2129 \override TextSpanner.bound-details.left.text = #"left text"
2130 \override TextSpanner.bound-details.right.text = #"right text"
2134 @cindex reverting overrides
2135 @cindex overrides, reverting
2137 The effects of @code{\override} can be undone by @code{\revert}.
2139 The syntax for the @code{\revert} command is
2142 \revert [@var{context}.]@var{GrobName}.@var{property}
2147 @lilypond[quote,verbatim]
2150 \override Voice.Stem.thickness = #3.0
2152 \revert Voice.Stem.thickness
2157 The effects of @code{\override} and @code{\revert} apply to all
2158 grobs in the affected context from the current time forward:
2160 @lilypond[quote,verbatim]
2164 \override Staff.Stem.thickness = #3.0
2169 \revert Staff.Stem.thickness
2176 @cindex overriding for only one moment
2178 @code{\once} can be used with @code{\override} or @code{\revert}
2179 to affect only the current time step:
2181 @lilypond[quote,verbatim]
2184 \override Stem.thickness = #3.0
2189 \once \override Stem.thickness = #3.0
2197 Commands which change output generally look like
2200 \override Voice.Stem.thickness = #3.0
2204 To construct this tweak we must determine these bits of information:
2207 @item the context: here @code{Voice}.
2208 @item the layout object: here @code{Stem}.
2209 @item the layout property: here @code{thickness}.
2210 @item a sensible value: here @code{3.0}.
2213 @cindex internal documentation
2214 @cindex finding graphical objects
2215 @cindex graphical object descriptions
2218 @cindex internal documentation
2220 For many properties, regardless of the data type of the property, setting the
2221 property to false (@code{#f}) will result in turning it off, causing
2222 LilyPond to ignore that property entirely. This is particularly useful for
2223 turning off grob properties which may otherwise be causing problems.
2225 We demonstrate how to glean this information from the notation manual
2226 and the program reference.
2230 Internals Reference:
2231 @rinternals{Backend}
2234 @node The tweak command
2235 @subsection The @code{\tweak} command
2240 Changing grob properties
2241 with @code{\override} causes the changes to apply to all of the
2242 given grobs in the context at the moment the change applies.
2243 Sometimes, however, it is desirable to have changes apply to just
2244 one grob, rather than to all grobs in the affected context. This is
2245 accomplished with the @code{\tweak} command, which has the following
2249 \tweak [@var{layout-object}.]@var{grob-property} @var{value}
2252 Specifying @var{layout-object} is optional.
2253 The @code{\tweak} command applies to the music object that immediately
2254 follows @var{value} in the music stream.
2257 In some cases, it is possible to take a short-cut for tuning
2258 graphical objects. For objects that are created directly from
2259 an item in the input file, you can use the @code{\tweak} command.
2262 @lilypond[verbatim,quote]
2268 \tweak duration-log #1
2278 The main use of the @code{\tweak} command is to modify just
2279 one of a number of notation elements which start at the same musical
2280 moment, like the notes of a chord, or tuplet brackets which start
2283 The @code{\tweak} command sets a property in the following object
2284 directly, without requiring the grob name or context to be
2285 specified. For this to work, it is necessary for the @code{\tweak}
2286 command to remain immediately adjacent to the object to which it is
2287 to apply after the input file has been converted to a music stream.
2288 This is often not the case, as many additional elements are inserted
2289 into the music stream implicitly. For example, when a note which is
2290 not part of a chord is processed, LilyPond implicitly inserts a
2291 @code{ChordEvent} event before the note, so separating the tweak
2292 from the note. However, if chord symbols are placed round the
2293 tweak and the note, the @code{\tweak} command comes after the
2294 @code{ChordEvent} in the music stream, so remaining adjacent to the
2295 note, and able to modify it.
2299 @lilypond[verbatim,fragment,quote]
2300 <\tweak color #red c''>4
2306 @lilypond[verbatim,fragment,quote]
2307 \tweak color #red c''4
2312 For an introduction to the syntax and uses of the tweak command
2313 see @rlearning{Tweaking methods}.
2315 When several similar items are placed at the same musical moment,
2316 the @code{\override} command cannot be used to modify just one of
2317 them -- this is where the @code{\tweak} command must be used.
2318 Items which may appear more than once at the same musical moment
2319 include the following:
2321 @c TODO expand to include any further uses of \tweak
2323 @item note heads of notes inside a chord
2324 @item articulation signs on a single note
2325 @item ties between notes in a chord
2326 @item tuplet brackets starting at the same time
2329 @c TODO add examples of these
2331 @cindex chord, modifying one note in
2333 In this example, the color of one note head and the type of another
2334 note head are modified within a single chord:
2336 @lilypond[verbatim,fragment,quote]
2341 \tweak duration-log #1
2346 @code{\tweak} can be used to modify slurs:
2348 @lilypond[verbatim,quote]
2349 \relative { c'-\tweak thickness #5 ( d e f) }
2353 For the @code{\tweak} command to work, it must
2354 remain immediately adjacent to the object to which it is
2355 to apply after the input file has been converted to a music stream.
2356 Tweaking a whole chord does not do anything since its music event
2357 only acts as a container, and all layout objects are created from events
2358 inside of the @code{EventChord}:
2360 @lilypond[verbatim,fragment,quote]
2361 \tweak color #red c''4
2362 \tweak color #red <c'' e''>4
2363 <\tweak color #red c'' e''>4
2366 The simple @code{\tweak} command cannot be used to modify any object
2367 that is not directly created from the input. In particular
2368 it will not affect stems, automatic
2369 beams or accidentals, since these are generated later by
2370 @code{NoteHead} layout objects rather than by music elements in the
2373 Such indirectly created layout objects can be tweaked using the form
2374 of the @code{\tweak} command in which the grob name is specified
2377 @lilypond[fragment,verbatim,quote]
2378 \tweak Stem.color #red
2379 \tweak Beam.color #green c''8 e''
2380 <c'' e'' \tweak Accidental.font-size #-3 ges''>4
2383 @code{\tweak} cannot be used to modify clefs or time
2384 signatures, since these become separated from any preceding
2385 @code{\tweak} command in the input stream by the automatic
2386 insertion of extra elements required to specify the context.
2388 Several @code{\tweak} commands may be placed before a
2389 notational element -- all affect it:
2391 @lilypond[verbatim,fragment,quote]
2393 -\tweak style #'dashed-line
2394 -\tweak dash-fraction #0.2
2395 -\tweak thickness #3
2401 The music stream which is generated from a section of an input file,
2402 including any automatically inserted elements, may be examined,
2403 see @rextend{Displaying music expressions}. This may be helpful in
2404 determining what may be modified by a @code{\tweak} command, or
2405 in determining how to adjust the input to make a @code{\tweak}
2410 @rlearning{Tweaking methods}.
2413 @rextend{Displaying music expressions}.
2417 @cindex tweaking control points
2418 @cindex control points, tweaking
2420 The @code{\tweak} command cannot be used to modify the control
2421 points of just one of several ties in a chord, other than the first
2422 one encountered in the input file.
2424 @node set versus override
2425 @subsection @code{\set} vs. @code{\override}
2427 @c TODO Should't a bunch of that be explained earlier?
2432 The @code{\set} and @code{\override} commands manipulate properties
2433 associated with contexts. In both cases, the properties follow a
2434 @emph{hierarchy of contexts}; properties that are not set themselves in
2435 a context will still show the values of their respective parent's
2438 The lifetime and value of a context property is dynamic and only
2439 available when music is being interpreted (i.e., @q{iterated}). At the
2440 time of the context's creation, properties are initialized from its
2441 corresponding definitions (along with any other modifications) of that
2442 context. Any subsequent changes are achieved with any
2443 @q{property-setting} commands that are within the music itself.
2445 Graphical Object (or @qq{grob}) definitions are a @emph{special}
2446 category of context properties as their structure and use is different
2447 from that of normal context properties. Unlike normal context
2448 properties, grob definitions are subdivided into @emph{grob properties}.
2450 Also, in contrast to normal context properties, grob definitions have
2451 their own internal @q{bookkeeping} used to keep track of their own
2452 individual grob properties and any sub-properties. This means that it
2453 is possible to define those parts within different contexts and yet
2454 still have the overall grob definition at the time of grob creation from
2455 all the pieces provided amongst the current context and its parent(s).
2457 A grob is usually created by an engraver at the time of interpreting a
2458 music expression and receives its initial properties from the current
2459 grob definition of the engraver's context. The engraver (or other
2460 @q{backend} parts of LilyPond) can then change (or add to) the grob's
2461 initial properties. However, this does not affect the context's own
2464 What LilyPond calls @emph{grob properties} in the context of
2465 @q{user-level} tweaks are really the properties of a @emph{context's}
2466 own grob definition.
2468 Grob definitions are accessed with a different set of commands and are
2469 manipulated using @code{\override} and @code{\revert} and have a name
2470 starting with a capital letter (e.g., @samp{NoteHead}); whereas normal
2471 context properties are manipulated using @code{\set} and @code{\unset}
2472 and are named starting with a lowercase letter.
2474 @cindex tweak, relation to @code{\override}
2476 @funindex \overrideProperty
2478 The commands @code{\tweak} and @code{\overrideProperty} change grob
2479 properties by bypassing all context properties completely and, instead,
2480 catch grobs as they are being created, setting properties on them for
2481 a music event (@code{\tweak}) or, in the case of
2482 @code{\overrideProperty} for a specific override.
2485 @node Modifying alists
2486 @subsection Modifying alists
2488 Some user-configurable properties are internally represented as
2489 @emph{alists} (association lists), which store pairs of
2490 @emph{keys} and @emph{values}. The structure of an alist is:
2493 '((@var{key1} . @var{value1})
2494 (@var{key2} . @var{value2})
2495 (@var{key3} . @var{value3})
2499 If an alist is a grob property or @code{\paper} variable, its keys
2500 can be modified individually without affecting other keys.
