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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
95 I knew it would... And leaving out some of them is perfectly fine
97 I do think that a list like this, with the main contexts and a
99 description of what they do (perhaps also with a note about what
101 behavior is associated with each of them, but this may be
103 should be there, and then we could simply list the remaining ones
105 further explanation and with links to the IR.
108 @c TODO Improve layout, order and consistency of wording -td
110 @c TODO Add introduction which explains contexts in generality -td
112 @c TODO Describe propagation of property values -td
114 Contexts are arranged hierarchically:
117 * Output definitions - blueprints for contexts::
118 * Score - the master of all contexts::
119 * Top-level contexts - staff containers::
120 * Intermediate-level contexts - staves::
121 * Bottom-level contexts - voices::
124 @node Output definitions - blueprints for contexts
125 @unnumberedsubsubsec Output definitions - blueprints for contexts
127 This section explains the relevance of output definitions when
128 working with contexts. Examples for actual output definitions are
129 given later (see @ref{Changing all contexts of the same type}).
131 @cindex output definitions
133 While music written in a file may refer to context types and
134 names, contexts are created only when the music is actually being
135 interpreted. LilyPond interprets music under control of an
136 @q{output definition} and may do so for several different output
137 definitions, resulting in different output. The output definition
138 relevant for printing music is specified using @code{\layout}.
141 A much simpler output definition used for producing Midi output is
142 specified using @code{\midi}. Several other output definitions
143 are used by LilyPond internally, like when using the part combiner
144 (@ref{Automatic part combining}) or creating music quotes
145 (@ref{Quoting other voices}).
147 Output definitions define the relation between contexts as well as
148 their respective default settings. While most changes will
149 usually be made inside of a @code{\layout} block, Midi-related
150 settings will only have an effect when made within a @code{\midi}
153 @funindex autoBeaming
154 Some settings affect several outputs: for example, if
155 @code{autoBeaming} is turned off in some context, beams count as
156 melismata for the purpose of matching music to lyrics as described
157 in @ref{Automatic syllable durations}. This matching is done both
158 for printed output as well as for Midi. If changes made to
159 @code{autoBeaming} within a context definition of a @code{\layout}
160 block are not repeated in the corresponding @code{\midi} block,
161 lyrics and music will get out of sync in Midi.
165 @file{ly/engraver-init.ly}.
166 @file{ly/performer-init.ly}.
168 @node Score - the master of all contexts
169 @unnumberedsubsubsec Score - the master of all contexts
171 This is the top level notation context. No other context can
172 contain a Score context. By default the Score context handles
173 the administration of time signatures and makes sure that items
174 such as clefs, time signatures, and key-signatures are aligned
177 A Score context is instantiated implicitly when a
178 @code{\score @{@dots{}@}} block is processed.
180 @node Top-level contexts - staff containers
181 @unnumberedsubsubsec Top-level contexts - staff containers
183 @strong{@emph{StaffGroup}}
185 Groups staves while adding a bracket on the left side, grouping
186 the staves together. The bar lines of the contained staves are
187 connected vertically. @code{StaffGroup} only consists of a collection
188 of staves, with a bracket in front and spanning bar lines.
190 @strong{@emph{ChoirStaff}}
192 Identical to @code{StaffGroup} except that the bar lines of the
193 contained staves are not connected vertically.
195 @strong{@emph{GrandStaff}}
197 A group of staves, with a brace on the left side, grouping the
198 staves together. The bar lines of the contained staves are
199 connected vertically.
201 @strong{@emph{PianoStaff}}
203 Just like @code{GrandStaff}, but with support for instrument names
204 to the left of each system.
206 @node Intermediate-level contexts - staves
207 @unnumberedsubsubsec Intermediate-level contexts - staves
209 @strong{@emph{Staff}}
211 Handles clefs, bar lines, keys, accidentals. It can contain
212 @code{Voice} contexts.
214 @strong{@emph{RhythmicStaff}}
216 Like @code{Staff} but for printing rhythms. Pitches are ignored
217 when engraving; the notes are printed on one line. The MIDI
218 rendition retains pitches unchanged.
220 @strong{@emph{TabStaff}}
222 Context for generating tablature. By default lays the music
223 expression out as a guitar tablature, printed on six lines.
225 @strong{@emph{DrumStaff}}
227 Handles typesetting for percussion. Can contain @code{DrumVoice}
229 @strong{@emph{VaticanaStaff}}
231 Same as @code{Staff}, except that it is designed for typesetting
232 a piece in gregorian style.
234 @strong{@emph{MensuralStaff}}
236 Same as @code{Staff}, except that it is designed for typesetting
237 a piece in mensural style.
239 @node Bottom-level contexts - voices
240 @unnumberedsubsubsec Bottom-level contexts - voices
242 Voice-level contexts initialise certain properties and start
243 appropriate engravers. A bottom-level context is one without
244 @code{defaultchild}. While it is possible to let it
245 accept/@/contain subcontexts, they can only be created and entered
248 @strong{@emph{Voice}}
250 Corresponds to a voice on a staff. This context handles the
251 conversion of dynamic signs, stems, beams, super- and sub-scripts,
252 slurs, ties, and rests. You have to instantiate this explicitly
253 if you require multiple voices on the same staff.
255 @strong{@emph{VaticanaVoice}}
257 Same as @code{Voice}, except that it is designed for typesetting
258 a piece in gregorian style.
260 @strong{@emph{MensuralVoice}}
262 Same as @code{Voice}, with modifications for typesetting a piece in
265 @strong{@emph{Lyrics}}
267 Corresponds to a voice with lyrics. Handles the printing of a
268 single line of lyrics.
270 @strong{@emph{DrumVoice}}
272 The voice context used in a percussion staff.
274 @strong{@emph{FiguredBass}}
276 The context in which @code{BassFigure} objects are created from
277 input entered in @code{\figuremode} mode.
279 @strong{@emph{TabVoice}}
281 The voice context used within a @code{TabStaff} context. Usually
282 left to be created implicitly.
284 @strong{@emph{CueVoice}}
286 A voice context used to render notes of a reduced size, intended
287 primarily for adding cue notes to a staff, see @ref{Formatting
288 cue notes}. Usually left to be created implicitly.
290 @strong{@emph{ChordNames}}
292 Typesets chord names.
297 Then the following, which I don't know what to do with:
299 * GregorianTranscriptionVoice
300 * GregorianTranscriptionStaff
303 Engraves fretboards from chords. Not easy... Not
305 There is now some documentation on FretBoards in the NR, under
306 instrument-specific notation -- cds.
311 Hard coded entry point for LilyPond. Cannot be tuned.
313 Silently discards all musical information given to this
318 @node Creating and referencing contexts
319 @subsection Creating and referencing contexts
324 @cindex referencing contexts
325 @cindex Contexts, creating and referencing
327 LilyPond will create lower-level contexts automatically if a music
328 expression is encountered before a suitable context exists, but this
329 is usually successful only for simple scores or music fragments like
330 the ones in the documentation. For more complex scores it is
331 advisable to specify all contexts explicitly with either the
332 @code{\new} or @code{\context} command. The syntax of
333 these two commands is very similar:
336 [\new | \context] @var{Context} [ = @var{name}] [@var{music-expression}]
340 where either @code{\new} or @code{\context} may be specified.
341 @var{Context} is the type of context which is to be created,
342 @var{name} is an optional name to be given to the particular context
343 being created and @var{music-expression} is a single music expression
344 that is to be interpreted by the engravers and performers in this
347 The @code{\new} prefix without a name is commonly used to create
348 scores with many staves:
350 @lilypond[quote,verbatim,relative=2]
353 % leave the Voice context to be created implicitly
363 and to place several voices into one staff:
365 @lilypond[quote,verbatim,relative=2]
381 @code{\new} should always be used to specify unnamed contexts.
383 The difference between @code{\new} and @code{\context} is in the
388 @code{\new} with or without a name will always create a fresh,
389 distinct, context, even if one with the same name already exists:
391 @lilypond[quote,verbatim,relative=2]
407 @code{\context} with a name specified will create a distinct context
408 only if a context of the same type with the same name in the same
409 context hierarchy does not already exist. Otherwise it will be taken
410 as a reference to that previously created context, and its music
411 expression will be passed to that context for interpretation.
413 One application of named contexts is in separating the score layout
414 from the musical content. Either of these two forms is valid:
416 @lilypond[quote,verbatim]
430 \context Voice = "one" {
435 \context Voice = "two" {
444 @lilypond[quote,verbatim]
449 \context Voice = "one" {
452 \context Voice = "two" {
458 \context Voice = "one" {
463 \context Voice = "two" {
473 Alternatively, variables may be employed to similar effect. See
474 @rlearning{Organizing pieces with variables}.
477 @code{\context} with no name will match the first of any previously
478 created contexts of the same type in the same context heirarchy,
479 even one that has been given a name, and its music expression will be
480 passed to that context for interpretation. This form is rarely
481 useful. However, @code{\context} with no name and no music expression
482 is used to set the context in which a Scheme procedure specified with
483 @code{\applyContext} is executed:
486 \new Staff \relative @{
489 \applyContext #(lambda (ctx)
491 (display (ly:context-current-moment ctx)))
498 A context must be named if it is to be referenced later, for example
499 when lyrics are associated with music:
502 \new Voice = "tenor" @var{music}
504 \new Lyrics \lyricsto "tenor" @var{lyrics}
508 For details of associating lyrics with music see
509 @ref{Automatic syllable durations}.
511 The properties of all contexts of a particular type can be modified
512 in a @code{\layout} block (with a different syntax), see
513 @ref{Changing all contexts of the same type}. This construct also
514 provides a means of keeping layout instructions separate from the
515 musical content. If a single context is to be modified, a @code{\with}
516 block must be used, see @ref{Changing just one specific context}.
520 @rlearning{Organizing pieces with variables}.
523 @ref{Changing just one specific context},
524 @ref{Automatic syllable durations}.
527 @node Keeping contexts alive
528 @subsection Keeping contexts alive
530 @cindex contexts, keeping alive
531 @cindex contexts, lifetime
533 Contexts are usually terminated at the first musical moment in
534 which they have nothing to do. So @code{Voice} contexts die as
535 soon as they contain no events; @code{Staff} contexts die as soon
536 as all the @code{Voice} contexts within them contain no events; etc.
537 This can cause difficulties if earlier contexts which have died
538 have to be referenced, for example, when changing staves with
539 @code{\change} commands, associating lyrics with a voice with
540 @code{\lyricsto} commands, or when adding further musical events to
543 There is an exception to this general rule: just one of the
544 @code{Voice} contexts in a @code{Staff} context or in a
545 @code{<<@dots{}>>} construct will always persist to the end of the
546 enclosing @code{Staff} context or @code{<<@dots{}>>} construct, even
547 though there may be periods when it has nothing to do. The context
548 to persist in this way will be the first one encountered in the
549 first enclosed @code{@{@dots{}@}} construct, ignoring any in enclosed
550 @code{<<@dots{}>>} constructs.
552 Any context can be kept alive by ensuring it has something to do at
553 every musical moment. @code{Staff} contexts are kept alive by
554 ensuring one of their voices is kept alive. One way of doing this
555 is to add spacer rests to a voice in parallel with the real music.
556 These need to be added to every @code{Voice} context which needs to
557 be kept alive. If several voices are to be used sporadically it is
558 safest to keep them all alive rather than attempting to rely on the
559 exceptions mentioned above.
561 In the following example, both voice A and voice B are kept alive
562 in this way for the duration of the piece:
564 @lilypond[quote,verbatim]
565 musicA = \relative { d''4 d d d }
566 musicB = \relative { g'4 g g g }
569 \new Voice = "A" { s1*5 } % Keep Voice "A" alive for 5 bars
570 \new Voice = "B" { s1*5 } % Keep Voice "B" alive for 5 bars
575 \context Voice = "A" {
579 \context Voice = "B" {
583 \context Voice = "A" { \musicA }
584 \context Voice = "B" { \musicB }
585 \context Voice = "A" { \musicA }
596 @cindex lyrics, aligning with sporadic melody
598 The following example shows how a sporadic melody line with lyrics
599 might be written using this approach. In a real situation the
600 melody and accompaniment would consist of several different
603 @lilypond[quote,verbatim]
604 melody = \relative { a'4 a a a }
605 accompaniment = \relative { d'4 d d d }
606 words = \lyricmode { These words fol -- low the mel -- o -- dy }
609 \new Staff = "music" {
611 \new Voice = "melody" {
613 s1*4 % Keep Voice "melody" alive for 4 bars
616 \new Voice = "accompaniment" {
621 \context Voice = "melody" { \melody }
622 \context Voice = "accompaniment" { \accompaniment }
624 \context Voice = "accompaniment" { \accompaniment }
626 \context Voice = "melody" { \melody }
627 \context Voice = "accompaniment" { \accompaniment }
632 \new Lyrics \with { alignAboveContext = #"music" }
633 \lyricsto "melody" { \words }
638 An alternative way, which may be better in many circumstances, is
639 to keep the melody line alive by simply including spacer notes to
640 line it up correctly with the accompaniment:
642 @lilypond[quote,verbatim]
649 accompaniment = \relative {
655 words = \lyricmode { These words fol -- low the mel -- o -- dy }
659 \new Staff = "music" {
661 \new Voice = "melody" {
665 \new Voice = "accompaniment" {
671 \new Lyrics \with { alignAboveContext = #"music" }
672 \lyricsto "melody" { \words }
678 @node Modifying context plug-ins
679 @subsection Modifying context plug-ins
681 @c TODO Should this be Modifying engravers or Modifying contexts?
683 Notation contexts (like @code{Score} and @code{Staff}) not only store
684 properties, they also contain plug-ins called @q{engravers} that create
685 notation elements. For example, the @code{Voice} context contains a
686 @code{Note_heads_engraver} and the @code{Staff} context contains a
689 For a full a description of each plug-in, see
691 @rinternals{Engravers and Performers}.
694 Internals Reference @expansion{} Translation @expansion{} Engravers.
696 Every context described in
698 @rinternals{Contexts}
701 Internals Reference @expansion{} Translation @expansion{} Context.
703 lists the engravers used for that context.
706 It can be useful to shuffle around these plug-ins. This is done by
707 starting a new context with @code{\new} or @code{\context}, and
713 \new @var{context} \with @{
721 @emph{@dots{}music@dots{}}
726 where the @dots{} should be the name of an engraver. Here is a simple
727 example which removes @code{Time_signature_engraver} and
728 @code{Clef_engraver} from a @code{Staff} context,
730 @lilypond[quote,relative=1,verbatim]
736 \remove "Time_signature_engraver"
737 \remove "Clef_engraver"
744 In the second staff there are no time signature or clef symbols. This
745 is a rather crude method of making objects disappear since it will affect
746 the entire staff. This method also influences the spacing, which may or
747 may not be desirable. More sophisticated methods of blanking objects
748 are shown in @rlearning{Visibility and color of objects}.
750 The next example shows a practical application. Bar lines and time
751 signatures are normally synchronized across the score. This is done
752 by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
753 This plug-in keeps an administration of time signature, location
754 within the measure, etc. By moving these engraver from @code{Score} to
755 @code{Staff} context, we can have a score where each staff has its own
758 @cindex polymetric scores
759 @cindex time signature, multiple
761 @lilypond[quote,verbatim]
765 \consists "Timing_translator"
766 \consists "Default_bar_line_engraver"
773 \consists "Timing_translator"
774 \consists "Default_bar_line_engraver"
784 \remove "Timing_translator"
785 \remove "Default_bar_line_engraver"
793 The order in which the engravers are specified is the order in
794 which they are called to carry out their processing. Usually the
795 order in which the engravers are specified does not matter, but in
796 a few special cases the order is important, for example where one
797 engraver writes a property and another reads it, or where one
798 engraver creates a grob and another must process it.
800 The following orderings are important:
804 the @code{Bar_engraver} must normally be first,
807 the @code{New_fingering_engraver} must come before the
808 @code{Script_column_engraver},
811 the @code{Timing_translator} must come before the
812 @code{Bar_number_engraver}.
818 @file{ly/engraver-init.ly}.
821 @node Changing context default settings
822 @subsection Changing context default settings
824 @cindex default context properties, changing
825 @cindex context properties, changing defaults
827 Context and grob properties can be changed with @code{\set}
828 and @code{\override} commands, as described in
829 @ref{Modifying properties}. These commands create music events,
830 making the changes take effect at the point in time the music
833 In contrast, this section explains how to change the @emph{default}
834 values of context and grob properties at the time the context is
835 created. There are two ways of doing this. One modifies the default
836 values in all contexts of a particular type, the other modifies the
837 default values in just one particular instance of a context.
840 * Changing all contexts of the same type::
841 * Changing just one specific context::
842 * Order of precedence::
845 @node Changing all contexts of the same type
846 @unnumberedsubsubsec Changing all contexts of the same type
848 @cindex \context in \layout block
852 The default context settings which are to be used for typesetting in
853 @code{Score}, @code{Staff}, @code{Voice} and other contexts may be
854 specified in a @code{\context} block within any @code{\layout}
857 Settings for Midi output as opposed to typesetting will have to be
858 separately specified in @code{\midi} blocks (see @ref{Output
859 definitions - blueprints for contexts}).
861 The @code{\layout} block should be placed within the @code{\score}
862 block to which it is to apply, after the music.
868 [context settings for all Voice contexts]
872 [context settings for all Staff contexts]
877 The following types of settings may be specified:
881 An @code{\override} command, but with the context name omitted
883 @lilypond[quote,verbatim]
886 a'4^"Thicker stems" a a a
892 \override Stem.thickness = #4.0
899 Directly setting a context property
901 @lilypond[quote,verbatim]
904 a'4^"Smaller font" a a a
917 A predefined command such as @code{\dynamicUp} or a music
918 expression like @code{\accidentalStyle dodecaphonic}
920 @lilypond[quote,verbatim]
923 a'4^"Dynamics above" a a a
933 \accidentalStyle dodecaphonic
940 A user-defined variable containing a @code{\with} block; for details
941 of the @code{\with} block see
942 @ref{Changing just one specific context}.
944 @lilypond[quote,verbatim]
945 StaffDefaults = \with {
952 a'4^"Smaller font" a a a
967 Property-setting commands can be placed in a @code{\layout} block
968 without being enclosed in a @code{\context} block. Such settings
969 are equivalent to including the same property-setting commands at
970 the start of every context of the type specified. If no context
971 is specified @emph{every} bottom-level context is affected, see
972 @ref{Bottom-level contexts - voices}. The syntax of a
973 property-setting command in a @code{\layout} block is the same as
974 the same command written in the music stream.
976 @lilypond[quote,verbatim]
980 a'4^"Smaller font" a a a
985 \accidentalStyle dodecaphonic
987 \override Voice.Stem.thickness = #4.0
993 @node Changing just one specific context
994 @unnumberedsubsubsec Changing just one specific context
999 The context properties of just one specific context instance can be
1000 changed in a @code{\with} block. All other context instances of the
1001 same type retain the default settings built into LilyPond and modified
1002 by any @code{\layout} block within scope. The @code{\with} block
1003 must be placed immediately after the @code{\new} @var{context-type}
1007 \new Staff \with @{ [context settings for this context instance only] @}
1013 Since such a @q{context modification} is specified inside of
1014 music, it will affect @emph{all} outputs (typesetting @emph{and}
1015 Midi) as opposed to changes within an output definition.
1017 The following types of settings may be specified:
1021 An @code{\override} command, but with the context name omitted
1023 @lilypond[quote,verbatim]
1026 \new Voice \with { \override Stem.thickness = #4.0 }
1029 a'4^"Thick stems" a a a
1038 Directly setting a context property
1040 @lilypond[quote,verbatim]
1045 a'4^"Default font" a a a
1049 \new Staff \with { fontSize = #-4 }
1052 a'4^"Smaller font" a a a
1061 A predefined command such as @code{\dynamicUp}
1063 @lilypond[quote,verbatim]
1069 a'4^"Dynamics below" a a a
1074 \new Staff \with { \accidentalStyle dodecaphonic }
1076 \new Voice \with { \dynamicUp }
1079 a'4^"Dynamics above" a a a
1090 @node Order of precedence
1091 @unnumberedsubsubsec Order of precedence
1093 The value of a property which applies at a particular time is
1094 determined as follows:
1098 if an @code{\override} or @code{\set} command in the input stream is
1099 in effect that value is used,
1102 otherwise the default value taken from a @code{\with} statement
1103 on the context initiation statement is used,
1106 otherwise the default value taken from the most recent appropriate
1107 @code{\context} block in the @code{\layout} or @code{\midi} blocks
1111 otherwise the LilyPond built-in default is used.
1116 @rlearning{Modifying context properties}.
1119 @ref{Contexts explained},
1120 @ref{Bottom-level contexts - voices},
1121 @ref{The set command},
1122 @ref{The override command},
1123 @ref{The layout block,,The @code{@bs{}layout} block}.
1126 @node Defining new contexts
1127 @subsection Defining new contexts
1129 @cindex contexts, defining new
1130 @cindex engravers, including in contexts
1145 Specific contexts, like @code{Staff} and @code{Voice}, are made from
1146 simple building blocks. It is possible to create new types of
1147 contexts with different combinations of engraver plug-ins.
1149 The next example shows how to build a different type of
1150 @code{Voice} context from scratch. It will be similar to
1151 @code{Voice}, but only prints centered slash note heads. It can be used
1152 to indicate improvisation in jazz pieces,
1154 @lilypond[quote,ragged-right]
1155 \layout { \context {
1157 \type "Engraver_group"
1158 \consists "Note_heads_engraver"
1159 \consists "Rhythmic_column_engraver"
1160 \consists "Text_engraver"
1161 \consists "Pitch_squash_engraver"
1162 squashedPosition = #0
1163 \override NoteHead.style = #'slash
1168 \accepts "ImproVoice"
1172 a'4 d8 bes8 \new ImproVoice { c4^"ad lib" c
1173 c4 c^"undress" c_"while playing :)" c }
1179 These settings are defined within a @code{\context} block inside a
1180 @code{\layout} block,
1190 In the following discussion, the example input shown should go in place
1191 of the @dots{} in the previous fragment.
1193 First it is necessary to define a name for the new context:
1199 Since it is similar to the @code{Voice} context, we want commands that
1200 work in (existing) @code{Voice} contexts to continue working. This is
1201 achieved by giving the new context an alias of @code{Voice},
1207 The context will print notes and instructive texts, so we need to add
1208 the engravers which provide this functionality, plus the engraver which
1209 groups notes, stems and rests which occur at the same musical moment
1213 \consists "Note_heads_engraver"
1214 \consists "Text_engraver"
1215 \consists "Rhythmic_column_engraver"
1218 The note heads should all be placed on the center line,
1221 \consists "Pitch_squash_engraver"
1222 squashedPosition = #0
1225 The @code{Pitch_squash_engraver} modifies note heads (created
1226 by the @code{Note_heads_engraver}) and sets their vertical
1227 position to the value of @code{squashedPosition}, in this
1228 case@tie{}@code{0}, the center line.
1230 The notes look like a slash, and have no stem,
1233 \override NoteHead.style = #'slash
1237 All these plug-ins have to communicate under the control of the
1238 context. The mechanisms with which contexts communicate are
1239 established by declaring the context @code{\type}. Within a
1240 @code{\layout} block, most contexts will be of type
1241 @code{Engraver_group}. Some special contexts and contexts in
1242 @code{\midi} blocks use other context types. Copying and
1243 modifying an existing context definition will also fill in the
1244 type. Since this example creates a definition from scratch, it
1245 needs to be specified explicitly.
1248 \type "Engraver_group"
1251 Put together, we get
1256 \type "Engraver_group"
1257 \consists "Note_heads_engraver"
1258 \consists "Text_engraver"
1259 \consists "Rhythmic_column_engraver"
1260 \consists "Pitch_squash_engraver"
1261 squashedPosition = #0
1262 \override NoteHead.style = #'slash
1269 Contexts form hierarchies. We want to place the @code{ImproVoice}
1270 context within the @code{Staff} context, just like normal @code{Voice}
1271 contexts. Therefore, we modify the @code{Staff} definition with the
1272 @code{\accepts} command,
1282 The opposite of @code{\accepts} is @code{\denies},
1283 which is sometimes needed when reusing existing context definitions.
1285 Putting both into a @code{\layout} block, like
1295 \accepts "ImproVoice"
1300 Then the output at the start of this subsection can be entered as
1308 c c_"while playing :)"
1314 To complete this example, changes affecting the context hierarchy
1315 should be repeated in a @code{\midi} block so that Midi output
1316 depends on the same context relations.
1320 Internals Reference:
1321 @rinternals{Note_heads_engraver},
1322 @rinternals{Text_engraver},
1323 @rinternals{Rhythmic_column_engraver},
1324 @rinternals{Pitch_squash_engraver}.
1327 @node Context layout order
1328 @subsection Context layout order
1330 @cindex contexts, layout order
1334 Contexts are normally positioned in a system from top to bottom
1335 in the order in which they are encountered in the input file. When
1336 contexts are nested, the outer context will include inner nested
1337 contexts as specified in the input file, provided the inner contexts
1338 are included in the outer context's @qq{accepts} list. Nested
1339 contexts which are not included in the outer context's @qq{accepts}
1340 list will be repositioned below the outer context rather than nested
1343 The @qq{accepts} list of a context can be changed with the
1344 @code{\accepts} or @code{\denies} commands. @code{\accepts} adds a
1345 context to the @qq{accepts} list and @code{\denies} removes a context
1348 For example, a square-braced staff group is not usually found within a
1349 curved-braced staff with connecting staff bars, and a @code{GrandStaff}
1350 does not accept a @code{StaffGroup} inside it by default.