2502 For example, to reduce the space between adjacent staves in a
2503 staff-group, use the @code{staff-staff-spacing} property of the
2504 @code{StaffGrouper} grob. The property is an alist with four
2505 keys: @code{basic-distance}, @code{minimum-distance},
2506 @code{padding}, and @code{stretchability}. The standard settings
2507 for this property are listed in the @qq{Backend} section of the
2508 Internals Reference (see @rinternals{StaffGrouper}):
2511 '((basic-distance . 9)
2512 (minimum-distance . 7)
2514 (stretchability . 5))
2517 One way to bring the staves closer together is by reducing the
2518 value of the @code{basic-distance} key (@code{9}) to match the
2519 value of @code{minimum-distance} (@code{7}). To modify a single
2520 key individually, use a @emph{nested declaration}:
2522 @lilypond[quote,verbatim]
2523 % default space between staves
2525 \new Staff { \clef treble c''1 }
2526 \new Staff { \clef bass c1 }
2529 % reduced space between staves
2530 \new PianoStaff \with {
2531 % this is the nested declaration
2532 \override StaffGrouper.staff-staff-spacing.basic-distance = #7
2534 \new Staff { \clef treble c''1 }
2535 \new Staff { \clef bass c1 }
2539 Using a nested declaration will update the specified key (such as
2540 @code{basic-distance} in the above example) without altering any
2541 other keys already set for the same property.
2543 Now suppose we want the staves to be as close as possible without
2544 overlapping. The simplest way to do this is to set all four alist
2545 keys to zero. However, it is not necessary to enter four nested
2546 declarations, one for each key. Instead, the property can be
2547 completely re-defined with one declaration, as an alist:
2549 @lilypond[quote,verbatim]
2550 \new PianoStaff \with {
2551 \override StaffGrouper.staff-staff-spacing =
2552 #'((basic-distance . 0)
2553 (minimum-distance . 0)
2555 (stretchability . 0))
2557 \new Staff { \clef treble c''1 }
2558 \new Staff { \clef bass c1 }
2562 Note that any keys not explicitly listed in the alist definition
2563 will be reset to their @emph{default-when-unset} values. In the
2564 case of @code{staff-staff-spacing}, any unset key-values would be
2565 reset to zero (except @code{stretchability}, which takes the value
2566 of @code{basic-distance} when unset). Thus the following two
2567 declarations are equivalent:
2570 \override StaffGrouper.staff-staff-spacing =
2571 #'((basic-distance . 7))
2573 \override StaffGrouper.staff-staff-spacing =
2574 #'((basic-distance . 7)
2575 (minimum-distance . 0)
2577 (stretchability . 7))
2580 One (possibly unintended) consequence of this is the removal of
2581 any standard settings that are set in an initialization file and
2582 loaded each time an input file is compiled. In the above example,
2583 the standard settings for @code{padding} and
2584 @code{minimum-distance} (defined in @file{scm/define-grobs.scm})
2585 are reset to their default-when-unset values (zero for both keys).
2586 Defining a property or variable as an alist (of any size) will
2587 always reset all unset key-values to their default-when-unset
2588 values. Unless this is the intended result, it is safer to update
2589 key-values individually with a nested declaration.
2591 @warning{Nested declarations will not work for context property
2592 alists (such as @code{beamExceptions}, @code{keyAlterations},
2593 @code{timeSignatureSettings}, etc.). These properties can only be
2594 modified by completely re-defining them as alists.}
2597 @node Useful concepts and properties
2598 @section Useful concepts and properties
2603 * Direction and placement::
2604 * Distances and measurements::
2606 * Staff symbol properties::
2608 * Visibility of objects::
2610 * Rotating objects::
2614 @subsection Input modes
2616 The way in which the notation contained within an input file is
2617 interpreted is determined by the current input mode.
2619 @subsubsubheading Chord mode
2621 This is activated with the @code{\chordmode} command, and causes
2622 input to be interpreted with the syntax of chord notation, see
2623 @ref{Chord notation}. Chords are rendered as notes on a staff.
2625 Chord mode is also activated with the @code{\chords} command.
2626 This also creates a new @code{ChordNames} context and
2627 causes the following input to be interpreted with the syntax of
2628 chord notation and rendered as chord names in the @code{ChordNames}
2629 context, see @ref{Printing chord names}.
2631 @subsubsubheading Drum mode
2633 This is activated with the @code{\drummode} command, and causes
2634 input to be interpreted with the syntax of drum notation, see
2635 @ref{Basic percussion notation}.
2637 Drum mode is also activated with the @code{\drums} command.
2638 This also creates a new @code{DrumStaff} context and causes the
2639 following input to be interpreted with the syntax of drum notation
2640 and rendered as drum symbols on a drum staff, see
2641 @ref{Basic percussion notation}.
2643 @subsubsubheading Figure mode
2645 This is activated with the @code{\figuremode} command, and causes
2646 input to be interpreted with the syntax of figured bass, see
2647 @ref{Entering figured bass}.
2649 Figure mode is also activated with the @code{\figures} command.
2650 This also creates a new @code{FiguredBass} context and causes the
2651 following input to be interpreted with the figured bass syntax
2652 and rendered as figured bass symbols in the @code{FiguredBass}
2653 context, see @ref{Introduction to figured bass}.
2655 @subsubsubheading Fret and tab modes
2657 There are no special input modes for entering fret and tab symbols.
2659 To create tab diagrams, enter notes or chords in note mode and
2660 render them in a @code{TabStaff} context, see
2661 @ref{Default tablatures}.
2663 To create fret diagrams above a staff, you have two choices.
2664 You can either use the @code{FretBoards} context (see
2665 @ref{Automatic fret diagrams}) or you can enter them as a markup
2666 above the notes using the @code{\fret-diagram} command (see
2667 @ref{Fret diagram markups}).
2669 @subsubsubheading Lyrics mode
2671 This is activated with the @code{\lyricmode} command, and causes
2672 input to be interpreted as lyric syllables with optional durations
2673 and associated lyric modifiers, see @ref{Vocal music}.
2675 Lyric mode is also activated with the @code{\addlyrics} command.
2676 This also creates a new @code{Lyrics} context and an implicit
2677 @code{\lyricsto} command which associates the following lyrics
2678 with the preceding music.
2680 @subsubsubheading Markup mode
2682 This is activated with the @code{\markup} command, and causes
2683 input to be interpreted with the syntax of markup, see
2684 @ref{Text markup commands}.
2686 @subsubsubheading Note mode
2688 This is the default mode or it may be activated with the
2689 @code{\notemode} command. Input is interpreted as pitches,
2690 durations, markup, etc and typeset as musical notation on a staff.
2692 It is not normally necessary to specify note mode explicitly, but
2693 it may be useful to do so in certain situations, for example if you
2694 are in lyric mode, chord mode or any other mode and want to insert
2695 something that only can be done with note mode syntax.
2698 @node Direction and placement
2699 @subsection Direction and placement
2701 In typesetting music the direction and placement of many items is
2702 a matter of choice. For example, the stems of notes can
2703 be directed up or down; lyrics, dynamics, and other expressive
2704 marks may be placed above or below the staff; text may be aligned
2705 left, right or center; etc. Most of these choices may be left to
2706 be determined automatically by LilyPond, but in some cases it may
2707 be desirable to force a particular direction or placement.
2710 * Articulation direction indicators::
2711 * The direction property::
2715 @node Articulation direction indicators
2716 @unnumberedsubsubsec Articulation direction indicators
2718 By default some directions are always up or always down (e.g.,
2719 dynamics or fermata), while other things can alternate between
2720 up or down based on the stem direction (like slurs or accents).
2722 @c TODO Add table showing these
2724 The default action may be overridden by prefixing the articulation
2725 by a @emph{direction indicator}. Three direction indicators are
2726 available: @code{^} (meaning @qq{up}), @code{_} (meaning @qq{down})
2727 and @code{-} (meaning @qq{use default direction}). The direction
2728 indicator can usually be omitted, in which case @code{-} is assumed,
2729 but a direction indicator is @strong{always} required before
2732 @item @code{\tweak} commands
2733 @item @code{\markup} commands
2734 @item @code{\tag} commands
2735 @item string markups, e.g., -"string"
2736 @item fingering instructions, e.g., @w{@code{-1}}
2737 @item articulation shortcuts, e.g., @w{@code{-.}}, @w{@code{->}}, @w{@code{--}}
2740 Direction indicators affect only the next note:
2742 @lilypond[verbatim,quote]
2752 @node The direction property
2753 @unnumberedsubsubsec The direction property
2755 The position or direction of many layout objects is controlled by the
2756 @code{direction} property.
2758 The value of the @code{direction} property may be set to @code{1},
2759 meaning @qq{up} or @qq{above}, or to @w{@code{-1}}, meaning @qq{down} or
2760 @qq{below}. The symbols @code{UP} and @code{DOWN} may be used instead
2761 of @code{1} and @w{@code{-1}} respectively. The default direction may
2762 be specified by setting @code{direction} to @code{0} or @code{CENTER}.
2763 Alternatively, in many cases predefined commands exist to specify the
2764 direction. These are of the form
2767 \xxxUp, \xxxDown or \xxxNeutral
2771 where @code{\xxxNeutral} means @qq{use the default} direction.
2772 See @rlearning{Within-staff objects}.
2774 In a few cases, arpeggio for example, the value of the @code{direction}
2775 property can specify whether the object is to be placed to the right or
2776 left of the parent. In this case @w{@code{-1}} or @code{LEFT} means
2777 @qq{to the left} and @code{1} or @code{RIGHT} means @qq{to the right}.
2778 @code{0} or @code{CENTER} means @qq{use the default} direction.
2781 These all have side-axis set to #X
2782 AmbitusAccidental - direction has no effect
2784 StanzaNumber - not tried
2785 TrillPitchAccidental - not tried
2786 TrillPitchGroup - not tried
2789 These indications affect all notes until they are canceled.
2791 @lilypond[verbatim,quote]
2802 In polyphonic music, it is generally better to specify an explicit
2803 @code{voice} than change an object's direction. For more information,
2804 see @ref{Multiple voices}.
2808 @rlearning{Within-staff objects}.
2811 @ref{Multiple voices}.
2814 @node Distances and measurements
2815 @subsection Distances and measurements
2817 @cindex distances, absolute
2818 @cindex distances, scaled
2825 Distances in LilyPond are of two types: absolute and scaled.
2827 Absolute distances are used for specifying margins, indents, and
2828 other page layout details, and are by default specified in
2829 millimeters. Distances may be specified in other units by
2830 following the quantity by @code{\mm}, @code{\cm},
2831 @code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27 of
2832 an inch). Page layout distances can also be specified in scalable
2833 units (see the following paragraph) by appending
2834 @code{\staff-space} to the quantity. Page layout is described in
2835 detail in @ref{Page layout}.