1352 @lilypond[verbatim,quote]
1359 \new Staff { \set Staff.instrumentName = bottom f'1 }
1364 However, by using the @code{\accepts} command, @code{StaffGroup} can be
1365 added to the @code{GrandStaff} context:
1367 @lilypond[verbatim,quote]
1374 \new Staff { \set Staff.instrumentName = bottom f'1 }
1379 \accepts "StaffGroup"
1385 @code{\denies} is mainly used when a new context is being based on
1386 another, but the required nesting differs. For example, the
1387 @code{VaticanaStaff} context is based on the @code{Staff} context, but
1388 with the @code{VaticanaVoice} context substituted for the @code{Voice}
1389 context in the @qq{accepts} list.
1391 @cindex contexts, implicit
1392 @cindex implicit contexts
1393 @funindex \defaultchild
1395 Note that a context will be silently created implicitly if a
1396 command is encountered when there is no suitable context available
1399 Within a context definition, the type of subcontext to be
1400 implicitly created is specified using @code{\defaultchild}. A
1401 number of music events require a @samp{Bottom} context: when such
1402 an event is encountered, subcontexts are created recursively until
1403 reaching a context with no @samp{defaultchild} setting.
1405 Implicit context creation can at times give rise to unexpected new
1406 staves or scores. Using @code{\new} to create contexts explicitly
1407 avoids those problems.
1409 @cindex alignAboveContext
1410 @cindex alignBelowContext
1411 @funindex alignAboveContext
1412 @funindex alignBelowContext
1414 Sometimes a context is required to exist for just a brief period, a
1415 good example being the staff context for an ossia. This is usually
1416 achieved by introducing the context definition at the appropriate
1417 place in parallel with corresponding section of the main music.
1418 By default, the temporary context will be placed below all the
1419 existing contexts. To reposition it above the context called
1420 @qq{main}, it should be defined like this:
1423 @code{\new Staff \with @{ alignAboveContext = #"main" @} }
1426 A similar situation arises when positioning a temporary lyrics
1427 context within a multi-staved layout such as a @code{ChoirStaff},
1428 for example, when adding a second verse to a repeated section.
1429 By default the temporary lyrics context will be placed beneath the
1430 lower staves. By defining the temporary lyrics context with
1431 @code{alignBelowContext} it can be positioned correctly beneath
1432 the (named) lyrics context containing the first verse.
1434 Examples showing this repositioning of temporary contexts can be
1435 found elsewhere --- see @rlearning{Nesting music expressions},
1436 @ref{Modifying single staves} and @ref{Techniques specific to lyrics}.
1440 @rlearning{Nesting music expressions}.
1443 @ref{Modifying single staves},
1444 @ref{Techniques specific to lyrics}.
1447 @rprogram{An extra staff appears}.
1450 @file{ly/engraver-init.ly}.
1453 @node Explaining the Internals Reference
1454 @section Explaining the Internals Reference
1457 * Navigating the program reference::
1458 * Layout interfaces::
1459 * Determining the grob property::
1460 * Naming conventions::
1463 @node Navigating the program reference
1464 @subsection Navigating the program reference
1466 @c TODO remove this (it's in the LM)
1467 @c Replace with more factual directions
1469 Suppose we want to move the fingering indication in the fragment
1472 @lilypond[quote,relative=2,verbatim]
1476 If you visit the documentation on fingering instructions (in
1477 @ref{Fingering instructions}), you will notice:
1482 Internals Reference: @rinternals{Fingering}.
1487 @c outdated info; probably will delete.
1489 This fragment points to two parts of the program reference: a page
1490 on @code{FingeringEvent} and one on @code{Fingering}.
1492 The page on @code{FingeringEvent} describes the properties of the music
1493 expression for the input @w{@code{-2}}. The page contains many links
1494 forward. For example, it says
1497 Accepted by: @rinternals{Fingering_engraver},
1501 That link brings us to the documentation for the Engraver, the
1505 This engraver creates the following layout objects: @rinternals{Fingering}.
1508 In other words, once the @code{FingeringEvent}s are interpreted, the
1509 @code{Fingering_engraver} plug-in will process them.
1513 @c I can't figure out what this is supposed to mean. -gp
1515 The @code{Fingering_engraver} is also listed to create
1516 @rinternals{Fingering} objects,
1518 @c old info? it doesn't make any sense to me with our current docs.
1520 second bit of information listed under @b{See also} in the Notation
1525 The programmer's reference is available as an HTML document. It is
1526 highly recommended that you read it in HTML form, either online or
1527 by downloading the HTML documentation. This section will be much more
1528 difficult to understand if you are using the
1532 Follow the link to @rinternals{Fingering}. At the top of the
1536 Fingering objects are created by: @rinternals{Fingering_engraver} and
1537 @rinternals{New_fingering_engraver}.
1540 By following related links inside the program reference, we can follow the
1541 flow of information within the program:
1545 @item @rinternals{Fingering}:
1546 @rinternals{Fingering} objects are created by:
1547 @rinternals{Fingering_engraver}
1549 @item @rinternals{Fingering_engraver}:
1550 Music types accepted: @rinternals{fingering-event}
1552 @item @rinternals{fingering-event}:
1553 Music event type @code{fingering-event} is in Music expressions named
1554 @rinternals{FingeringEvent}
1557 This path goes against the flow of information in the program: it
1558 starts from the output, and ends at the input event. You could
1559 also start at an input event, and read with the flow of
1560 information, eventually ending up at the output object(s).
1562 The program reference can also be browsed like a normal document. It
1563 contains chapters on
1565 @rinternals{Music definitions},
1568 @code{Music definitions}
1570 on @rinternals{Translation}, and the @rinternals{Backend}. Every
1571 chapter lists all the definitions used and all properties that may be
1575 @node Layout interfaces
1576 @subsection Layout interfaces
1578 @cindex interface, layout
1579 @cindex layout interface
1582 The HTML page that we found in the previous section describes the
1583 layout object called @rinternals{Fingering}. Such an object is a
1584 symbol within the score. It has properties that store numbers (like
1585 thicknesses and directions), but also pointers to related objects. A
1586 layout object is also called a @emph{Grob}, which is short for Graphical
1587 Object. For more details about Grobs, see @rinternals{grob-interface}.
1589 The page for @code{Fingering} lists the definitions for the
1590 @code{Fingering} object. For example, the page says
1593 @code{padding} (dimension, in staff space):
1599 which means that the number will be kept at a distance of at least 0.5
1603 Each layout object may have several functions as a notational or
1604 typographical element. For example, the Fingering object
1605 has the following aspects
1609 Its size is independent of the horizontal spacing, unlike slurs or beams.
1612 It is a piece of text. Granted, it is usually a very short text.
1615 That piece of text is typeset with a font, unlike slurs or beams.
1618 Horizontally, the center of the symbol should be aligned to the
1619 center of the note head.
1622 Vertically, the symbol is placed next to the note and the staff.
1625 The vertical position is also coordinated with other superscript
1626 and subscript symbols.
1629 Each of these aspects is captured in so-called @emph{interface}s,
1630 which are listed on the @rinternals{Fingering} page at the bottom
1633 This object supports the following interfaces:
1634 @rinternals{item-interface},
1635 @rinternals{self-alignment-interface},
1636 @rinternals{side-position-interface}, @rinternals{text-interface},
1637 @rinternals{text-script-interface}, @rinternals{font-interface},
1638 @rinternals{finger-interface}, and @rinternals{grob-interface}.
1641 Clicking any of the links will take you to the page of the respective
1642 object interface. Each interface has a number of properties. Some of
1643 them are not user-serviceable (@q{Internal properties}), but others
1646 We have been talking of @emph{the} @code{Fingering} object, but actually it
1647 does not amount to much. The initialization file (see
1648 @rlearning{Other sources of information})
1649 @file{scm/define-grobs.scm} shows the soul of the @q{object},
1654 (avoid-slur . around)
1655 (slur-padding . 0.2)
1656 (staff-padding . 0.5)
1657 (self-alignment-X . 0)
1658 (self-alignment-Y . 0)
1659 (script-priority . 100)
1660 (stencil . ,ly:text-interface::print)
1661 (direction . ,ly:script-interface::calc-direction)
1662 (font-encoding . fetaText)
1663 (font-size . -5) ; don't overlap when next to heads.
1664 (meta . ((class . Item)
1665 (interfaces . (finger-interface
1667 text-script-interface
1669 side-position-interface
1670 self-alignment-interface
1671 item-interface))))))
1675 As you can see, the @code{Fingering} object is nothing more than a
1676 bunch of variable settings, and the webpage in the Internals Reference
1677 is directly generated from this definition.
1680 @node Determining the grob property
1681 @subsection Determining the grob property
1683 @c TODO remove this (it's in the LM)
1684 @c Replace with more factual directions
1686 Recall that we wanted to change the position of the @b{2} in
1688 @lilypond[quote,relative=2,verbatim]
1692 Since the @b{2} is vertically positioned next to its note, we have to
1693 meddle with the interface associated with this positioning. This is
1694 done using @code{side-position-interface}. The page for this interface
1698 @code{side-position-interface}
1700 Position a victim object (this one) next to other objects (the
1701 support). The property @code{direction} signifies where to put the
1702 victim object relative to the support (left or right, up or down?)
1707 Below this description, the variable @code{padding} is described as
1712 (dimension, in staff space)
1714 Add this much extra space between objects that are next to each other.
1718 By increasing the value of @code{padding}, we can move the
1719 fingering away from the note head. The following command inserts
1720 3 staff spaces of white
1721 between the note and the fingering:
1723 \once \override Voice.Fingering.padding = #3
1726 Inserting this command before the Fingering object is created,
1727 i.e., before @code{c2}, yields the following result:
1729 @lilypond[quote,relative=2,verbatim]
1730 \once \override Voice.Fingering.padding = #3
1735 In this case, the context for this tweak is @code{Voice}. This
1736 fact can also be deduced from the program reference, for the page for
1737 the @rinternals{Fingering_engraver} plug-in says
1740 Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
1744 @node Naming conventions
1745 @subsection Naming conventions
1747 Another thing that is needed, is an overview of the various naming
1751 @item scheme functions: lowercase-with-hyphens (incl. one-word
1753 @item scheme functions: ly:plus-scheme-style
1754 @item music events, music classes and music properties:
1756 @item Grob interfaces: scheme-style
1757 @item backend properties: scheme-style (but X and Y!)
1758 @item contexts (and MusicExpressions and grobs): Capitalized or
1760 @item context properties: lowercaseFollowedByCamelCase
1762 Capitalized_followed_by_lowercase_and_with_underscores
1765 Questions to be answered:
1767 @item Which of these are conventions and which are rules?
1768 @item Which are rules of the underlying language, and which are
1772 @node Modifying properties
1773 @section Modifying properties
1775 @c TODO change the menu and subsection node names to use
1776 @c backslash once the new macro to handle the refs
1777 @c is available. Need to find and change all refs at
1778 @c the same time. -td
1781 * Overview of modifying properties::
1783 * The override command::
1784 * The tweak command::
1785 * set versus override::
1786 * Modifying alists::
1790 @node Overview of modifying properties
1791 @subsection Overview of modifying properties
1793 Each context is responsible for creating certain types of graphical
1794 objects. The settings used for printing these objects are also stored by
1795 context. By changing these settings, the appearance of objects can be
1798 There are two different kinds of properties stored in contexts:
1799 context properties and grob properties. Context properties are
1800 properties that apply to the context as a whole and control
1801 how the context itself is displayed. In contrast, grob properties
1802 apply to specific grob types that will be displayed in the context.
1804 The @code{\set} and @code{\unset} commands are used to change values
1805 for context properties. The @code{\override} and @code{\revert}
1806 commands are used to change values for grob properties.
1809 The syntax for this is
1812 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1815 Here @var{name} is the name of a graphical object, like
1816 @code{Stem} or @code{NoteHead}, and @var{property} is an internal
1817 variable of the formatting system (@q{grob property} or @q{layout
1818 property}). The latter is a symbol, so it must be quoted. The
1819 subsection @ref{Modifying properties}, explains what to fill in
1820 for @var{name}, @var{property}, and @var{value}. Here we only
1821 discuss the functionality of this command.
1826 \override Staff.Stem.thickness = #4.0
1830 makes stems thicker (the default is 1.3, with staff line thickness as a
1831 unit). Since the command specifies @code{Staff} as context, it only
1832 applies to the current staff. Other staves will keep their normal
1833 appearance. Here we see the command in action:
1835 @lilypond[quote,verbatim,relative=2]
1837 \override Staff.Stem.thickness = #4.0
1843 The @code{\override} command changes the definition of the @code{Stem}
1844 within the current @code{Staff}. After the command is interpreted
1845 all stems are thickened.
1847 Analogous to @code{\set}, the @var{context} argument may be left out,
1848 causing the default context @code{Voice} to be used. Adding
1849 @code{\once} applies the change during one timestep only.