2837 Scaled distances are always specified in units of the staff-space
2838 or, rarely, the half staff-space. The staff-space is the distance
2839 between two adjacent staff lines. The default value can be changed
2840 globally by setting the global staff size, or it can be overridden
2841 locally by changing the @code{staff-space} property of
2842 @code{StaffSymbol}. Scaled distances automatically scale with any
2843 change to the either the global staff size or the
2844 @code{staff-space} property of @code{StaffSymbol}, but fonts scale
2845 automatically only with changes to the global staff size.
2846 The global staff size thus enables the overall size of a rendered
2847 score to be easily varied. For the methods of setting the global
2848 staff size see @ref{Setting the staff size}.
2852 If just a section of a score needs to be rendered to a different
2853 scale, for example an ossia section or a footnote, the global staff
2854 size cannot simply be changed as this would affect the entire score.
2855 In such cases the change in size is made by overriding both the
2856 @code{staff-space} property of @code{StaffSymbol} and the size of
2857 the fonts. A Scheme function, @code{magstep}, is available to
2858 convert from a font size change to the equivalent change in
2859 @code{staff-space}. For an explanation and an example of its use,
2860 see @rlearning{Length and thickness of objects}.
2864 @rlearning{Length and thickness of objects}.
2868 @ref{Setting the staff size}.
2872 @subsection Dimensions
2875 @cindex bounding box
2877 The dimensions of a graphical object specify the positions of the left
2878 and right edges and the bottom and top edges of the objects' bounding
2879 box as distances from the objects' reference point in units of
2880 staff-spaces. These positions are usually coded as two Scheme pairs.
2881 For example, the text markup command @code{\with-dimensions} takes
2882 three arguments, the first two of which are a Scheme pair giving the
2883 left and right edge positions and a Scheme pair giving the bottom and
2887 \with-dimensions #'(-5 . 10) #'(-3 . 15) @var{arg}
2890 This specifies a bounding box for @var{arg} with its left edge at -5,
2891 its right edge at 10, its bottom edge at -3 and its top edge at 15,
2892 all measured from the objects' reference point in units of
2897 @ref{Distances and measurements}.
2900 @node Staff symbol properties
2901 @subsection Staff symbol properties
2903 @cindex adjusting staff symbol
2904 @cindex drawing staff symbol
2905 @cindex staff symbol, setting of
2907 @c TODO Extend or remove this section. See also NR 1.6.2 Staff symbol
2908 @c Need to think of uses for these properties. Eg 'line-positions
2909 @c is used in a snippet to thicken centre line.
2910 @c If retained, add @ref to here in 1.6.2 -td
2912 The vertical position of staff lines and the number of staff lines
2913 can be defined at the same time. As the following example shows,
2914 note positions are not influenced by the staff line positions.
2916 @warning{The @code{'line-positions} property overrides the
2917 @code{'line-count} property. The number of staff lines is
2918 implicitly defined by the number of elements in the list of values
2919 for @code{'line-positions}.}
2921 @lilypond[verbatim,quote]
2923 \override StaffSymbol.line-positions = #'(7 3 0 -4 -6 -7)
2925 \relative { a4 e' f b | d1 }
2928 The width of a staff can be modified. The units are staff
2929 spaces. The spacing of objects inside the staff is not affected by
2932 @lilypond[verbatim,quote]
2934 \override StaffSymbol.width = #23
2936 \relative { a4 e' f b | d1 }
2941 @subsection Spanners
2943 Many objects of musical notation extend over several notes or even
2944 several bars. Examples are slurs, beams, tuplet brackets, volta
2945 repeat brackets, crescendi, trills, and glissandi. Such objects
2946 are collectively called @qq{spanners}, and have special properties to control
2947 their appearance and behaviour. Some of these properties are common
2948 to all spanners; others are restricted to a sub-set of the spanners.
2950 All spanners support the @code{spanner-interface}. A few, essentially
2951 those that draw a straight line between the two objects, support in
2952 addition the @code{line-spanner-interface}.
2955 * Using the spanner-interface::
2956 * Using the line-spanner-interface::
2959 @node Using the spanner-interface
2960 @unnumberedsubsubsec Using the @code{spanner-interface}
2962 This interface provides two properties that apply to several spanners.
2964 @subsubsubheading The @code{minimum-length} property
2966 The minimum length of the spanner is specified by the
2967 @code{minimum-length} property. Increasing this usually has the
2968 necessary effect of increasing the spacing of the notes between the
2969 two end points. However, this override has no effect on
2970 many spanners, as their length is determined by other considerations.
2971 A few examples where it is effective are shown below.
2981 Works as long as callback is made:
2985 Works not at all for:
2994 @lilypond[verbatim,quote,fragment]
2997 % increase the length of the tie
2998 -\tweak minimum-length #5
3002 @lilypond[verbatim,quote]
3003 \relative \compressMMRests {
3006 % increase the length of the rest bar
3007 \once \override MultiMeasureRest.minimum-length = #20
3013 @lilypond[verbatim,quote]
3016 % increase the length of the hairpin
3017 \override Hairpin.minimum-length = #20
3022 This override can also be used to increase the length of slurs and
3025 @lilypond[verbatim,quote]
3029 -\tweak minimum-length #5
3034 -\tweak minimum-length #5
3039 For some layout objects, the @code{minimum-length} property becomes
3040 effective only if the @code{set-spacing-rods} procedure is called
3041 explicitly. To do this, the @code{springs-and-rods} property should
3042 be set to @code{ly:spanner::set-spacing-rods}. For example,
3043 the minimum length of a glissando has no effect unless the
3044 @code{springs-and-rods} property is set:
3046 @lilypond[verbatim,fragment,quote]
3050 % not effective alone
3051 \once \override Glissando.minimum-length = #20
3054 % effective only when both overrides are present
3055 \once \override Glissando.minimum-length = #20
3056 \once \override Glissando.springs-and-rods = #ly:spanner::set-spacing-rods
3060 The same is true of the @code{Beam} object:
3062 @lilypond[verbatim,fragment,quote]
3063 % not effective alone
3064 \once \override Beam.minimum-length = #20
3067 % effective only when both overrides are present
3068 \once \override Beam.minimum-length = #20
3069 \once \override Beam.springs-and-rods = #ly:spanner::set-spacing-rods
3073 @subsubsubheading The @code{to-barline} property
3075 The second useful property of the @code{spanner-interface} is
3076 @code{to-barline}. By default this is true, causing hairpins and
3077 other spanners which are terminated on the first note of a measure to
3078 end instead on the immediately preceding bar line. If set to false,
3079 the spanner will extend beyond the bar line and end on the note
3082 @lilypond[verbatim,quote]
3084 a' \< a a a a \! a a a \break
3085 \override Hairpin.to-barline = ##f
3086 a \< a a a a \! a a a
3090 This property is not effective for all spanners. For example,
3091 setting it to @code{#t} has no effect on slurs or phrasing slurs
3092 or on other spanners for which terminating on the bar line would
3095 @node Using the line-spanner-interface
3096 @unnumberedsubsubsec Using the @code{line-spanner-interface}
3098 Objects which support the @code{line-spanner-interface} include
3101 @item @code{DynamicTextSpanner}
3102 @item @code{Glissando}
3103 @item @code{TextSpanner}
3104 @item @code{TrillSpanner}
3105 @item @code{VoiceFollower}
3108 The routine responsible for drawing the stencils for these spanners is
3109 @code{ly:line-spanner::print}. This routine determines the
3110 exact location of the two end points and draws a line
3111 between them, in the style requested. The locations of the two
3112 end points of the spanner are computed on-the-fly, but it is
3113 possible to override their Y-coordinates. The
3114 properties which need to be specified are nested
3115 two levels down within the property hierarchy, but the syntax of
3116 the @code{\override} command is quite simple:
3118 @lilypond[quote,fragment,verbatim]
3120 \once \override Glissando.bound-details.left.Y = #3
3121 \once \override Glissando.bound-details.right.Y = #-2
3125 The units for the @code{Y} property are @code{staff-space}s,
3126 with the center line of the staff being the zero point.
3127 For the glissando, this is the value for @code{Y} at the
3128 X-coordinate corresponding to the center point of each note head,
3129 if the line is imagined to be extended to there.
3131 If @code{Y} is not set, the value is computed from the vertical
3132 position of the corresponding attachment point of the spanner.
3134 In case of a line break, the values for the end points are
3135 specified by the @code{left-broken} and @code{right-broken}
3136 sub-lists of @code{bound-details}. For example:
3138 @lilypond[ragged-right,fragment,verbatim,quote]
3139 \override Glissando.breakable = ##t
3140 \override Glissando.bound-details.right-broken.Y = #-3
3141 c''1 \glissando \break
3146 A number of further properties of the @code{left} and
3147 @code{right} sub-lists of the @code{bound-details} property
3148 may be modified in the same way as @code{Y}:
3152 This sets the Y-coordinate of the end point, in @code{staff-space}s
3153 offset from the staff center line. By default, it is the center of
3154 the bound object, so a glissando points to the vertical center of
3157 For horizontal spanners, such as text spanners and trill spanners,
3158 it is hardcoded to 0.
3161 This determines where the line starts and ends in the X-direction,
3162 relative to the bound object. So, a value of @w{@code{-1}} (or
3163 @code{LEFT}) makes the line start/end at the left side of the note
3164 head it is attached to.
3167 This is the absolute X-coordinate of the end point. It is usually
3168 computed on the fly, and overriding it has little useful effect.
3171 Line spanners may have symbols at the beginning or end, which is
3172 contained in this sub-property. This is for internal use; it is
3173 recommended that @code{text} be used instead.
3176 This is a markup that is evaluated to yield the stencil. It is used
3177 to put @i{cresc.}, @i{tr} and other text on horizontal spanners.
3179 @lilypond[quote,ragged-right,fragment,verbatim]
3180 \override TextSpanner.bound-details.left.text
3181 = \markup { \small \bold Slower }
3182 \relative { c''2\startTextSpan b c a\stopTextSpan }
3185 @item stencil-align-dir-y
3186 @item stencil-offset
3187 Without setting one of these, the stencil is simply put at the
3188 end-point, centered on the line, as defined by the @code{X} and
3189 @code{Y} sub-properties. Setting either @code{stencil-align-dir-y}
3190 or @code{stencil-offset} will move the symbol at the edge vertically
3191 relative to the end point of the line:
3193 @lilypond[quote,fragment,verbatim]
3194 \override TextSpanner.bound-details.left.stencil-align-dir-y = #-2
3195 \override TextSpanner.bound-details.right.stencil-align-dir-y = #UP
3197 \override TextSpanner.bound-details.left.text = #"ggg"
3198 \override TextSpanner.bound-details.right.text = #"hhh"
3200 \relative { c'4^\startTextSpan c c c \stopTextSpan }
3203 Note that negative values move the text @emph{up}, contrary to the
3204 effect that might be expected, as a value of @w{@code{-1}} or
3205 @code{DOWN} means align the @emph{bottom} edge of the text with
3206 the spanner line. A value of @code{1} or @code{UP} aligns
3207 the top edge of the text with the spanner line.