1851 @lilypond[quote,verbatim,relative=2]
1853 \once \override Stem.thickness = #4.0
1858 The @code{\override} must be done before the object is
1859 started. Therefore, when altering @emph{Spanner} objects such as slurs
1860 or beams, the @code{\override} command must be executed at the moment
1861 when the object is created. In this example,
1863 @lilypond[quote,verbatim,relative=2]
1864 \override Slur.thickness = #3.0
1866 \override Beam.beam-thickness = #0.6
1871 the slur is fatter but the beam is not. This is because the command for
1872 @code{Beam} comes after the Beam is started, so it has no effect.
1874 Analogous to @code{\unset}, the @code{\revert} command for a context
1875 undoes an @code{\override} command; like with @code{\unset}, it only
1876 affects settings that were made in the same context. In other words, the
1877 @code{\revert} in the next example does not do anything.
1880 \override Voice.Stem.thickness = #4.0
1881 \revert Staff.Stem.thickness
1884 Some tweakable options are called @q{subproperties} and reside inside
1885 properties. To tweak those, use commands of the form
1887 @c leave this as a long long
1889 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
1896 \override Stem.details.beamed-lengths = #'(4 4 3)
1902 Internals Reference:
1903 @rinternals{Backend},
1904 @rinternals{All layout objects},
1905 @rinternals{OverrideProperty},
1906 @rinternals{RevertProperty},
1907 @rinternals{PropertySet}.
1910 The back-end is not very strict in type-checking object properties.
1911 Cyclic references in Scheme values for properties can cause hangs
1912 or crashes, or both.
1915 @node The set command
1916 @subsection The @code{@bs{}set} command
1920 @cindex changing properties
1922 Each context has a set of @emph{properties}, variables contained
1923 in that context. Context properties are changed with the @code{\set}
1924 command, which has the following syntax:
1927 \set @var{context}.@var{property} = #@var{value}
1930 @var{value} is a Scheme object, which is why it must be preceded by
1931 the @code{#}@tie{}character.
1933 Contexts properties are usually named in
1934 @code{studlyCaps}. They mostly control the translation from
1935 music to notation, e.g. @code{localAlterations} (for determining
1936 whether to print accidentals), or @code{measurePosition} (for
1937 determining when to print a bar line). Context properties can
1938 change value over time while interpreting a piece of music;
1939 @code{measurePosition} is an obvious example of
1940 this. Context properties are modified with @code{\set}.
1942 For example, multimeasure rests will be combined into a single bar
1943 if the context property @code{skipBars} is set to @code{#t}:
1945 @lilypond[quote,verbatim,relative=2]
1947 \set Score.skipBars = ##t
1951 If the @var{context} argument is left out, then the property will be
1952 set in the current bottom context (typically @code{ChordNames},
1953 @code{Voice}, @code{TabVoice}, or @code{Lyrics}).
1955 @lilypond[quote,verbatim,relative=2]
1956 \set Score.autoBeaming = ##f
1960 \set autoBeaming = ##t
1968 The change is applied @q{on-the-fly}, during the music, so that the
1969 setting only affects the second group of eighth notes.
1971 Note that the bottom-most context does not always contain the property
1972 that you wish to change -- for example, attempting to set the
1973 @code{skipBars} property of the default bottom context, in this case
1974 @code{Voice}, will have no effect, because skipBars is a property of
1975 the @code{Score} context.
1977 @lilypond[quote,verbatim,relative=2]
1983 Contexts are hierarchical, so if an enclosing context was specified, for
1984 example @code{Staff}, then the change would also apply to all
1985 @code{Voice}s in the current staff.
1989 The @code{\unset} command:
1992 \unset @var{context}.@var{property}
1996 is used to remove the definition of @var{property} from
1997 @var{context}. This command removes
1998 the definition only if it is set in @var{context}.
1999 Properties that have been set in enclosing contexts will
2000 not be altered by an unset in an enclosed context:
2002 @lilypond[quote,verbatim,relative=2]
2003 \set Score.autoBeaming = ##t
2008 \unset Score.autoBeaming
2016 Like @code{\set}, the @var{context} argument does not have to be
2017 specified for a bottom context, so the two statements
2020 \set Voice.autoBeaming = ##t
2021 \set autoBeaming = ##t
2025 are equivalent if the current bottom context is @code{Voice}.
2029 Preceding a @code{\set} command by @code{\once} makes the
2030 setting apply to only a single time-step:
2032 @lilypond[quote,verbatim,relative=2]
2034 \once \set fontSize = #4.7
2039 A full description of all available context properties is in the
2040 internals reference, see
2042 @rinternals{Tunable context properties}.
2045 Translation @expansion{} Tunable context properties.
2049 Internals Reference:
2050 @rinternals{Tunable context properties}.
2053 @node The override command
2054 @subsection The @code{\override} command
2056 @cindex grob properties
2057 @cindex properties, grob
2060 There is a special type of context property: the grob
2061 description. Grob descriptions are named in @code{StudlyCaps}
2062 (starting with capital letters). They contain the
2063 @q{default settings} for a particular kind of grob as an
2064 association list. See @file{scm/define-grobs.scm}
2065 to see the settings for each grob description. Grob descriptions
2066 are modified with @code{\override}.
2068 The syntax for the @code{\override} command is
2071 \override [@var{context}.]@var{GrobName}.@var{property} = #@var{value}
2074 For example, we can increase the thickness of a note stem by
2075 overriding the @code{thickness} property of the @code{Stem}
2078 @lilypond[quote,verbatim,relative=2]
2080 \override Voice.Stem.thickness = #3.0
2084 If no context is specified in an @code{\override}, the bottom
2087 @lilypond[quote,verbatim,relative=2]
2088 { \override Staff.Stem.thickness = #3.0
2092 \override Stem.thickness = #0.5
2101 Some tweakable options are called @q{subproperties} and reside inside
2102 properties. To tweak those, use commands in the form
2105 \override Stem.details.beamed-lengths = #'(4 4 3)
2108 or to modify the ends of spanners, use a form like these
2111 \override TextSpanner.bound-details.left.text = #"left text"
2112 \override TextSpanner.bound-details.right.text = #"right text"
2116 @cindex reverting overrides
2117 @cindex overrides, reverting
2119 The effects of @code{\override} can be undone by @code{\revert}.
2121 The syntax for the @code{\revert} command is
2124 \revert [@var{context}.]@var{GrobName}.@var{property}
2129 @lilypond[quote,verbatim,relative=2]
2131 \override Voice.Stem.thickness = #3.0
2133 \revert Voice.Stem.thickness
2137 The effects of @code{\override} and @code{\revert} apply to all
2138 grobs in the affected context from the current time forward:
2140 @lilypond[quote,verbatim,relative=2]
2145 \override Staff.Stem.thickness = #3.0
2149 \revert Staff.Stem.thickness
2157 @cindex overriding for only one moment
2159 @code{\once} can be used with @code{\override}
2160 to affect only the current time step:
2162 @lilypond[quote,verbatim,relative=2]
2166 \override Stem.thickness = #3.0
2170 \once \override Stem.thickness = #3.0
2179 Commands which change output generally look like
2182 \override Voice.Stem.thickness = #3.0
2186 To construct this tweak we must determine these bits of information:
2189 @item the context: here @code{Voice}.
2190 @item the layout object: here @code{Stem}.
2191 @item the layout property: here @code{thickness}.
2192 @item a sensible value: here @code{3.0}.
2195 @cindex internal documentation
2196 @cindex finding graphical objects
2197 @cindex graphical object descriptions
2200 @cindex internal documentation
2202 For many properties, regardless of the data type of the property, setting the
2203 property to false (@code{#f}) will result in turning it off, causing
2204 LilyPond to ignore that property entirely. This is particularly useful for
2205 turning off grob properties which may otherwise be causing problems.
2207 We demonstrate how to glean this information from the notation manual
2208 and the program reference.
2212 Internals Reference:
2213 @rinternals{Backend}
2216 @node The tweak command
2217 @subsection The @code{\tweak} command
2222 Changing grob properties
2223 with @code{\override} causes the changes to apply to all of the
2224 given grobs in the context at the moment the change applies.
2225 Sometimes, however, it is desirable to have changes apply to just
2226 one grob, rather than to all grobs in the affected context. This is
2227 accomplished with the @code{\tweak} command, which has the following
2231 \tweak [@var{layout-object}.]@var{grob-property} @var{value}
2234 Specifying @var{layout-object} is optional.
2235 The @code{\tweak} command applies to the music object that immediately
2236 follows @var{value} in the music stream.
2239 In some cases, it is possible to take a short-cut for tuning
2240 graphical objects. For objects that are created directly from
2241 an item in the input file, you can use the @code{\tweak} command.
2244 @lilypond[relative=2,verbatim,quote]
2249 \tweak duration-log #1
2258 The main use of the @code{\tweak} command is to modify just
2259 one of a number of notation elements which start at the same musical
2260 moment, like the notes of a chord, or tuplet brackets which start
2263 The @code{\tweak} command sets a property in the following object
2264 directly, without requiring the grob name or context to be
2265 specified. For this to work, it is necessary for the @code{\tweak}
2266 command to remain immediately adjacent to the object to which it is
2267 to apply after the input file has been converted to a music stream.
2268 This is often not the case, as many additional elements are inserted
2269 into the music stream implicitly. For example, when a note which is
2270 not part of a chord is processed, LilyPond implicitly inserts a
2271 @code{ChordEvent} event before the note, so separating the tweak
2272 from the note. However, if chord symbols are placed round the
2273 tweak and the note, the @code{\tweak} command comes after the
2274 @code{ChordEvent} in the music stream, so remaining adjacent to the
2275 note, and able to modify it.
2279 @lilypond[relative=2,verbatim,quote]
2280 <\tweak color #red c>4
2286 @lilypond[relative=2,verbatim,quote]
2287 \tweak color #red c4
2292 For an introduction to the syntax and uses of the tweak command
2293 see @rlearning{Tweaking methods}.
2295 When several similar items are placed at the same musical moment,
2296 the @code{\override} command cannot be used to modify just one of
2297 them -- this is where the @code{\tweak} command must be used.
2298 Items which may appear more than once at the same musical moment
2299 include the following:
2301 @c TODO expand to include any further uses of \tweak
2303 @item note heads of notes inside a chord
2304 @item articulation signs on a single note
2305 @item ties between notes in a chord
2306 @item tuplet brackets starting at the same time
2309 @c TODO add examples of these
2311 @cindex chord, modifying one note in
2313 In this example, the color of one note head and the type of another
2314 note head are modified within a single chord:
2316 @lilypond[relative=2,verbatim,quote]
2321 \tweak duration-log #1
2326 @code{\tweak} can be used to modify slurs:
2328 @lilypond[verbatim,quote,relative=1]
2329 c-\tweak thickness #5 ( d e f)
2333 For the @code{\tweak} command to work, it must
2334 remain immediately adjacent to the object to which it is
2335 to apply after the input file has been converted to a music stream.
2336 Tweaking a whole chord does not do anything since its music event
2337 only acts as a container, and all layout objects are created from events
2338 inside of the @code{EventChord}:
2340 @lilypond[relative=2,verbatim,quote]
2341 \tweak color #red c4
2342 \tweak color #red <c e>4
2343 <\tweak color #red c e>4
2346 The simple @code{\tweak} command cannot be used to modify any object
2347 that is not directly created from the input. In particular
2348 it will not affect stems, automatic
2349 beams or accidentals, since these are generated later by
2350 @code{NoteHead} layout objects rather than by music elements in the
2353 Such indirectly created layout objects can be tweaked using the form
2354 of the @code{\tweak} command in which the grob name is specified
2357 @lilypond[relative=2,verbatim,quote]
2358 \tweak Stem.color #red
2359 \tweak Beam.color #green c8 e
2360 <c e \tweak Accidental.font-size #-3 ges>4
2363 @code{\tweak} cannot be used to modify clefs or time
2364 signatures, since these become separated from any preceding
2365 @code{\tweak} command in the input stream by the automatic
2366 insertion of extra elements required to specify the context.
2368 Several @code{\tweak} commands may be placed before a
2369 notational element -- all affect it:
2371 @lilypond[verbatim,quote,relative=1]
2373 -\tweak style #'dashed-line
2374 -\tweak dash-fraction #0.2
2375 -\tweak thickness #3
2381 The music stream which is generated from a section of an input file,
2382 including any automatically inserted elements, may be examined,
2383 see @rextend{Displaying music expressions}. This may be helpful in
2384 determining what may be modified by a @code{\tweak} command, or
2385 in determining how to adjust the input to make a @code{\tweak}
2390 @rlearning{Tweaking methods}.
2393 @rextend{Displaying music expressions}.
2397 @cindex tweaking control points
2398 @cindex control points, tweaking
2400 The @code{\tweak} command cannot be used to modify the control
2401 points of just one of several ties in a chord, other than the first
2402 one encountered in the input file.
2404 @node set versus override
2405 @subsection @code{\set} vs. @code{\override}
2407 @c TODO Should't a bunch of that be explained earlier?
2411 Both @code{\set} and @code{\override} manipulate properties
2412 associated with contexts. In either case, properties heed the
2413 hierarchy of contexts: properties not set in a context itself show
2414 the values of the respective parent context.
2416 Values and lifetime of context properties are dynamic and only
2417 available when music is being interpreted, @q{iterated}. At the
2418 time of context creation, properties are initialized from the
2419 corresponding context definition and possible context
2420 modifications. Afterwards, changes are achieved with
2421 property-setting commands in the music itself.
2423 Now grob definitions are a special category of context properties.
2424 Since their structure, bookkeeping and use is different from
2425 ordinary context properties, they are accessed with a different
2426 set of commands, and treated separately in the documentation.
2428 As opposed to plain context properties, grob definitions are
2429 subdivided into grob properties. A @qq{grob} (graphical object)
2430 is usually created by an engraver at the time of interpreting a
2431 music expression and receives its initial properties from the
2432 current grob definition of the engraver's context. The engraver
2433 (or other @q{backend} parts of LilyPond) may subsequently add or
2434 change properties to the grob, but that does not affect the
2435 context's grob definition.
2437 What we call @q{grob properties} in the context of user-level
2438 tweaking are actually the properties of a context's grob
2439 definition. In contrast to ordinary context properties, grob
2440 definitions have the bookkeeping required to keep track of its
2441 parts, the individual grob properties (and even subproperties of
2442 them) separately so that it is possible to define those parts in
2443 different contexts and have the overall grob definition at the
2444 time of grob creation be assembled from pieces provided in
2445 different contexts among the current context and its parents.
2447 Grob definitions are manipulated using @code{\override} and
2448 @code{\revert} and have a name starting with a capital letter
2449 (like @samp{NoteHead}) whereas ordinary context properties are
2450 manipulated using @code{\set} and @code{\unset} and are named
2451 starting with a lowercase letter.
2453 @cindex tweak, relation to @code{\override}
2455 @funindex \overrideProperty
2456 The special commands @code{\tweak} and @code{\overrideProperty}
2457 change grob properties bypassing context properties completely.
2458 Instead they catch grobs as they are being created and then
2459 directly set properties on them when they originate from a tweaked
2460 music event or are of a particular kind, respectively.
2462 @node Modifying alists
2463 @subsection Modifying alists
2465 Some user-configurable properties are internally represented as
2466 @emph{alists} (association lists), which store pairs of
2467 @emph{keys} and @emph{values}. The structure of an alist is:
2470 '((@var{key1} . @var{value1})
2471 (@var{key2} . @var{value2})
2472 (@var{key3} . @var{value3})
2476 If an alist is a grob property or @code{\paper} variable, its keys
2477 can be modified individually without affecting other keys.
2479 For example, to reduce the space between adjacent staves in a
2480 staff-group, use the @code{staff-staff-spacing} property of the
2481 @code{StaffGrouper} grob. The property is an alist with four
2482 keys: @code{basic-distance}, @code{minimum-distance},
2483 @code{padding}, and @code{stretchability}. The standard settings
2484 for this property are listed in the @qq{Backend} section of the
2485 Internals Reference (see @rinternals{StaffGrouper}):
2488 '((basic-distance . 9)
2489 (minimum-distance . 7)
2491 (stretchability . 5))
2494 One way to bring the staves closer together is by reducing the
2495 value of the @code{basic-distance} key (@code{9}) to match the
2496 value of @code{minimum-distance} (@code{7}). To modify a single
2497 key individually, use a @emph{nested declaration}:
2499 @lilypond[quote,verbatim]
2500 % default space between staves
2502 \new Staff { \clef treble c''1 }
2503 \new Staff { \clef bass c1 }
2506 % reduced space between staves
2507 \new PianoStaff \with {
2508 % this is the nested declaration
2509 \override StaffGrouper.staff-staff-spacing.basic-distance = #7
2511 \new Staff { \clef treble c''1 }
2512 \new Staff { \clef bass c1 }
2516 Using a nested declaration will update the specified key (such as
2517 @code{basic-distance} in the above example) without altering any
2518 other keys already set for the same property.
2520 Now suppose we want the staves to be as close as possible without
2521 overlapping. The simplest way to do this is to set all four alist
2522 keys to zero. However, it is not necessary to enter four nested
2523 declarations, one for each key. Instead, the property can be
2524 completely re-defined with one declaration, as an alist:
2526 @lilypond[quote,verbatim]
2527 \new PianoStaff \with {
2528 \override StaffGrouper.staff-staff-spacing =
2529 #'((basic-distance . 0)
2530 (minimum-distance . 0)
2532 (stretchability . 0))
2534 \new Staff { \clef treble c''1 }
2535 \new Staff { \clef bass c1 }
2539 Note that any keys not explicitly listed in the alist definition
2540 will be reset to their @emph{default-when-unset} values. In the
2541 case of @code{staff-staff-spacing}, any unset key-values would be
2542 reset to zero (except @code{stretchability}, which takes the value
2543 of @code{basic-distance} when unset). Thus the following two
2544 declarations are equivalent:
2547 \override StaffGrouper.staff-staff-spacing =
2548 #'((basic-distance . 7))
2550 \override StaffGrouper.staff-staff-spacing =
2551 #'((basic-distance . 7)
2552 (minimum-distance . 0)
2554 (stretchability . 7))
2557 One (possibly unintended) consequence of this is the removal of
2558 any standard settings that are set in an initialization file and
2559 loaded each time an input file is compiled. In the above example,
2560 the standard settings for @code{padding} and
2561 @code{minimum-distance} (defined in @file{scm/define-grobs.scm})
2562 are reset to their default-when-unset values (zero for both keys).
2563 Defining a property or variable as an alist (of any size) will
2564 always reset all unset key-values to their default-when-unset
2565 values. Unless this is the intended result, it is safer to update
2566 key-values individually with a nested declaration.
2568 @warning{Nested declarations will not work for context property
2569 alists (such as @code{beamExceptions}, @code{keyAlterations},
2570 @code{timeSignatureSettings}, etc.). These properties can only be
2571 modified by completely re-defining them as alists.}
2574 @node Useful concepts and properties
2575 @section Useful concepts and properties
2580 * Direction and placement::
2581 * Distances and measurements::
2583 * Staff symbol properties::
2585 * Visibility of objects::
2587 * Rotating objects::
2591 @subsection Input modes
2593 The way in which the notation contained within an input file is
2594 interpreted is determined by the current input mode.
2596 @subsubsubheading Chord mode
2598 This is activated with the @code{\chordmode} command, and causes
2599 input to be interpreted with the syntax of chord notation, see
2600 @ref{Chord notation}. Chords are rendered as notes on a staff.
2602 Chord mode is also activated with the @code{\chords} command.
2603 This also creates a new @code{ChordNames} context and
2604 causes the following input to be interpreted with the syntax of
2605 chord notation and rendered as chord names in the @code{ChordNames}
2606 context, see @ref{Printing chord names}.
2608 @subsubsubheading Drum mode
2610 This is activated with the @code{\drummode} command, and causes
2611 input to be interpreted with the syntax of drum notation, see
2612 @ref{Basic percussion notation}.
2614 Drum mode is also activated with the @code{\drums} command.
2615 This also creates a new @code{DrumStaff} context and causes the
2616 following input to be interpreted with the syntax of drum notation
2617 and rendered as drum symbols on a drum staff, see
2618 @ref{Basic percussion notation}.
2620 @subsubsubheading Figure mode
2622 This is activated with the @code{\figuremode} command, and causes
2623 input to be interpreted with the syntax of figured bass, see
2624 @ref{Entering figured bass}.
2626 Figure mode is also activated with the @code{\figures} command.
2627 This also creates a new @code{FiguredBass} context and causes the
2628 following input to be interpreted with the figured bass syntax
2629 and rendered as figured bass symbols in the @code{FiguredBass}
2630 context, see @ref{Introduction to figured bass}.
2632 @subsubsubheading Fret and tab modes
2634 There are no special input modes for entering fret and tab symbols.
2636 To create tab diagrams, enter notes or chords in note mode and
2637 render them in a @code{TabStaff} context, see
2638 @ref{Default tablatures}.
2640 To create fret diagrams above a staff, you have two choices.
2641 You can either use the @code{FretBoards} context (see
2642 @ref{Automatic fret diagrams} or you can enter them as a markup
2643 above the notes using the @code{\fret-diagram} command (see
2644 @ref{Fret diagram markups}).
2646 @subsubsubheading Lyrics mode
2648 This is activated with the @code{\lyricmode} command, and causes
2649 input to be interpreted as lyric syllables with optional durations
2650 and associated lyric modifiers, see @ref{Vocal music}.
2652 Lyric mode is also activated with the @code{\addlyrics} command.
2653 This also creates a new @code{Lyrics} context and an implicit
2654 @code{\lyricsto} command which associates the following lyrics
2655 with the preceding music.
2657 @subsubsubheading Markup mode
2659 This is activated with the @code{\markup} command, and causes
2660 input to be interpreted with the syntax of markup, see
2661 @ref{Text markup commands}.
2663 @subsubsubheading Note mode
2665 This is the default mode or it may be activated with the
2666 @code{\notemode} command. Input is interpreted as pitches,
2667 durations, markup, etc and typeset as musical notation on a staff.
2669 It is not normally necessary to specify note mode explicitly, but
2670 it may be useful to do so in certain situations, for example if you
2671 are in lyric mode, chord mode or any other mode and want to insert
2672 something that only can be done with note mode syntax.
2675 @node Direction and placement
2676 @subsection Direction and placement
2678 In typesetting music the direction and placement of many items is
2679 a matter of choice. For example, the stems of notes can
2680 be directed up or down; lyrics, dynamics, and other expressive
2681 marks may be placed above or below the staff; text may be aligned
2682 left, right or center; etc. Most of these choices may be left to
2683 be determined automatically by LilyPond, but in some cases it may
2684 be desirable to force a particular direction or placement.
2687 * Articulation direction indicators::
2688 * The direction property::
2691 @node Articulation direction indicators
2692 @unnumberedsubsubsec Articulation direction indicators
2694 By default some directions are always up or always down (e.g.
2695 dynamics or fermata), while other things can alternate between
2696 up or down based on the stem direction (like slurs or accents).
2698 @c TODO Add table showing these
2700 The default action may be overridden by prefixing the articulation
2701 by a @emph{direction indicator}. Three direction indicators are
2702 available: @code{^} (meaning @qq{up}), @code{_} (meaning @qq{down})
2703 and @code{-} (meaning @qq{use default direction}). The direction
2704 indicator can usually be omitted, in which case @code{-} is assumed,
2705 but a direction indicator is @strong{always} required before
2708 @item @code{\tweak} commands
2709 @item @code{\markup} commands
2710 @item @code{\tag} commands
2711 @item string markups, e.g. -"string"
2712 @item fingering instructions, e.g. @w{@code{-1}}
2713 @item articulation shortcuts, e.g. @w{@code{-.}}, @w{@code{->}}, @w{@code{--}}
2716 Direction indicators affect only the next note:
2718 @lilypond[verbatim,quote,relative=2]
2725 @node The direction property
2726 @unnumberedsubsubsec The direction property
2728 The position or direction of many layout objects is controlled by the
2729 @code{direction} property.
2731 The value of the @code{direction} property may be set to @code{1},
2732 meaning @qq{up} or @qq{above}, or to @w{@code{-1}}, meaning @qq{down} or
2733 @qq{below}. The symbols @code{UP} and @code{DOWN} may be used instead
2734 of @code{1} and @w{@code{-1}} respectively. The default direction may
2735 be specified by setting @code{direction} to @code{0} or @code{CENTER}.
2736 Alternatively, in many cases predefined commands exist to specify the
2737 direction. These are of the form
2740 @code{\xxxUp}, @code{\xxxDown} or @code{\xxxNeutral}
2744 where @code{\xxxNeutral} means @qq{use the default} direction.
2745 See @rlearning{Within-staff objects}.
2747 In a few cases, arpeggio for example, the value of the @code{direction}
2748 property can specify whether the object is to be placed to the right or
2749 left of the parent. In this case @w{@code{-1}} or @code{LEFT} means
2750 @qq{to the left} and @code{1} or @code{RIGHT} means @qq{to the right}.
2751 @code{0} or @code{CENTER} means @qq{use the default} direction.
2754 These all have side-axis set to #X
2755 AmbitusAccidental - direction has no effect
2757 StanzaNumber - not tried
2758 TrillPitchAccidental - not tried
2759 TrillPitchGroup - not tried
2762 These indications affect all notes until they are canceled.
2764 @lilypond[verbatim,quote,relative=2]
2773 In polyphonic music, it is generally better to specify an explicit
2774 @code{voice} than change an object's direction. For more information.
2775 See @ref{Multiple voices}.
2779 @rlearning{Within-staff objects}.
2782 @ref{Multiple voices}.