3210 Setting this sub-property to @code{#t} produces an arrowhead at the
3211 end-points of the line.
3214 This sub-property controls the space between the specified
3215 end point of the line and the actual end. Without padding, a
3216 glissando would start and end in the center of each note head.
3220 The music function @code{\endSpanners} terminates the spanner
3221 which starts on the immediately following note prematurely. It
3222 is terminated after exactly one note, or at the following bar line
3223 if @code{to-barline} is true and a bar line occurs before the next
3226 @lilypond[verbatim,quote,ragged-right]
3229 c2 \startTextSpan c2 c2
3235 When using @code{\endSpanners} it is not necessary to close
3236 \startTextSpan with \stopTextSpan, nor is it necessary to close
3237 hairpins with @code{\!}.
3240 Internals Reference:
3241 @rinternals{TextSpanner},
3242 @rinternals{Glissando},
3243 @rinternals{VoiceFollower},
3244 @rinternals{TrillSpanner},
3245 @rinternals{line-spanner-interface}.
3248 @node Visibility of objects
3249 @subsection Visibility of objects
3251 @cindex objects, visibility of
3252 @cindex grobs, visibility of
3253 @cindex visibility of objects
3255 There are four main ways in which the visibility of layout objects
3256 can be controlled: their stencil can be removed, they can be made
3257 transparent, they can be colored white, or their
3258 @code{break-visibility} property can be overridden. The first
3259 three apply to all layout objects; the last to just a few -- the
3260 @emph{breakable} objects. The Learning Manual introduces these
3261 four techniques, see @rlearning{Visibility and color of objects}.
3263 There are also a few other techniques which are specific to
3264 certain layout objects. These are covered under Special
3268 * Removing the stencil::
3269 * Making objects transparent::
3270 * Painting objects white::
3271 * Using break-visibility::
3272 * Special considerations::
3276 @node Removing the stencil
3277 @unnumberedsubsubsec Removing the stencil
3279 @cindex stencil, removing
3282 Every layout object has a stencil property. By default this is set
3283 to the specific function which draws that object. If this property
3284 is overridden to @code{#f} no function will be called and the object
3285 will not be drawn. The default action can be recovered with
3288 @lilypond[quote,fragment,verbatim]
3290 \override Score.BarLine.stencil = ##f
3292 \revert Score.BarLine.stencil
3296 This rather common operation has a shortcut @code{\omit}:
3298 @lilypond[quote,fragment,verbatim]
3302 \undo \omit Score.BarLine
3306 @node Making objects transparent
3307 @unnumberedsubsubsec Making objects transparent
3309 @cindex transparent, making objects
3312 Every layout object has a transparent property which by default is
3313 set to @code{#f}. If set to @code{#t} the object still occupies
3314 space but is made invisible.
3316 @lilypond[quote,fragment,verbatim]
3318 \once \override NoteHead.transparent = ##t
3322 This rather common operation has a shortcut @code{\hide}:
3324 @lilypond[quote,fragment,verbatim]
3326 \once \hide NoteHead
3330 @node Painting objects white
3331 @unnumberedsubsubsec Painting objects white
3333 @cindex objects, coloring
3334 @cindex coloring objects
3336 @cindex printing order
3337 @cindex overwriting objects
3338 @cindex objects, overwriting
3339 @cindex grobs, overwriting
3341 Every layout object has a color property which by default is set
3342 to @code{black}. If this is overridden to @code{white} the object
3343 will be indistinguishable from the white background. However,
3344 if the object crosses other objects the color of the crossing
3345 points will be determined by the order in which they are drawn,
3346 and this may leave a ghostly image of the white object, as shown
3349 @lilypond[quote,fragment,verbatim]
3350 \override Staff.Clef.color = #white
3354 This may be avoided by changing the order of printing the objects.
3355 All layout objects have a @code{layer} property which should be set
3356 to an integer. Objects with the lowest value of @code{layer} are
3357 drawn first, then objects with progressively higher values are drawn,
3358 so objects with higher values overwrite objects with lower values.
3359 By default most objects are assigned a @code{layer} value of
3360 @code{1}, although a few objects, including @code{StaffSymbol} and
3361 @code{BarLine}, are assigned a value of @code{0}. The order of
3362 printing objects with the same value of @code{layer} is indeterminate.
3364 In the example above the white clef, with a default @code{layer}
3365 value of @code{1}, is drawn after the staff lines (default
3366 @code{layer} value @code{0}), so overwriting them. To change this,
3367 the @code{Clef} object must be given in a lower value of
3368 @code{layer}, say @w{@code{-1}}, so that it is drawn earlier:
3370 @lilypond[quote,fragment,verbatim]
3371 \override Staff.Clef.color = #white
3372 \override Staff.Clef.layer = #-1
3376 @node Using break-visibility
3377 @unnumberedsubsubsec Using break-visibility
3379 @c TODO Add making other objects breakable
3381 @cindex break-visibility
3383 Most layout objects are printed only once, but some like
3384 bar lines, clefs, time signatures and key signatures, may need
3385 to be printed twice when a line break occurs -- once at the end
3386 of the line and again at the start of the next line. Such
3387 objects are called @emph{breakable}, and have a property, the
3388 @code{break-visibility} property to control their visibility
3389 at the three positions in which they may appear -- at the
3390 start of a line, within a line if they are changed, and at the
3391 end of a line if a change takes place there.
3393 For example, the time signature
3394 by default will be printed at the start of the first line, but
3395 nowhere else unless it changes, when it will be printed at the
3396 point at which the change occurs. If this change occurs at the
3397 end of a line the new time signature will be printed at the start
3398 of the next line and a cautionary time signature will be printed
3399 at the end of the previous line as well.
3401 This behaviour is controlled by the @code{break-visibility}
3402 property, which is explained in
3403 @c Leave this ref on a newline - formats incorrectly otherwise -td
3404 @rlearning{Visibility and color of objects}. This property takes
3405 a vector of three booleans which, in order, determine whether the
3406 object is printed at the end of, within the body of, or at the
3407 beginning of a line. Or to be more precise, before a line break,
3408 where there is no line break, or after a line break.
3410 Alternatively, these eight combinations may be specified
3411 by pre-defined functions, defined in @file{scm/output-lib.scm},
3412 where the last three columns indicate whether the layout objects
3413 will be visible in the positions shown at the head of the columns:
3415 @multitable {@code{begin-of-line-invisible}} {@code{#(#t #t #t)}} {Before} {At no} {After}
3416 @headitem Function @tab Vector @tab Before @tab At no @tab After
3417 @headitem form @tab form @tab break @tab break @tab break
3419 @item @code{all-visible} @tab @code{#(#t #t #t)} @tab yes @tab yes @tab yes
3420 @item @code{begin-of-line-visible} @tab @code{#(#f #f #t)} @tab no @tab no @tab yes
3421 @item @code{center-visible} @tab @code{#(#f #t #f)} @tab no @tab yes @tab no
3422 @item @code{end-of-line-visible} @tab @code{#(#t #f #f)} @tab yes @tab no @tab no
3423 @item @code{begin-of-line-invisible} @tab @code{#(#t #t #f)} @tab yes @tab yes @tab no
3424 @item @code{center-invisible} @tab @code{#(#t #f #t)} @tab yes @tab no @tab yes
3425 @item @code{end-of-line-invisible} @tab @code{#(#f #t #t)} @tab no @tab yes @tab yes
3426 @item @code{all-invisible} @tab @code{#(#f #f #f)} @tab no @tab no @tab no
3429 The default settings of @code{break-visibility} depend on the
3430 layout object. The following table shows all the layout objects
3431 of interest which are affected by @code{break-visibility} and the
3432 default setting of this property:
3434 @multitable @columnfractions .3 .3 .4
3436 @headitem Layout object @tab Usual context @tab Default setting
3438 @c omit Ambitus as it appears not to be affected by break-visibility -td
3439 @c @item @code{Ambitus} @tab as specified @tab @code{begin-of-line-visible}
3440 @item @code{BarLine} @tab @code{Score} @tab calculated
3441 @item @code{BarNumber} @tab @code{Score} @tab @code{begin-of-line-visible}
3442 @c omit the following item until it can be explained -td
3443 @c @item @code{BreakAlignGroup} @tab @code{Score} @tab calculated
3444 @item @code{BreathingSign} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3445 @item @code{Clef} @tab @code{Staff} @tab @code{begin-of-line-visible}
3446 @item @code{Custos} @tab @code{Staff} @tab @code{end-of-line-visible}
3447 @item @code{DoublePercentRepeat} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3448 @item @code{KeyCancellation} @tab @code{Staff} @tab @code{begin-of-line-invisible}
3449 @item @code{KeySignature} @tab @code{Staff} @tab @code{begin-of-line-visible}
3450 @c omit LeftEdge until it can be explained -td
3451 @c @item @code{LeftEdge} @tab @code{Score} @tab @code{center-invisible}
3452 @item @code{ClefModifier} @tab @code{Staff} @tab @code{begin-of-line-visible}
3453 @item @code{RehearsalMark} @tab @code{Score} @tab @code{end-of-line-invisible}
3454 @item @code{TimeSignature} @tab @code{Staff} @tab @code{all-visible}
3458 The example below shows the use of the vector form to control the
3459 visibility of bar lines:
3461 @lilypond[quote,verbatim,ragged-right]
3465 % Remove bar line at the end of the current line
3466 \once \override Score.BarLine.break-visibility = ##(#f #t #t)
3473 Although all three components of the vector used to override
3474 @code{break-visibility} must be present, not all of them are
3475 effective with every layout object, and some combinations may
3476 even give errors. The following limitations apply:
3479 @item Bar lines cannot be printed at the start of line.
3481 @item A bar number cannot be printed at the start of the @emph{first}
3482 line unless it is set to be different from @code{1}.
3484 @item Clef -- see the next section.
3486 @item Double percent repeats are either @emph{all printed} or
3487 @emph{all suppressed}. Use @code{begin-of-line-invisible}
3488 to print them and @code{all-invisible} to suppress them.
3490 @item Key signature -- see the next section.
3492 @item ClefModifier -- see the next section.
3496 @node Special considerations
3497 @unnumberedsubsubsec Special considerations
3499 @subsubsubheading Visibility following explicit changes
3501 @cindex key signature, visibility following explicit change
3502 @cindex explicitKeySignatureVisibility
3503 @cindex clef, visibility following explicit change
3504 @cindex explicitClefVisibility
3506 The @code{break-visibility} property controls the visibility of
3507 key signatures and changes of clef only at the start of lines,
3508 i.e., after a break. It has no effect on the visibility of the
3509 key signature or clef following an explicit key change or an
3510 explicit clef change within or at the end of a line. In the
3511 following example the key signature following the explicit change
3512 to B-flat major is still visible, even though @code{all-invisible}
3515 @lilypond[quote,verbatim,ragged-right]
3519 % Try to remove all key signatures
3520 \override Staff.KeySignature.break-visibility = #all-invisible
3529 The visibility of such explicit key signature and clef changes is
3530 controlled by the @code{explicitKeySignatureVisibility} and
3531 @code{explicitClefVisibility} properties. These are the equivalent
3532 of the @code{break-visibility} property and both take a vector of
3533 three booleans or the predefined functions listed above, exactly like
3534 @code{break-visibility}. Both are properties of the Staff context,
3535 not the layout objects themselves, and so they are set using the
3536 @code{\set} command. Both are set by default to @code{all-visible}.
3537 These properties control only the visibility of key signatures and
3538 clefs resulting from explicit changes and do not affect key
3539 signatures and clefs at the beginning of lines;
3540 @code{break-visibility} must still be overridden in the appropriate
3541 object to remove these.
3543 @lilypond[quote,verbatim,ragged-right]
3547 \set Staff.explicitKeySignatureVisibility = #all-invisible
3548 \override Staff.KeySignature.break-visibility = #all-invisible
3556 @subsubsubheading Visibility of cancelling accidentals
3558 To remove the cancelling accidentals printed at an explicit key
3559 change, set the Staff context property @code{printKeyCancellation}
3562 @lilypond[quote,verbatim,ragged-right]
3566 \set Staff.explicitKeySignatureVisibility = #all-invisible
3567 \set Staff.printKeyCancellation = ##f
3568 \override Staff.KeySignature.break-visibility = #all-invisible
3576 With these overrides only the accidentals before the notes remain
3577 to indicate the change of key.
3579 Note that when changing the key to C@tie{}major or A@tie{}minor
3580 the cancelling accidentals would be the @emph{only} indication of
3581 the key change. In this case setting @code{printKeyCancellation} to
3582 @code{#f} has no effect:
3584 @lilypond[quote,verbatim,ragged-right]
3588 \set Staff.explicitKeySignatureVisibility = #all-invisible
3589 \set Staff.printKeyCancellation = ##f
3597 To suppress the cancelling accidentals even when the key is
3598 changed to C@tie{}major or A@tie{}minor, override
3599 the visibility of the @code{KeyCancellation} grob instead:
3601 @lilypond[quote,verbatim,ragged-right]
3605 \set Staff.explicitKeySignatureVisibility = #all-invisible
3606 \override Staff.KeyCancellation.break-visibility = #all-invisible
3614 @c TODO Add visibility of cautionary accidentals before notes
3616 @subsubsubheading Automatic bars
3618 @cindex automaticBars
3619 @cindex bar lines, suppressing
3621 As a special case, the printing of bar lines can also be turned off
3622 by setting the @code{automaticBars} property in the Score context.
3623 If set to @code{#f}, bar lines will not be printed automatically;
3624 they must be explicitly created with a @code{\bar} command. Unlike
3625 the @code{\cadenzaOn} predefined command, measures are still counted.
3626 Bar generation will resume according to that count if this property
3627 is later set to @code{#t}. When set to @code{#f}, line breaks can
3628 occur only at explicit @code{\bar} commands.
3632 @subsubsubheading Transposed clefs
3634 @cindex transposed clefs, visibility of
3635 @cindex visibility of transposed clefs
3636 @cindex clefs, visibility of transposition
3638 The small transposition symbol on transposed clefs is produced by the
3639 @code{ClefModifier} layout object. Its visibility is automatically
3640 inherited from the @code{Clef} object, so it is not necessary to apply
3641 any required @code{break-visibility} overrides to the @code{ClefModifier}
3642 layout objects to suppress transposition symbols for invisible clefs.
3644 For explicit clef changes, the @code{explicitClefVisibility}
3645 property controls both the clef symbol and any transposition symbol
3650 @rlearning{Visibility and color of objects}.
3654 @subsection Line styles
3656 Some performance indications, e.g., @i{rallentando} and
3657 @i{accelerando} and @i{trills} are written as text and are
3658 extended over many measures with lines, sometimes dotted or wavy.
3660 These all use the same routines as the glissando for drawing the
3661 texts and the lines, and tuning their behavior is therefore also
3662 done in the same way. It is done with a spanner, and the routine
3663 responsible for drawing the spanners is
3664 @code{ly:line-spanner::print}. This routine determines the
3665 exact location of the two @i{span points} and draws a line
3666 between them, in the style requested.
3668 Here is an example showing the different line styles available,
3669 and how to tune them.
3671 @lilypond[ragged-right,verbatim,quote]
3674 \once \override Glissando.style = #'dashed-line
3676 \override Glissando.style = #'dotted-line
3678 \override Glissando.style = #'zigzag
3680 \override Glissando.style = #'trill
3685 The locations of the end-points of the spanner are computed
3686 on-the-fly for every graphic object, but it is possible to
3690 @lilypond[ragged-right,verbatim,quote]
3693 \once \override Glissando.bound-details.right.Y = #-2
3698 The value for @code{Y} is set to @w{@code{-2}} for the right end
3699 point. The left side may be similarly adjusted by specifying
3700 @code{left} instead of @code{right}.
3702 If @code{Y} is not set, the value is computed from the vertical
3703 position of the left and right attachment points of the spanner.
3705 Other adjustments of spanners are possible, for details, see
3708 @node Rotating objects
3709 @subsection Rotating objects
3711 Both layout objects and elements of markup text can be rotated by
3712 any angle about any point, but the method of doing so differs.
3715 * Rotating layout objects::
3719 @node Rotating layout objects
3720 @unnumberedsubsubsec Rotating layout objects
3722 @cindex rotating objects
3723 @cindex objects, rotating
3725 All layout objects which support the @code{grob-interface} can be
3726 rotated by setting their @code{rotation} property. This takes a
3727 list of three items: the angle of rotation counter-clockwise,
3728 and the x and y coordinates of the point relative to the object's
3729 reference point about which the rotation is to be performed. The
3730 angle of rotation is specified in degrees and the coordinates in
3733 The angle of rotation and the coordinates of the rotation point must
3734 be determined by trial and error.
3736 @cindex hairpins, angled
3737 @cindex angled hairpins
3739 There are only a few situations where the rotation of layout
3740 objects is useful; the following example shows one situation where
3743 @lilypond[quote,fragment,verbatim]
3745 \override Hairpin.rotation = #'(20 -1 0)
3749 @node Rotating markup
3750 @unnumberedsubsubsec Rotating markup
3752 All markup text can be rotated to lie at any angle by prefixing it
3753 with the @code{\rotate} command. The command takes two arguments:
3754 the angle of rotation in degrees counter-clockwise and the text to
3755 be rotated. The extents of the text are not rotated: they take
3756 their values from the extremes of the x and y coordinates of the
3757 rotated text. In the following example the
3758 @code{outside-staff-priority} property for text is set to @code{#f}
3759 to disable the automatic collision avoidance, which would push some
3760 of the text too high.
3762 @lilypond[quote,fragment,verbatim]
3763 \override TextScript.outside-staff-priority = ##f
3764 g4^\markup { \rotate #30 "a G" }
3765 b^\markup { \rotate #30 "a B" }
3766 des'^\markup { \rotate #30 "a D-Flat" }
3767 fis'^\markup { \rotate #30 "an F-Sharp" }
3770 @node Advanced tweaks
3771 @section Advanced tweaks
3773 This section discusses various approaches to fine tuning the
3774 appearance of the printed score.
3777 * Aligning objects::
3778 * Vertical grouping of grobs::
3779 * Modifying stencils::
3780 * Modifying shapes::
3781 * Modifying broken spanners::
3782 * Unpure-pure containers::
3787 @rlearning{Tweaking output},
3788 @rlearning{Other sources of information}.
3791 @ref{Explaining the Internals Reference},
3792 @ref{Modifying properties}.
3795 @rextend{Interfaces for programmers}.
3798 @file{scm/define-grobs.scm}.
3801 @rlsr{Tweaks and overrides}.
3803 Internals Reference:
3804 @rinternals{All layout objects}.
3807 @node Aligning objects
3808 @subsection Aligning objects
3810 Graphical objects which support the @code{self-alignment-interface}
3811 and/or the @code{side-position-interface} can be aligned to a previously
3812 placed object in a variety of ways. For a list of these objects, see
3813 @rinternals{self-alignment-interface} and @rinternals{side-position-interface}.
3815 All graphical objects have a reference point, a horizontal extent and a
3816 vertical extent. The horizontal extent is a pair of numbers
3817 giving the displacements from the reference point of the left and
3818 right edges, displacements to the left being negative. The vertical
3819 extent is a pair of numbers giving the displacement from the reference
3820 point to the bottom and top edges, displacements down being negative.
3822 An object's position on a staff is given by the values of the
3823 @code{X-offset} and @code{Y-offset} properties. The value of
3824 @code{X-offset} gives the displacement from the X coordinate of
3825 the reference point of the parent object, and the value of
3826 @code{Y-offset} gives the displacement from the center line of the
3827 staff. The values of @code{X-offset} and @code{Y-offset} may
3828 be set directly or may be set to be calculated by procedures in order
3829 to achieve alignment with the parent object.
3831 @warning{Many objects have special positioning considerations which
3832 cause any setting of @code{X-offset} or @code{Y-offset} to be
3833 ignored or modified, even though the object supports the
3834 @code{self-alignment-interface}. Overriding the @code{X-offset}
3835 or @code{Y-offset} properties to a fixed value causes the respective
3836 @code{self-alignment} property to be disregarded.}
3838 For example, an accidental can be repositioned vertically by setting
3839 @code{Y-offset} but any changes to @code{X-offset} have no effect.