2785 @node Distances and measurements
2786 @subsection Distances and measurements
2788 @cindex distances, absolute
2789 @cindex distances, scaled
2796 Distances in LilyPond are of two types: absolute and scaled.
2798 Absolute distances are used for specifying margins, indents, and
2799 other page layout details, and are by default specified in
2800 millimeters. Distances may be specified in other units by
2801 following the quantity by @code{\mm}, @code{\cm},
2802 @code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27 of
2803 an inch). Page layout distances can also be specified in scalable
2804 units (see the following paragraph) by appending
2805 @code{\staff-space} to the quantity. Page layout is described in
2806 detail in @ref{Page layout}.
2808 Scaled distances are always specified in units of the staff-space
2809 or, rarely, the half staff-space. The staff-space is the distance
2810 between two adjacent staff lines. The default value can be changed
2811 globally by setting the global staff size, or it can be overridden
2812 locally by changing the @code{staff-space} property of
2813 @code{StaffSymbol}. Scaled distances automatically scale with any
2814 change to the either the global staff size or the
2815 @code{staff-space} property of @code{StaffSymbol}, but fonts scale
2816 automatically only with changes to the global staff size.
2817 The global staff size thus enables the overall size of a rendered
2818 score to be easily varied. For the methods of setting the global
2819 staff size see @ref{Setting the staff size}.
2823 If just a section of a score needs to be rendered to a different
2824 scale, for example an ossia section or a footnote, the global staff
2825 size cannot simply be changed as this would affect the entire score.
2826 In such cases the change in size is made by overriding both the
2827 @code{staff-space} property of @code{StaffSymbol} and the size of
2828 the fonts. A Scheme function, @code{magstep}, is available to
2829 convert from a font size change to the equivalent change in
2830 @code{staff-space}. For an explanation and an example of its use,
2831 see @rlearning{Length and thickness of objects}.
2835 @rlearning{Length and thickness of objects}.
2839 @ref{Setting the staff size}.
2843 @subsection Dimensions
2846 @cindex bounding box
2848 The dimensions of a graphical object specify the positions of the left
2849 and right edges and the bottom and top edges of the objects' bounding
2850 box as distances from the objects' reference point in units of
2851 staff-spaces. These positions are usually coded as two Scheme pairs.
2852 For example, the text markup command @code{\with-dimensions} takes
2853 three arguments, the first two of which are a Scheme pair giving the
2854 left and right edge positions and a Scheme pair giving the bottom and
2858 \with-dimensions #'(-5 . 10) #'(-3 . 15) @var{arg}
2861 This specifies a bounding box for @var{arg} with its left edge at -5,
2862 its right edge at 10, its bottom edge at -3 and its top edge at 15,
2863 all measured from the objects' reference point in units of
2868 @ref{Distances and measurements}.
2871 @node Staff symbol properties
2872 @subsection Staff symbol properties
2874 @cindex adjusting staff symbol
2875 @cindex drawing staff symbol
2876 @cindex staff symbol, setting of
2878 @c TODO Extend or remove this section. See also NR 1.6.2 Staff symbol
2879 @c Need to think of uses for these properties. Eg 'line-positions
2880 @c is used in a snippet to thicken centre line.
2881 @c If retained, add @ref to here in 1.6.2 -td
2883 The vertical position of staff lines and the number of staff lines
2884 can be defined at the same time. As the following example shows,
2885 note positions are not influenced by the staff line positions.
2887 @warning{The @code{'line-positions} property overrides the
2888 @code{'line-count} property. The number of staff lines is
2889 implicitly defined by the number of elements in the list of values
2890 for @code{'line-positions}.}
2892 @lilypond[verbatim,quote,relative=1]
2894 \override StaffSymbol.line-positions = #'(7 3 0 -4 -6 -7)
2899 The width of a staff can be modified. The units are staff
2900 spaces. The spacing of objects inside the staff is not affected by
2903 @lilypond[verbatim,quote,relative=1]
2905 \override StaffSymbol.width = #23
2912 @subsection Spanners
2914 Many objects of musical notation extend over several notes or even
2915 several bars. Examples are slurs, beams, tuplet brackets, volta
2916 repeat brackets, crescendi, trills, and glissandi. Such objects
2917 are collectively called @qq{spanners}, and have special properties to control
2918 their appearance and behaviour. Some of these properties are common
2919 to all spanners; others are restricted to a sub-set of the spanners.
2921 All spanners support the @code{spanner-interface}. A few, essentially
2922 those that draw a straight line between the two objects, support in
2923 addition the @code{line-spanner-interface}.
2926 * Using the spanner-interface::
2927 * Using the line-spanner-interface::
2930 @node Using the spanner-interface
2931 @unnumberedsubsubsec Using the @code{spanner-interface}
2933 This interface provides two properties that apply to several spanners.
2935 @subsubsubheading The @code{minimum-length} property
2937 The minimum length of the spanner is specified by the
2938 @code{minimum-length} property. Increasing this usually has the
2939 necessary effect of increasing the spacing of the notes between the
2940 two end points. However, this override has no effect on
2941 many spanners, as their length is determined by other considerations.
2942 A few examples where it is effective are shown below.
2952 Works as long as callback is made:
2956 Works not at all for:
2965 @lilypond[verbatim,quote,relative=2]
2968 % increase the length of the tie
2969 -\tweak minimum-length #5
2973 @lilypond[verbatim,quote,relative=2]
2977 % increase the length of the rest bar
2978 \once \override MultiMeasureRest.minimum-length = #20
2984 @lilypond[verbatim,quote,relative=2]
2986 % increase the length of the hairpin
2987 \override Hairpin.minimum-length = #20
2991 This override can also be used to increase the length of slurs and
2994 @lilypond[verbatim,quote,relative=2]
2997 -\tweak minimum-length #5
3002 -\tweak minimum-length #5
3006 For some layout objects, the @code{minimum-length} property becomes
3007 effective only if the @code{set-spacing-rods} procedure is called
3008 explicitly. To do this, the @code{springs-and-rods} property should
3009 be set to @code{ly:spanner::set-spacing-rods}. For example,
3010 the minimum length of a glissando has no effect unless the
3011 @code{springs-and-rods} property is set:
3013 @lilypond[verbatim,quote,relative=1]
3017 % not effective alone
3018 \once \override Glissando.minimum-length = #20
3021 % effective only when both overrides are present
3022 \once \override Glissando.minimum-length = #20
3023 \once \override Glissando.springs-and-rods = #ly:spanner::set-spacing-rods
3027 The same is true of the @code{Beam} object:
3029 @lilypond[verbatim,quote,relative=1]
3030 % not effective alone
3031 \once \override Beam.minimum-length = #20
3034 % effective only when both overrides are present
3035 \once \override Beam.minimum-length = #20
3036 \once \override Beam.springs-and-rods = #ly:spanner::set-spacing-rods
3040 @subsubsubheading The @code{to-barline} property
3042 The second useful property of the @code{spanner-interface} is
3043 @code{to-barline}. By default this is true, causing hairpins and
3044 other spanners which are terminated on the first note of a measure to
3045 end instead on the immediately preceding bar line. If set to false,
3046 the spanner will extend beyond the bar line and end on the note
3049 @lilypond[verbatim,quote,relative=2]
3050 a \< a a a a \! a a a \break
3051 \override Hairpin.to-barline = ##f
3052 a \< a a a a \! a a a
3055 This property is not effective for all spanners. For example,
3056 setting it to @code{#t} has no effect on slurs or phrasing slurs
3057 or on other spanners for which terminating on the bar line would
3060 @node Using the line-spanner-interface
3061 @unnumberedsubsubsec Using the @code{line-spanner-interface}
3063 Objects which support the @code{line-spanner-interface} include
3066 @item @code{DynamicTextSpanner}
3067 @item @code{Glissando}
3068 @item @code{TextSpanner}
3069 @item @code{TrillSpanner}
3070 @item @code{VoiceFollower}
3073 The routine responsible for drawing the stencils for these spanners is
3074 @code{ly:line-spanner::print}. This routine determines the
3075 exact location of the two end points and draws a line
3076 between them, in the style requested. The locations of the two
3077 end points of the spanner are computed on-the-fly, but it is
3078 possible to override their Y-coordinates. The
3079 properties which need to be specified are nested
3080 two levels down within the property hierarchy, but the syntax of
3081 the @code{\override} command is quite simple:
3083 @lilypond[relative=2,quote,verbatim]
3085 \once \override Glissando.bound-details.left.Y = #3
3086 \once \override Glissando.bound-details.right.Y = #-2
3090 The units for the @code{Y} property are @code{staff-space}s,
3091 with the center line of the staff being the zero point.
3092 For the glissando, this is the value for @code{Y} at the
3093 X-coordinate corresponding to the center point of each note head,
3094 if the line is imagined to be extended to there.
3096 If @code{Y} is not set, the value is computed from the vertical
3097 position of the corresponding attachment point of the spanner.
3099 In case of a line break, the values for the end points are
3100 specified by the @code{left-broken} and @code{right-broken}
3101 sub-lists of @code{bound-details}. For example:
3103 @lilypond[relative=2,ragged-right,verbatim,quote]
3104 \override Glissando.breakable = ##t
3105 \override Glissando.bound-details.right-broken.Y = #-3
3106 c1 \glissando \break
3111 A number of further properties of the @code{left} and
3112 @code{right} sub-lists of the @code{bound-details} property
3113 may be modified in the same way as @code{Y}:
3117 This sets the Y-coordinate of the end point, in @code{staff-space}s
3118 offset from the staff center line. By default, it is the center of
3119 the bound object, so a glissando points to the vertical center of
3122 For horizontal spanners, such as text spanners and trill spanners,
3123 it is hardcoded to 0.
3126 This determines where the line starts and ends in the X-direction,
3127 relative to the bound object. So, a value of @w{@code{-1}} (or
3128 @code{LEFT}) makes the line start/end at the left side of the note
3129 head it is attached to.
3132 This is the absolute X-coordinate of the end point. It is usually
3133 computed on the fly, and overriding it has little useful effect.
3136 Line spanners may have symbols at the beginning or end, which is
3137 contained in this sub-property. This is for internal use; it is
3138 recommended that @code{text} be used instead.
3141 This is a markup that is evaluated to yield the stencil. It is used
3142 to put @i{cresc.}, @i{tr} and other text on horizontal spanners.
3144 @lilypond[quote,ragged-right,relative=2,verbatim]
3145 \override TextSpanner.bound-details.left.text
3146 = \markup { \small \bold Slower }
3147 c2\startTextSpan b c a\stopTextSpan
3150 @item stencil-align-dir-y
3151 @item stencil-offset
3152 Without setting one of these, the stencil is simply put at the
3153 end-point, centered on the line, as defined by the @code{X} and
3154 @code{Y} sub-properties. Setting either @code{stencil-align-dir-y}
3155 or @code{stencil-offset} will move the symbol at the edge vertically
3156 relative to the end point of the line:
3158 @lilypond[relative=1,quote,verbatim]
3159 \override TextSpanner.bound-details.left.stencil-align-dir-y = #-2
3160 \override TextSpanner.bound-details.right.stencil-align-dir-y = #UP
3162 \override TextSpanner.bound-details.left.text = #"ggg"
3163 \override TextSpanner.bound-details.right.text = #"hhh"
3164 c4^\startTextSpan c c c \stopTextSpan
3167 Note that negative values move the text @emph{up}, contrary to the
3168 effect that might be expected, as a value of @w{@code{-1}} or
3169 @code{DOWN} means align the @emph{bottom} edge of the text with
3170 the spanner line. A value of @code{1} or @code{UP} aligns
3171 the top edge of the text with the spanner line.
3174 Setting this sub-property to @code{#t} produces an arrowhead at the
3178 This sub-property controls the space between the specified
3179 end point of the line and the actual end. Without padding, a
3180 glissando would start and end in the center of each note head.
3184 The music function @code{\endSpanners} terminates the spanner
3185 which starts on the immediately following note prematurely. It
3186 is terminated after exactly one note, or at the following bar line
3187 if @code{to-barline} is true and a bar line occurs before the next
3190 @lilypond[verbatim,quote,ragged-right,relative=2]
3192 c2 \startTextSpan c2 c2
3197 When using @code{\endSpanners} it is not necessary to close
3198 \startTextSpan with \stopTextSpan, nor is it necessary to close
3199 hairpins with @code{\!}.
3202 Internals Reference:
3203 @rinternals{TextSpanner},
3204 @rinternals{Glissando},
3205 @rinternals{VoiceFollower},
3206 @rinternals{TrillSpanner},
3207 @rinternals{line-spanner-interface}.
3210 @node Visibility of objects
3211 @subsection Visibility of objects
3213 @cindex objects, visibility of
3214 @cindex grobs, visibility of
3215 @cindex visibility of objects
3217 There are four main ways in which the visibility of layout objects
3218 can be controlled: their stencil can be removed, they can be made
3219 transparent, they can be colored white, or their
3220 @code{break-visibility} property can be overridden. The first
3221 three apply to all layout objects; the last to just a few -- the
3222 @emph{breakable} objects. The Learning Manual introduces these
3223 four techniques, see @rlearning{Visibility and color of objects}.