3841 Rehearsal marks may be aligned with breakable objects such as bar
3842 lines, clef symbols, time signature symbols and key signatures. There
3843 are special properties to be found in the @code{break-aligned-interface}
3844 for positioning rehearsal marks on such objects.
3848 @ref{Using the break-alignable-interface}.
3851 @rextend{Callback functions}.
3854 * Setting X-offset and Y-offset directly::
3855 * Using the side-position-interface::
3856 * Using the self-alignment-interface::
3857 * Using the break-alignable-interface::
3860 @node Setting X-offset and Y-offset directly
3861 @unnumberedsubsubsec Setting @code{X-offset} and @code{Y-offset} directly
3863 Numerical values may be given to the @code{X-offset} and @code{Y-offset}
3864 properties of many objects. The following example shows three
3865 notes with the default fingering position and the positions with @code{X-offset}
3866 and @code{Y-offset} modified.
3868 @lilypond[verbatim,fragment,quote]
3875 -\tweak X-offset #-1
3882 @node Using the side-position-interface
3883 @unnumberedsubsubsec Using the @code{side-position-interface}
3885 An object which supports the @code{side-position-interface} can be
3886 placed next to its parent object so that
3887 the specified edges of the two objects touch. The object may be
3888 placed above, below, to the right or to the left of the parent.
3889 The parent cannot be specified; it is determined by the order of
3890 elements in the input stream. Most objects have the associated
3891 note head as their parent.
3893 The values of the @code{side-axis} and @code{direction} properties
3894 determine where the object is to be placed, as follows:
3896 @c TODO add an example of each to the table
3898 @multitable @columnfractions .3 .3 .3
3899 @headitem @code{side-axis} @tab @code{direction} @tab
3900 @headitem property @tab property @tab Placement
3902 @item @code{0} @tab @code{-1} @tab left
3903 @item @code{0} @tab @code{1} @tab right
3904 @item @code{1} @tab @code{-1} @tab below
3905 @item @code{1} @tab @code{1} @tab above
3909 When @code{side-axis} is @code{0}, @code{X-offset} should be set to
3910 the procedure @code{ly:side-position-interface::x-aligned-side}.
3911 This procedure will return the correct value of @code{X-offset} to
3912 place the object to the left or right side of the parent according
3913 to value of @code{direction}.
3915 When @code{side-axis} is @code{1}, @code{Y-offset} should be set to
3916 the procedure @code{ly:side-position-interface::y-aligned-side}.
3917 This procedure will return the correct value of @code{Y-offset} to
3918 place the object to the top or bottom of the parent according
3919 to value of @code{direction}.
3921 @c TODO Add examples
3923 @node Using the self-alignment-interface
3924 @unnumberedsubsubsec Using the @code{self-alignment-interface}
3926 @subsubsubheading Self-aligning objects horizontally
3928 The horizontal alignment of an object which supports the
3929 @code{self-alignment-interface} is controlled by the value of
3930 the @code{self-alignment-X} property, provided the object's
3931 @code{X-offset} property is set to
3932 @code{ly:self-alignment-interface::x-aligned-on-self}.
3933 @code{self-alignment-X} may be given any
3934 real value, in units of half the total X extent of the
3935 object. Negative values move the object to the right, positive
3936 to the left. A value of @code{0} centers the object on the
3937 reference point of its parent, a value of @w{@code{-1}} aligns the
3938 left edge of the object on the reference point of its parent,
3939 and a value of @code{1} aligns the right edge of the object on the
3940 reference point of its parent. The symbols @code{LEFT},
3941 @code{CENTER}, and @code{RIGHT} may be used instead of the values
3942 @w{@code{-1}}, @code{0}, and @code{1}, respectively.
3944 Normally the @code{\override} command would be used to modify the
3945 value of @code{self-alignment-X}, but the @code{\tweak} command
3946 can be used to separately align several annotations on a single
3949 @lilypond[quote,verbatim,fragment]
3951 -\tweak self-alignment-X #-1
3953 -\tweak self-alignment-X #0
3955 -\tweak self-alignment-X #RIGHT
3957 -\tweak self-alignment-X #-2.5
3958 ^"aligned further to the right"
3961 @subsubsubheading Self-aligning objects vertically
3963 Objects may be aligned vertically in an analogous way to aligning
3964 them horizontally if the @code{Y-offset} property is set to
3965 @code{ly:self-alignment-interface::y-aligned-on-self}. However,
3966 other mechanisms are often involved in vertical alignment: the
3967 value of @code{Y-offset} is just one variable taken into account.
3968 This may make adjusting the value of some objects tricky.
3969 The units are just half the vertical extent of the object, which
3970 is usually quite small, so quite large numbers may be required.
3971 A value of @w{@code{-1}} aligns the lower edge of the object with
3972 the reference point of the parent object, a value of @code{0}
3973 aligns the center of the object with the reference point of the
3974 parent, and a value of @code{1} aligns the top edge of the object
3975 with the reference point of the parent. The symbols @code{DOWN},
3976 @code{CENTER}, and @code{UP} may be substituted for @w{@code{-1}},
3977 @code{0}, and @code{1}, respectively.
3979 @subsubsubheading Self-aligning objects in both directions
3981 By setting both @code{X-offset} and @code{Y-offset}, an object may
3982 be aligned in both directions simultaneously.
3984 The following example shows how to adjust a fingering mark so
3985 that it nestles close to the note head.
3987 @lilypond[quote,verbatim,fragment]
3989 -\tweak self-alignment-X #0.5 % move horizontally left
3990 -\tweak Y-offset #ly:self-alignment-interface::y-aligned-on-self
3991 -\tweak self-alignment-Y #-1 % move vertically up
3996 @unnumberedsubsubsec Using the @code{aligned-on-parent} procedures
3998 @c Cannot document as they do not seem to operate consistently on all objects -td
3999 @c TODO investigate further
4001 The @code{aligned-on-parent} procedures are used in the same way
4002 as the @code{aligned-on-self} procedures, they difference being
4003 that they permit an object to be aligned with the @emph{edges} of
4004 the parent rather than the parent's reference point. The following
4005 example shows the difference:
4009 @lilypond[verbatim,quote]
4015 @unnumberedsubsubsec Using the @code{centered-on-parent} procedures
4017 @c Cannot document as they do not seem to operate consistently on all objects -td
4018 @c TODO investigate further
4022 @c TODO The align-interface, BassFigureAlignment and VerticalAlignment
4024 @node Using the break-alignable-interface
4025 @unnumberedsubsubsec Using the @code{break-alignable-interface}
4027 @cindex align to objects
4028 @cindex break-align-symbols
4030 Rehearsal marks and bar numbers may be aligned with notation
4031 objects other than bar lines. These objects include @code{ambitus},
4032 @code{breathing-sign}, @code{clef}, @code{custos}, @code{staff-bar},
4033 @code{left-edge}, @code{key-cancellation}, @code{key-signature}, and
4034 @code{time-signature}.
4036 Each type of object has its own default reference point, to which
4037 rehearsal marks are aligned:
4039 @lilypond[verbatim,quote,fragment]
4040 % The rehearsal mark will be aligned to the right edge of the Clef
4041 \override Score.RehearsalMark.break-align-symbols = #'(clef)
4046 % The rehearsal mark will be aligned to the left edge of the Time Signature
4047 \override Score.RehearsalMark.break-align-symbols = #'(time-signature)
4053 % The rehearsal mark will be centered above the Breath Mark
4054 \override Score.RehearsalMark.break-align-symbols = #'(breathing-sign)
4063 A list of possible target alignment objects may be specified. If
4064 some of the objects are invisible at that point due to the setting
4065 of @code{break-visibility} or the explicit visibility settings for
4066 keys and clefs, the rehearsal mark or bar number is aligned to the
4067 first object in the list which is visible. If no objects in the
4068 list are visible the object is aligned to the bar line. If the bar
4069 line is invisible the object is aligned to the place where the bar
4072 @lilypond[verbatim,quote,fragment]
4073 % The rehearsal mark will be aligned to the right edge of the Key Signature
4074 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4079 % The rehearsal mark will be aligned to the right edge of the Clef
4080 \set Staff.explicitKeySignatureVisibility = #all-invisible
4081 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4086 % The rehearsal mark will be centered above the Bar Line
4087 \set Staff.explicitKeySignatureVisibility = #all-invisible
4088 \set Staff.explicitClefVisibility = #all-invisible
4089 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4096 The alignment of the rehearsal mark relative to the notation object
4097 can be changed, as shown in the following example. In a score with
4098 multiple staves, this setting should be done for all the staves.
4100 @lilypond[verbatim,quote,fragment]
4101 % The RehearsalMark will be aligned with the right edge of the Key Signature
4102 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4108 % The RehearsalMark will be centered above the Key Signature
4109 \once \override Score.KeySignature.break-align-anchor-alignment = #CENTER
4113 % The RehearsalMark will be aligned with the left edge of the Key Signature
4114 \once \override Score.KeySignature.break-align-anchor-alignment = #LEFT
4120 The rehearsal mark can also be offset to the right or left of the left
4121 edge by an arbitrary amount. The units are staff-spaces:
4123 @lilypond[verbatim,quote,fragment]
4124 % The RehearsalMark will be aligned with the left edge of the Key Signature
4125 % and then shifted right by 3.5 staff-spaces
4126 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4127 \once \override Score.KeySignature.break-align-anchor = #3.5
4131 % The RehearsalMark will be aligned with the left edge of the Key Signature
4132 % and then shifted left by 2 staff-spaces
4133 \once \override Score.KeySignature.break-align-anchor = #-2
4140 @node Vertical grouping of grobs
4141 @subsection Vertical grouping of grobs
4143 @c TODO Expand this section
4145 The VerticalAlignment and VerticalAxisGroup grobs work together.
4146 VerticalAxisGroup groups together different grobs like Staff, Lyrics,
4147 etc. VerticalAlignment then vertically aligns the different grobs
4148 grouped together by VerticalAxisGroup. There is usually only one
4149 VerticalAlignment per score but every Staff, Lyrics, etc., has its own
4153 @node Modifying stencils
4154 @subsection Modifying stencils
4156 All layout objects have a @code{stencil} property which is part of
4157 the @code{grob-interface}. By default, this property is usually
4158 set to a function specific to the object that is tailor-made to
4159 render the symbol which represents it in the output. For example,
4160 the standard setting for the @code{stencil} property of the
4161 @code{MultiMeasureRest} object is @code{ly:multi-measure-rest::print}.