3225 There are also a few other techniques which are specific to
3226 certain layout objects. These are covered under Special
3230 * Removing the stencil::
3231 * Making objects transparent::
3232 * Painting objects white::
3233 * Using break-visibility::
3234 * Special considerations::
3238 @node Removing the stencil
3239 @unnumberedsubsubsec Removing the stencil
3241 @cindex stencil, removing
3244 Every layout object has a stencil property. By default this is set
3245 to the specific function which draws that object. If this property
3246 is overridden to @code{#f} no function will be called and the object
3247 will not be drawn. The default action can be recovered with
3250 @lilypond[quote,verbatim,relative=1]
3252 \override Score.BarLine.stencil = ##f
3254 \revert Score.BarLine.stencil
3258 This rather common operation has a shortcut @code{\omit}:
3260 @lilypond[quote,verbatim,relative=1]
3264 \undo \omit Score.BarLine
3268 @node Making objects transparent
3269 @unnumberedsubsubsec Making objects transparent
3271 @cindex transparent, making objects
3274 Every layout object has a transparent property which by default is
3275 set to @code{#f}. If set to @code{#t} the object still occupies
3276 space but is made invisible.
3278 @lilypond[quote,verbatim,relative=2]
3280 \once \override NoteHead.transparent = ##t
3284 This rather common operation has a shortcut @code{\hide}:
3286 @lilypond[quote,verbatim,relative=2]
3288 \once \hide NoteHead
3292 @node Painting objects white
3293 @unnumberedsubsubsec Painting objects white
3295 @cindex objects, coloring
3296 @cindex coloring objects
3298 @cindex printing order
3299 @cindex overwriting objects
3300 @cindex objects, overwriting
3301 @cindex grobs, overwriting
3303 Every layout object has a color property which by default is set
3304 to @code{black}. If this is overridden to @code{white} the object
3305 will be indistinguishable from the white background. However,
3306 if the object crosses other objects the color of the crossing
3307 points will be determined by the order in which they are drawn,
3308 and this may leave a ghostly image of the white object, as shown
3311 @lilypond[quote,verbatim,relative=2]
3312 \override Staff.Clef.color = #white
3316 This may be avoided by changing the order of printing the objects.
3317 All layout objects have a @code{layer} property which should be set
3318 to an integer. Objects with the lowest value of @code{layer} are
3319 drawn first, then objects with progressively higher values are drawn,
3320 so objects with higher values overwrite objects with lower values.
3321 By default most objects are assigned a @code{layer} value of
3322 @code{1}, although a few objects, including @code{StaffSymbol} and
3323 @code{BarLine}, are assigned a value of @code{0}. The order of
3324 printing objects with the same value of @code{layer} is indeterminate.
3326 In the example above the white clef, with a default @code{layer}
3327 value of @code{1}, is drawn after the staff lines (default
3328 @code{layer} value @code{0}), so overwriting them. To change this,
3329 the @code{Clef} object must be given in a lower value of
3330 @code{layer}, say @w{@code{-1}}, so that it is drawn earlier:
3332 @lilypond[quote,verbatim,relative=2]
3333 \override Staff.Clef.color = #white
3334 \override Staff.Clef.layer = #-1
3338 @node Using break-visibility
3339 @unnumberedsubsubsec Using break-visibility
3341 @c TODO Add making other objects breakable
3343 @cindex break-visibility
3345 Most layout objects are printed only once, but some like
3346 bar lines, clefs, time signatures and key signatures, may need
3347 to be printed twice when a line break occurs -- once at the end
3348 of the line and again at the start of the next line. Such
3349 objects are called @emph{breakable}, and have a property, the
3350 @code{break-visibility} property to control their visibility
3351 at the three positions in which they may appear -- at the
3352 start of a line, within a line if they are changed, and at the
3353 end of a line if a change takes place there.
3355 For example, the time signature
3356 by default will be printed at the start of the first line, but
3357 nowhere else unless it changes, when it will be printed at the
3358 point at which the change occurs. If this change occurs at the
3359 end of a line the new time signature will be printed at the start
3360 of the next line and a cautionary time signature will be printed
3361 at the end of the previous line as well.
3363 This behaviour is controlled by the @code{break-visibility}
3364 property, which is explained in
3365 @c Leave this ref on a newline - formats incorrectly otherwise -td
3366 @rlearning{Visibility and color of objects}. This property takes
3367 a vector of three booleans which, in order, determine whether the
3368 object is printed at the end of, within the body of, or at the
3369 beginning of a line. Or to be more precise, before a line break,
3370 where there is no line break, or after a line break.
3372 Alternatively, these eight combinations may be specified
3373 by pre-defined functions, defined in @file{scm/output-lib.scm},
3374 where the last three columns indicate whether the layout objects
3375 will be visible in the positions shown at the head of the columns:
3377 @multitable {@code{begin-of-line-invisible}} {@code{#(#t #t #t)}} {Before} {At no} {After}
3378 @headitem Function @tab Vector @tab Before @tab At no @tab After
3379 @headitem form @tab form @tab break @tab break @tab break
3381 @item @code{all-visible} @tab @code{#(#t #t #t)} @tab yes @tab yes @tab yes
3382 @item @code{begin-of-line-visible} @tab @code{#(#f #f #t)} @tab no @tab no @tab yes
3383 @item @code{center-visible} @tab @code{#(#f #t #f)} @tab no @tab yes @tab no
3384 @item @code{end-of-line-visible} @tab @code{#(#t #f #f)} @tab yes @tab no @tab no
3385 @item @code{begin-of-line-invisible} @tab @code{#(#t #t #f)} @tab yes @tab yes @tab no
3386 @item @code{center-invisible} @tab @code{#(#t #f #t)} @tab yes @tab no @tab yes
3387 @item @code{end-of-line-invisible} @tab @code{#(#f #t #t)} @tab no @tab yes @tab yes
3388 @item @code{all-invisible} @tab @code{#(#f #f #f)} @tab no @tab no @tab no
3391 The default settings of @code{break-visibility} depend on the
3392 layout object. The following table shows all the layout objects
3393 of interest which are affected by @code{break-visibility} and the
3394 default setting of this property:
3396 @multitable @columnfractions .3 .3 .4
3398 @headitem Layout object @tab Usual context @tab Default setting
3400 @c omit Ambitus as it appears not to be affected by break-visibility -td
3401 @c @item @code{Ambitus} @tab as specified @tab @code{begin-of-line-visible}
3402 @item @code{BarLine} @tab @code{Score} @tab calculated
3403 @item @code{BarNumber} @tab @code{Score} @tab @code{begin-of-line-visible}
3404 @c omit the following item until it can be explained -td
3405 @c @item @code{BreakAlignGroup} @tab @code{Score} @tab calculated
3406 @item @code{BreathingSign} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3407 @item @code{Clef} @tab @code{Staff} @tab @code{begin-of-line-visible}
3408 @item @code{Custos} @tab @code{Staff} @tab @code{end-of-line-visible}
3409 @item @code{DoublePercentRepeat} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3410 @item @code{KeyCancellation} @tab @code{Staff} @tab @code{begin-of-line-invisible}
3411 @item @code{KeySignature} @tab @code{Staff} @tab @code{begin-of-line-visible}
3412 @c omit LeftEdge until it can be explained -td
3413 @c @item @code{LeftEdge} @tab @code{Score} @tab @code{center-invisible}
3414 @item @code{ClefModifier} @tab @code{Staff} @tab @code{begin-of-line-visible}
3415 @item @code{RehearsalMark} @tab @code{Score} @tab @code{end-of-line-invisible}
3416 @item @code{TimeSignature} @tab @code{Staff} @tab @code{all-visible}
3420 The example below shows the use of the vector form to control the
3421 visibility of bar lines:
3423 @lilypond[quote,verbatim,relative=1,ragged-right]
3426 % Remove bar line at the end of the current line
3427 \once \override Score.BarLine.break-visibility = ##(#f #t #t)
3433 Although all three components of the vector used to override
3434 @code{break-visibility} must be present, not all of them are
3435 effective with every layout object, and some combinations may
3436 even give errors. The following limitations apply:
3439 @item Bar lines cannot be printed at start of line.
3440 @item A bar number cannot be printed at the start of the first
3441 line unless it is set to be different from 1.
3442 @item Clef -- see below
3443 @item Double percent repeats are either all printed or all
3444 suppressed. Use begin-of line-invisible to print and
3445 all-invisible to suppress.
3446 @item Key signature -- see below
3447 @item ClefModifier -- see below
3450 @node Special considerations
3451 @unnumberedsubsubsec Special considerations
3453 @subsubsubheading Visibility following explicit changes
3455 @cindex key signature, visibility following explicit change
3456 @cindex explicitKeySignatureVisibility
3457 @cindex clef, visibility following explicit change
3458 @cindex explicitClefVisibility
3460 The @code{break-visibility} property controls the visibility of
3461 key signatures and changes of clef only at the start of lines,
3462 i.e. after a break. It has no effect on the visibility of the
3463 key signature or clef following an explicit key change or an
3464 explicit clef change within or at the end of a line. In the
3465 following example the key signature following the explicit change
3466 to B-flat major is still visible, even though @code{all-invisible}
3469 @lilypond[quote,verbatim,relative=1,ragged-right]
3472 % Try to remove all key signatures
3473 \override Staff.KeySignature.break-visibility = #all-invisible
3481 The visibility of such explicit key signature and clef changes is
3482 controlled by the @code{explicitKeySignatureVisibility} and
3483 @code{explicitClefVisibility} properties. These are the equivalent
3484 of the @code{break-visibility} property and both take a vector of
3485 three booleans or the predefined functions listed above, exactly like
3486 @code{break-visibility}. Both are properties of the Staff context,
3487 not the layout objects themselves, and so they are set using the
3488 @code{\set} command. Both are set by default to @code{all-visible}.
3489 These properties control only the visibility of key signatures and
3490 clefs resulting from explicit changes and do not affect key
3491 signatures and clefs at the beginning of lines;
3492 @code{break-visibility} must still be overridden in the appropriate
3493 object to remove these.
3495 @lilypond[quote,verbatim,relative=1,ragged-right]
3498 \set Staff.explicitKeySignatureVisibility = #all-invisible
3499 \override Staff.KeySignature.break-visibility = #all-invisible
3506 @subsubsubheading Visibility of cancelling accidentals
3508 To remove the cancelling accidentals printed at an explicit key
3509 change, set the Staff context property @code{printKeyCancellation}
3512 @lilypond[quote,verbatim,relative=1,ragged-right]
3515 \set Staff.explicitKeySignatureVisibility = #all-invisible
3516 \set Staff.printKeyCancellation = ##f
3517 \override Staff.KeySignature.break-visibility = #all-invisible
3524 With these overrides only the accidentals before the notes remain
3525 to indicate the change of key.
3527 Note that when changing the key to C@tie{}major or A@tie{}minor
3528 the cancelling accidentals would be the @emph{only} indication of
3529 the key change. In this case setting @code{printKeyCancellation} to
3530 @code{#f} has no effect:
3532 @lilypond[quote,verbatim,relative=1,ragged-right]
3535 \set Staff.explicitKeySignatureVisibility = #all-invisible
3536 \set Staff.printKeyCancellation = ##f
3543 To suppress the cancelling accidentals even when the key is
3544 changed to C@tie{}major or A@tie{}minor, override
3545 the visibility of the @code{KeyCancellation} grob instead:
3547 @lilypond[quote,verbatim,relative=1,ragged-right]
3550 \set Staff.explicitKeySignatureVisibility = #all-invisible
3551 \override Staff.KeyCancellation.break-visibility = #all-invisible
3558 @c TODO Add visibility of cautionary accidentals before notes
3560 @subsubsubheading Automatic bars
3562 @cindex automaticBars
3563 @cindex bar lines, suppressing
3565 As a special case, the printing of bar lines can also be turned off
3566 by setting the @code{automaticBars} property in the Score context.
3567 If set to @code{#f}, bar lines will not be printed automatically;
3568 they must be explicitly created with a @code{\bar} command. Unlike
3569 the @code{\cadenzaOn} predefined command, measures are still counted.
3570 Bar generation will resume according to that count if this property
3571 is later set to @code{#t}. When set to @code{#f}, line breaks can
3572 occur only at explicit @code{\bar} commands.
3576 @subsubsubheading Transposed clefs
3578 @cindex transposed clefs, visibility of
3579 @cindex visibility of transposed clefs
3580 @cindex clefs, visibility of transposition
3582 The small transposition symbol on transposed clefs is produced by the
3583 @code{ClefModifier} layout object. Its visibility is automatically
3584 inherited from the @code{Clef} object, so it is not necessary to apply
3585 any required @code{break-visibility} overrides to the @code{ClefModifier}
3586 layout objects to suppress transposition symbols for invisible clefs.