4163 The standard symbol for any object can be replaced by modifying the
4164 @code{stencil} property to reference a different, specially-written,
4165 procedure. This requires a high level of knowledge of the internal
4166 workings of LilyPond, but there is an easier way which can often
4167 produce adequate results.
4169 This is to set the @code{stencil} property to the procedure which
4170 prints text -- @code{ly:text-interface::print} -- and to add a
4171 @code{text} property to the object which is set to contain the
4172 markup text which produces the required symbol. Due to the
4173 flexibility of markup, much can be achieved -- see in particular
4174 @ref{Graphic notation inside markup}.
4176 The following example demonstrates this by changing the note head
4177 symbol to a cross within a circle.
4179 @lilypond[verbatim,quote]
4181 \once \override NoteHead.stencil = #ly:text-interface::print
4182 \once \override NoteHead.text = \markup {
4184 \halign #-0.7 \draw-circle #0.85 #0.2 ##f
4185 \musicglyph #"noteheads.s2cross"
4193 Any of the glyphs in the Feta Font can be supplied to the
4194 @code{\musicglyph} markup command -- see @ref{The Feta font}.
4196 @file{EPS} files and Postscript commands can both be inserted inline
4197 using the @code{\epsfile} and @code{\postscript} markup commands
4198 respectively -- see @ref{Graphic}.
4203 @ref{Graphic notation inside markup},
4204 @ref{Formatting text},
4205 @ref{Text markup commands},
4206 @ref{The Feta font},
4210 @node Modifying shapes
4211 @subsection Modifying shapes
4214 * Modifying ties and slurs::
4217 @node Modifying ties and slurs
4218 @unnumberedsubsubsec Modifying ties and slurs
4220 @cindex slurs, modifying
4221 @cindex ties, modifying
4222 @cindex Bézier curves, control points
4223 @cindex control points, Bézier curves
4225 @code{Tie}s, @code{Slur}s, @code{PhrasingSlur}s,
4226 @code{LaissezVibrerTie}s and @code{RepeatTie}s are all drawn as
4227 third-order Bézier curves. If the shape of the tie or slur which
4228 is calculated automatically is not optimum, the shape may be
4229 modified manually in two ways:
4233 by specifying the displacements to be made to the control points
4234 of the automatically calculated Bézier curve, or
4237 by explicitly specifying the positions of the four control points
4238 required to define the wanted curve.
4241 Both methods are explained below. The first method is more suitable
4242 if only slight adjustments to the curve are required; the second may
4243 be better for creating curves which are related to just a single
4246 @subsubsubheading Cubic Bézier curves
4248 Third-order or cubic Bézier curves are defined by four control
4249 points. The first and fourth control points are precisely the
4250 starting and ending points of the curve. The intermediate two
4251 control points define the shape. Animations showing how the curve
4252 is drawn can be found on the web, but the following description
4253 may be helpful. The curve starts from the first control point
4254 heading directly towards the second, gradually bending over to
4255 head towards the third and continuing to bend over to head towards
4256 the fourth, arriving there travelling directly from the third
4257 control point. The curve is entirely contained in the
4258 quadrilateral defined by the four control points. Translations,
4259 rotations and scaling of the control points all result in exactly
4260 the same operations on the curve.
4262 @subsubsubheading Specifying displacements from current control points
4264 @cindex shaping slurs and ties
4267 In this example the automatic placement of the tie is not optimum,
4268 and @code{\tieDown} would not help.
4270 @lilypond[verbatim,quote]
4274 \relative { r4 <g' c,> <g c,> <g c,> }
4278 Adjusting the control points of the tie with @code{\shape} allows
4279 the collisions to be avoided.
4281 The syntax of @code{\shape} is
4284 [-]\shape @var{displacements} @var{item}
4287 This will reposition the control-points of @var{item} by the amounts
4288 given by @var{displacements}. The @var{displacements} argument is a
4289 list of number pairs or a list of such lists. Each element of a pair
4290 represents the displacement of one of the coordinates of a
4291 control-point. If @var{item} is a string, the result is
4292 @code{\once\override} for the specified grob type. If @var{item} is
4293 a music expression, the result is the same music expression with an
4294 appropriate tweak applied.
4296 In other words, the @code{\shape} function can act as either a
4297 @code{\once\override} command or a @code{\tweak} command depending
4298 on whether the @var{item} argument is a grob name, like @qq{Slur},
4299 or a music expression, like @qq{(}. The @var{displacements} argument
4300 specifies the displacements of the four control points as a list of
4301 four pairs of (dx . dy) values in units of staff-spaces (or a list
4302 of such lists if the curve has more than one segment).
4304 The leading hyphen is required if and only if the @code{\tweak} form
4307 So, using the same example as above and the @code{\once\override}
4308 form of @code{\shape}, this will raise the tie by half a staff-space:
4310 @lilypond[verbatim,quote]
4313 \shape #'((0 . 0.5) (0 . 0.5) (0 . 0.5) (0 . 0.5)) Tie
4317 \relative { r4 <g' c,> <g c,> <g c,> }
4321 This positioning of the tie is better, but maybe it should be raised
4322 more in the center. The following example does this, this time using
4323 the alternative @code{\tweak} form:
4325 @lilypond[verbatim,quote]
4328 e'1-\shape #'((0 . 0.5) (0 . 1) (0 . 1) (0 . 0.5)) ~ e'
4331 \relative { r4 <g' c,> <g c,> <g c,> }
4335 Changes to the horizontal positions of the control points may be made
4336 in the same way, and two different curves starting at the same
4337 musical moment may also be shaped:
4339 @lilypond[verbatim,quote,ragged-right]
4341 c''8(\( a) a'4 e c\)
4342 \shape #'((0.7 . -0.4) (0.5 . -0.4) (0.3 . -0.3) (0 . -0.2)) Slur
4343 \shape #'((0 . 0) (0 . 0.5) (0 . 0.5) (0 . 0)) PhrasingSlur
4348 The @code{\shape} function can also displace the control points of
4349 curves which stretch across line breaks. Each piece of the broken
4350 curve can be given its own list of offsets. If changes to a
4351 particular segment are not needed, the empty list can serve as a
4352 placeholder. In this example the line break makes the single slur
4355 @lilypond[verbatim,quote,ragged-right]
4363 Changing the shapes of the two halves of the slur makes it clearer
4364 that the slur continues over the line break:
4366 @lilypond[verbatim,quote,ragged-right]
4367 % () may be used as a shorthand for ((0 . 0) (0 . 0) (0 . 0) (0 . 0))
4368 % if any of the segments does not need to be changed
4371 (( 0 . 0) (0 . 0) (0 . 0) (0 . 1))
4372 ((0.5 . 1.5) (1 . 0) (0 . 0) (0 . -1.5))
4380 If an S-shaped curve is required the control points must always be
4381 adjusted manually --- LilyPond will never select such shapes
4384 @lilypond[verbatim,quote]
4386 c8( e b-> f d' a e-> g)
4387 \shape #'((0 . -1) (5.5 . -0.5) (-5.5 . -10.5) (0 . -5.5)) PhrasingSlur
4388 c8\( e b-> f d' a e-> g\)
4392 @subsubsubheading Specifying control points explicitly
4394 The coordinates of the Bézier control points are specified in units
4395 of staff-spaces. The X@tie{}coordinate is relative to the reference
4396 point of the note to which the tie or slur is attached, and the
4397 Y@tie{}coordinate is relative to the staff center line. The
4398 coordinates are specified as a list of four pairs of decimal numbers
4399 (reals). One approach is to estimate the coordinates of the two
4400 end points, and then guess the two intermediate points. The optimum
4401 values are then found by trial and error. Be aware that these values
4402 may need to be manually adjusted if any further changes are made to
4403 the music or the layout.
4405 One situation where specifying the control points explicitly is
4406 preferable to specifying displacements is when they need to be
4407 specified relative to a single note. Here is an example of this.
4408 It shows one way of indicating a slur extending into alternative
4409 sections of a volta repeat.
4411 @lilypond[verbatim,quote]
4414 \repeat volta 3 { c4 d( e f }
4419 % create a slur and move it to a new position
4420 % the <> is just an empty chord to carry the slur termination
4421 -\tweak control-points #'((-2 . 3.8) (-1 . 3.9) (0 . 4) (1 . 3.4)) ( <> )
4426 % create a slur and move it to a new position
4427 -\tweak control-points #'((-2 . 3) (-1 . 3.1) (0 . 3.2) (1 . 2.4)) ( <> )
4435 It is not possible to modify shapes of ties or slurs by changing
4436 the @code{control-points} property if there are multiple ties or slurs
4437 at the same musical moment -- the @code{\tweak} command will also not
4438 work in this case. However, the @code{tie-configuration} property of
4439 @code{TieColumn} can be overridden to set start line and direction as
4443 Internals Reference:
4444 @rinternals{TieColumn}.
4447 @node Modifying broken spanners
4448 @subsection Modifying broken spanners
4451 * Using alterBroken::
4454 @node Using alterBroken
4455 @unnumberedsubsubsec Using @code{\alterBroken}
4457 @cindex spanners, modifying
4458 @cindex broken spanners, modifying
4459 @funindex \alterBroken
4461 When a spanner crosses a line break or breaks, each piece
4462 inherits the attributes of the original spanner. Thus, ordinary
4463 tweaking of a broken spanner applies the same modifications to
4464 each of its segments. In the example below, overriding
4465 @code{thickness} affects the slur on either side of the line
4468 @lilypond[verbatim,quote,ragged-right]
4471 \once\override Slur.thickness = 10
4478 Independently modifying the appearance of individual pieces
4479 of a broken spanner is possible with the @code{\alterBroken}
4480 command. This command can produce either an @code{\override}
4481 or a @code{\tweak} of a spanner property.
4483 The syntax for @code{\alterBroken} is
4486 [-]\alterBroken @var{property} @var{values} @var{item}
4489 The argument @var{values} is a list of values, one for each
4490 broken piece. If @var{item} is a grob name like @code{Slur} or
4491 @code{Staff.PianoPedalBracket}, the result is an @code{\override}
4492 of the specified grob type. If @var{item} is a music expression
4493 such as @qq{(} or @qq{[} the result is the same music expression
4494 with an appropriate tweak applied.
4496 The leading hyphen must be used with the @code{\tweak} form. Do
4497 not add it when @code{\alterBroken} is used as an
4500 In its @code{\override} usage, @code{\alterBroken} may be
4501 prefaced by @code{\once} or @code{\temporary} and reverted by
4502 using @code{\revert} with @var{property}.
4504 The following code applies an independent @code{\override} to
4505 each of the slur segments in the previous example:
4507 @lilypond[verbatim,quote,ragged-right]
4510 \alterBroken thickness #'(10 1) Slur
4517 The @code{\alterBroken} command may be used with any spanner
4518 object, including @code{Tie}, @code{PhrasingSlur}, @code{Beam}
4519 and @code{TextSpanner}. For example, an editor preparing a
4520 scholarly edition may wish to indicate the absence of part of a
4521 phrasing slur in a source by dashing only the segment which has
4522 been added. The following example illustrates how this can be
4523 done, in this case using the @code{\tweak} form of the command:
4525 @lilypond[verbatim,quote,ragged-right]
4526 % The empty list is conveniently used below, because it is the
4527 % default setting of dash-definition, resulting in a solid curve.
4529 c''2-\alterBroken dash-definition #'(() ((0 1.0 0.4 0.75))) \(e
4535 It is important to understand that @code{\alterBroken} will set
4536 each piece of a broken spanner to the corresponding value in
4537 @var{values}. When there are fewer values than pieces, any
4538 additional piece will be assigned the empty list. This may lead
4539 to undesired results if the layout property is not set to the
4540 empty list by default. In such cases, each segment should be
4541 assigned an appropriate value.
4544 Line breaks may occur in different places following changes in
4545 layout. Settings chosen for @code{\alterBroken} may be unsuitable
4546 for a spanner that is no longer broken or is split into more
4547 segments than before. Explicit use of @code{\break} can guard
4548 against this situation.
4550 The @code{\alterBroken} command is ineffective for spanner
4551 properties accessed before line-breaking such as
4556 @rextend{Difficult tweaks}.
4559 @node Unpure-pure containers
4560 @subsection Unpure-pure containers
4562 @cindex Scheme, pure containers
4563 @cindex Scheme, unpure containers
4564 @cindex pure containers, Scheme
4565 @cindex unpure containers, Scheme
4566 @cindex horizontal spacing, overriding
4568 Unpure-pure containers are useful for overriding @emph{Y-axis} spacing
4569 calculations - specifically @code{Y-offset} and @code{Y-extent} - with a
4570 Scheme function instead of a literal (i.e., a number or pair).
4572 For certain grobs, the @code{Y-extent} is based on the @code{stencil}
4573 property, overriding the stencil property of one of these will
4574 require an additional @code{Y-extent} override with an unpure-pure
4575 container. When a function overrides a @code{Y-offset} and/or
4576 @code{Y-extent} it is assumed that this will trigger line breaking
4577 calculations too early during compilation. So the function is not
4578 evaluated at all (usually returning a value of @samp{0} or
4579 @samp{'(0 . 0)}) which can result in collisions. A @q{pure} function
4580 will not affect properties, objects or grob suicides and therefore will
4581 always have its Y-axis-related evaluated correctly.
4583 Currently, there are about thirty functions that are already considered
4584 @q{pure} and Unpure-pure containers are a way to set functions not on
4585 this list as @q{pure}. The @q{pure} function is evaluated @emph{before}
4586 any line-breaking and so the horizontal spacing can be adjusted
4587 @q{in time}. The @q{unpure} function is then evaluated @emph{after}
4590 @warning{As it is difficult to always know which functions are on this
4591 list we recommend that any @q{pure} functions you create do not use
4592 @code{Beam} or @code{VerticalAlignment} grobs.}
4594 An unpure-pure container is constructed as follows;
4596 @code{(ly:make-unpure-pure-container f0 f1)}
4598 where @code{f0} is a function taking @var{n} arguments (@var{n >= 1})
4599 and the first argument must always be the grob. This is the function
4600 that gives the actual result. @var{f1} is the function being labeled
4601 as @q{pure} that takes @var{n + 2} arguments. Again, the first argument
4602 must always still be the grob but the second and third are @q{start}
4603 and @q{end} arguments.
4605 @var{start} and @var{end} are, for all intents and purposes, dummy
4606 values that only matter for @code{Spanners} (i.e @code{Hairpin} or
4607 @code{Beam}), that can return different height estimations based on a
4608 starting and ending column.
4610 The rest are the other arguments to the first function (which
4611 may be none if @var{n = 1}).
4613 The results of the second function are used as an approximation of the
4614 value needed which is then used by the first function to get the real
4615 value which is then used for fine-tuning much later during the spacing
4618 @c TODO: The following example supposedly showing a collision no longer
4619 @c 'works' since 2.18.x. Another example of a collision is needed.
4622 @lilypond[verbatim,quote,ragged-right]
4623 #(define (square-line-circle-space grob)
4624 (let* ((pitch (ly:event-property (ly:grob-property grob 'cause) 'pitch))
4625 (notename (ly:pitch-notename pitch)))
4626 (if (= 0 (modulo notename 2))
4627 (make-circle-stencil 0.5 0.0 #t)
4628 (make-filled-box-stencil '(0 . 1.0)
4631 squareLineCircleSpace = {
4632 \override NoteHead.stencil = #square-line-circle-space
4635 smartSquareLineCircleSpace = {
4636 \squareLineCircleSpace
4637 \override NoteHead.Y-extent =
4638 #(ly:make-unpure-pure-container
4639 ly:grob::stencil-height
4640 (lambda (grob start end) (ly:grob::stencil-height grob)))
4643 \new Voice \with { \remove "Stem_engraver" }
4645 \squareLineCircleSpace
4647 \smartSquareLineCircleSpace
4652 In the first measure, without the unpure-pure container, the spacing
4653 engine does not know the width of the note head and lets it collide with
4654 the accidentals. In the second measure, with unpure-pure containers,
4655 the spacing engine knows the width of the note heads and avoids the
4656 collision by lengthening the line accordingly.
4658 Usually for simple calculations nearly-identical functions for
4659 both the @q{unpure} and @q{pure} parts can be used, by only
4660 changing the number of arguments passed to, and the scope of, the
4661 function. This use case is frequent enough that
4662 @code{ly:make-unpure-pure-container} constructs such a second
4663 function by default when called with only one function argument.
4665 @warning{If a function is labeled as @q{pure} and it turns out not to
4666 be, the results can be unexpected.}
4669 @node Using music functions
4670 @section Using music functions
4672 @c TODO -- add @seealso, etc. to these subsections
4674 Where tweaks need to be reused with different music expressions,
4675 it is often convenient to make the tweak part of a @emph{music
4676 function}. In this section, we discuss only @emph{substitution}
4677 functions, where the object is to substitute a variable into a
4678 piece of LilyPond input code. Other more complex functions are
4679 described in @rextend{Music functions}.
4682 * Substitution function syntax::
4683 * Substitution function examples::
4686 @node Substitution function syntax
4687 @subsection Substitution function syntax
4689 Making a function that substitutes a variable into LilyPond
4690 code is easy. The general form of these functions is
4694 #(define-music-function
4695 (@var{arg1} @var{arg2} @dots{})
4696 (@var{type1?} @var{type2?} @dots{})
4698 @var{@dots{}music@dots{}}
4705 @multitable @columnfractions .33 .66
4706 @item @code{@var{argN}}
4707 @tab @var{n}th argument
4709 @item @code{@var{typeN?}}
4710 @tab a scheme @emph{type predicate} for which @code{@var{argN}}
4711 must return @code{#t}.
4713 @item @code{@var{@dots{}music@dots{}}}
4714 @tab normal LilyPond input, using @code{$} (in places where only
4715 Lilypond constructs are allowed) or @code{#} (to use it as a Scheme
4716 value or music function argument or music inside of music lists) to
4721 The list of type predicates is required. Some of the most common
4722 type predicates used in music functions are:
4726 cheap-list? @emph{(use instead of }@q{list?}@emph{ for faster processing)}
4738 For a list of available type predicates, see
4739 @ref{Predefined type predicates}. User-defined type predicates
4744 @ref{Predefined type predicates}.
4747 @rextend{Music functions}.
4750 @file{lily/music-scheme.cc},
4752 @file{scm/lily.scm}.
4755 @node Substitution function examples
4756 @subsection Substitution function examples
4758 This section introduces some substitution function examples.
4759 These are not intended to be exhaustive, but rather to demonstrate
4760 some of the possibilities of simple substitution functions.
4762 In the first example, a function is defined that simplifies
4763 setting the padding of a TextScript:
4765 @lilypond[quote,verbatim,ragged-right]
4767 #(define-music-function
4771 \once \override TextScript.padding = #padding
4775 c''4^"piu mosso" b a b
4777 c4^"piu mosso" b a b
4779 c4^"piu mosso" b a b
4783 In addition to numbers, we can use music expressions such
4784 as notes for arguments to music functions:
4786 @lilypond[quote,verbatim,ragged-right]
4788 #(define-music-function
4792 \tweak NoteHead.stencil #ly:text-interface::print
4793 \tweak NoteHead.text
4794 \markup \musicglyph #"custodes.mensural.u0"
4795 \tweak Stem.stencil ##f
4799 \relative { c'4 d e f \custosNote g }
4803 Both of those functions are simple single expressions where only
4804 the last element of a function call or override is missing. For
4805 those particular function definitions, there is a simpler
4806 alternative syntax, namely just writing out the constant part of
4807 the expression and replacing its final missing element with
4810 @lilypond[quote,verbatim,ragged-right]
4812 \once \override TextScript.padding = \etc
4815 c''4^"piu mosso" b a b
4817 c4^"piu mosso" b a b
4819 c4^"piu mosso" b a b
4823 @lilypond[quote,verbatim,ragged-right]
4825 \tweak NoteHead.stencil #ly:text-interface::print
4826 \tweak NoteHead.text
4827 \markup \musicglyph #"custodes.mensural.u0"
4828 \tweak Stem.stencil ##f
4831 \relative { c'4 d e f \custosNote g }
4835 Substitution functions with multiple arguments can be defined:
4837 @lilypond[quote,verbatim,ragged-right]
4839 #(define-music-function
4843 \once \override Score.MetronomeMark.padding = #padding
4844 \tempo \markup { \bold #tempotext }
4848 \tempo \markup { "Low tempo" }
4850 \tempoPadded #4.0 "High tempo"
4855 @c TODO: add appropriate @@ref's here.