3588 For explicit clef changes, the @code{explicitClefVisibility}
3589 property controls both the clef symbol and any transposition symbol
3594 @rlearning{Visibility and color of objects}.
3598 @subsection Line styles
3600 Some performance indications, e.g., @i{rallentando} and
3601 @i{accelerando} and @i{trills} are written as text and are
3602 extended over many measures with lines, sometimes dotted or wavy.
3604 These all use the same routines as the glissando for drawing the
3605 texts and the lines, and tuning their behavior is therefore also
3606 done in the same way. It is done with a spanner, and the routine
3607 responsible for drawing the spanners is
3608 @code{ly:line-spanner::print}. This routine determines the
3609 exact location of the two @i{span points} and draws a line
3610 between them, in the style requested.
3612 Here is an example showing the different line styles available,
3613 and how to tune them.
3615 @lilypond[relative=2,ragged-right,verbatim,quote]
3617 \once \override Glissando.style = #'dashed-line
3619 \override Glissando.style = #'dotted-line
3621 \override Glissando.style = #'zigzag
3623 \override Glissando.style = #'trill
3627 The locations of the end-points of the spanner are computed
3628 on-the-fly for every graphic object, but it is possible to
3632 @lilypond[relative=2,ragged-right,verbatim,quote]
3634 \once \override Glissando.bound-details.right.Y = #-2
3638 The value for @code{Y} is set to @w{@code{-2}} for the right end
3639 point. The left side may be similarly adjusted by specifying
3640 @code{left} instead of @code{right}.
3642 If @code{Y} is not set, the value is computed from the vertical
3643 position of the left and right attachment points of the spanner.
3645 Other adjustments of spanners are possible, for details, see
3648 @node Rotating objects
3649 @subsection Rotating objects
3651 Both layout objects and elements of markup text can be rotated by
3652 any angle about any point, but the method of doing so differs.
3655 * Rotating layout objects::
3659 @node Rotating layout objects
3660 @unnumberedsubsubsec Rotating layout objects
3662 @cindex rotating objects
3663 @cindex objects, rotating
3665 All layout objects which support the @code{grob-interface} can be
3666 rotated by setting their @code{rotation} property. This takes a
3667 list of three items: the angle of rotation counter-clockwise,
3668 and the x and y coordinates of the point relative to the object's
3669 reference point about which the rotation is to be performed. The
3670 angle of rotation is specified in degrees and the coordinates in
3673 The angle of rotation and the coordinates of the rotation point must
3674 be determined by trial and error.
3676 @cindex hairpins, angled
3677 @cindex angled hairpins
3679 There are only a few situations where the rotation of layout
3680 objects is useful; the following example shows one situation where
3683 @lilypond[quote,verbatim,relative=1]
3685 \override Hairpin.rotation = #'(20 -1 0)
3689 @node Rotating markup
3690 @unnumberedsubsubsec Rotating markup
3692 All markup text can be rotated to lie at any angle by prefixing it
3693 with the @code{\rotate} command. The command takes two arguments:
3694 the angle of rotation in degrees counter-clockwise and the text to
3695 be rotated. The extents of the text are not rotated: they take
3696 their values from the extremes of the x and y coordinates of the
3697 rotated text. In the following example the
3698 @code{outside-staff-priority} property for text is set to @code{#f}
3699 to disable the automatic collision avoidance, which would push some
3700 of the text too high.
3702 @lilypond[quote,verbatim,relative=1]
3703 \override TextScript.outside-staff-priority = ##f
3704 g4^\markup { \rotate #30 "a G" }
3705 b^\markup { \rotate #30 "a B" }
3706 des^\markup { \rotate #30 "a D-Flat" }
3707 fis^\markup { \rotate #30 "an F-Sharp" }
3710 @node Advanced tweaks
3711 @section Advanced tweaks
3713 This section discusses various approaches to fine tuning the
3714 appearance of the printed score.
3717 * Aligning objects::
3718 * Vertical grouping of grobs::
3719 * Modifying stencils::
3720 * Modifying shapes::
3721 * Modifying broken spanners::
3722 * Unpure-pure containers::
3727 @rlearning{Tweaking output},
3728 @rlearning{Other sources of information}.
3731 @ref{Explaining the Internals Reference},
3732 @ref{Modifying properties}.
3735 @rextend{Interfaces for programmers}.
3738 @file{scm/define-grobs.scm}.
3741 @rlsr{Tweaks and overrides}.
3743 Internals Reference:
3744 @rinternals{All layout objects}.
3747 @node Aligning objects
3748 @subsection Aligning objects
3750 Graphical objects which support the @code{self-alignment-interface}
3751 and/or the @code{side-position-interface} can be aligned to a previously
3752 placed object in a variety of ways. For a list of these objects, see
3753 @rinternals{self-alignment-interface} and @rinternals{side-position-interface}.
3755 All graphical objects have a reference point, a horizontal extent and a
3756 vertical extent. The horizontal extent is a pair of numbers
3757 giving the displacements from the reference point of the left and
3758 right edges, displacements to the left being negative. The vertical
3759 extent is a pair of numbers giving the displacement from the reference
3760 point to the bottom and top edges, displacements down being negative.
3762 An object's position on a staff is given by the values of the
3763 @code{X-offset} and @code{Y-offset} properties. The value of
3764 @code{X-offset} gives the displacement from the X coordinate of
3765 the reference point of the parent object, and the value of
3766 @code{Y-offset} gives the displacement from the center line of the
3767 staff. The values of @code{X-offset} and @code{Y-offset} may
3768 be set directly or may be set to be calculated by procedures in order
3769 to achieve alignment with the parent object.
3771 @warning{Many objects have special positioning considerations which
3772 cause any setting of @code{X-offset} or @code{Y-offset} to be
3773 ignored or modified, even though the object supports the
3774 @code{self-alignment-interface}. Overriding the @code{X-offset}
3775 or @code{Y-offset} properties to a fixed value causes the respective
3776 @code{self-alignment} property to be disregarded.}
3778 For example, an accidental can be repositioned vertically by setting
3779 @code{Y-offset} but any changes to @code{X-offset} have no effect.
3781 Rehearsal marks may be aligned with breakable objects such as bar
3782 lines, clef symbols, time signature symbols and key signatures. There
3783 are special properties to be found in the @code{break-aligned-interface}
3784 for positioning rehearsal marks on such objects.
3788 @ref{Using the break-alignable-interface}.
3791 @rextend{Callback functions}.
3794 * Setting X-offset and Y-offset directly::
3795 * Using the side-position-interface::
3796 * Using the self-alignment-interface::
3797 * Using the break-alignable-interface::
3800 @node Setting X-offset and Y-offset directly
3801 @unnumberedsubsubsec Setting @code{X-offset} and @code{Y-offset} directly
3803 Numerical values may be given to the @code{X-offset} and @code{Y-offset}
3804 properties of many objects. The following example shows three
3805 notes with the default fingering position and the positions with @code{X-offset}
3806 and @code{Y-offset} modified.
3808 @lilypond[verbatim,quote,relative=2]
3815 -\tweak X-offset #-1
3822 @node Using the side-position-interface
3823 @unnumberedsubsubsec Using the @code{side-position-interface}
3825 An object which supports the @code{side-position-interface} can be
3826 placed next to its parent object so that
3827 the specified edges of the two objects touch. The object may be
3828 placed above, below, to the right or to the left of the parent.
3829 The parent cannot be specified; it is determined by the order of
3830 elements in the input stream. Most objects have the associated
3831 note head as their parent.
3833 The values of the @code{side-axis} and @code{direction} properties
3834 determine where the object is to be placed, as follows:
3836 @c TODO add an example of each to the table
3838 @multitable @columnfractions .3 .3 .3
3839 @headitem @code{side-axis} @tab @code{direction} @tab
3840 @headitem property @tab property @tab Placement
3842 @item @code{0} @tab @code{-1} @tab left
3843 @item @code{0} @tab @code{1} @tab right
3844 @item @code{1} @tab @code{-1} @tab below
3845 @item @code{1} @tab @code{1} @tab above
3849 When @code{side-axis} is @code{0}, @code{X-offset} should be set to
3850 the procedure @code{ly:side-position-interface::x-aligned-side}.
3851 This procedure will return the correct value of @code{X-offset} to
3852 place the object to the left or right side of the parent according
3853 to value of @code{direction}.
3855 When @code{side-axis} is @code{1}, @code{Y-offset} should be set to
3856 the procedure @code{ly:side-position-interface::y-aligned-side}.
3857 This procedure will return the correct value of @code{Y-offset} to
3858 place the object to the top or bottom of the parent according
3859 to value of @code{direction}.
3861 @c TODO Add examples
3863 @node Using the self-alignment-interface
3864 @unnumberedsubsubsec Using the @code{self-alignment-interface}
3866 @subsubsubheading Self-aligning objects horizontally
3868 The horizontal alignment of an object which supports the
3869 @code{self-alignment-interface} is controlled by the value of
3870 the @code{self-alignment-X} property, provided the object's
3871 @code{X-offset} property is set to
3872 @code{ly:self-alignment-interface::x-aligned-on-self}.
3873 @code{self-alignment-X} may be given any
3874 real value, in units of half the total X extent of the
3875 object. Negative values move the object to the right, positive
3876 to the left. A value of @code{0} centers the object on the
3877 reference point of its parent, a value of @w{@code{-1}} aligns the
3878 left edge of the object on the reference point of its parent,
3879 and a value of @code{1} aligns the right edge of the object on the
3880 reference point of its parent. The symbols @code{LEFT},
3881 @code{CENTER}, and @code{RIGHT} may be used instead of the values
3882 @w{@code{-1}}, @code{0}, and @code{1}, respectively.
3884 Normally the @code{\override} command would be used to modify the
3885 value of @code{self-alignment-X}, but the @code{\tweak} command
3886 can be used to separately align several annotations on a single
3889 @lilypond[quote,verbatim,relative=1]
3891 -\tweak self-alignment-X #-1
3893 -\tweak self-alignment-X #0
3895 -\tweak self-alignment-X #RIGHT
3897 -\tweak self-alignment-X #-2.5
3898 ^"aligned further to the right"
3901 @subsubsubheading Self-aligning objects vertically
3903 Objects may be aligned vertically in an analogous way to aligning
3904 them horizontally if the @code{Y-offset} property is set to
3905 @code{ly:self-alignment-interface::y-aligned-on-self}. However,
3906 other mechanisms are often involved in vertical alignment: the
3907 value of @code{Y-offset} is just one variable taken into account.
3908 This may make adjusting the value of some objects tricky.
3909 The units are just half the vertical extent of the object, which
3910 is usually quite small, so quite large numbers may be required.
3911 A value of @w{@code{-1}} aligns the lower edge of the object with
3912 the reference point of the parent object, a value of @code{0}
3913 aligns the center of the object with the reference point of the
3914 parent, and a value of @code{1} aligns the top edge of the object
3915 with the reference point of the parent. The symbols @code{DOWN},
3916 @code{CENTER}, and @code{UP} may be substituted for @w{@code{-1}},
3917 @code{0}, and @code{1}, respectively.
3919 @subsubsubheading Self-aligning objects in both directions
3921 By setting both @code{X-offset} and @code{Y-offset}, an object may
3922 be aligned in both directions simultaneously.
3924 The following example shows how to adjust a fingering mark so
3925 that it nestles close to the note head.
3927 @lilypond[quote,verbatim,relative=2]
3929 -\tweak self-alignment-X #0.5 % move horizontally left
3930 -\tweak Y-offset #ly:self-alignment-interface::y-aligned-on-self
3931 -\tweak self-alignment-Y #-1 % move vertically up
3936 @unnumberedsubsubsec Using the @code{aligned-on-parent} procedures
3938 @c Cannot document as they do not seem to operate consistently on all objects -td
3939 @c TODO investigate further
3941 The @code{aligned-on-parent} procedures are used in the same way
3942 as the @code{aligned-on-self} procedures, they difference being
3943 that they permit an object to be aligned with the @emph{edges} of
3944 the parent rather than the parent's reference point. The following
3945 example shows the difference:
3949 @lilypond[verbatim,quote]
3955 @unnumberedsubsubsec Using the @code{centered-on-parent} procedures
3957 @c Cannot document as they do not seem to operate consistently on all objects -td
3958 @c TODO investigate further
3962 @c TODO The align-interface, BassFigureAlignment and VerticalAlignment
3964 @node Using the break-alignable-interface
3965 @unnumberedsubsubsec Using the @code{break-alignable-interface}
3967 @cindex align to objects
3968 @cindex break-align-symbols
3970 Rehearsal marks and bar numbers may be aligned with notation
3971 objects other than bar lines. These objects include @code{ambitus},
3972 @code{breathing-sign}, @code{clef}, @code{custos}, @code{staff-bar},
3973 @code{left-edge}, @code{key-cancellation}, @code{key-signature}, and
3974 @code{time-signature}.
3976 Each type of object has its own default reference point, to which
3977 rehearsal marks are aligned:
3979 @lilypond[verbatim,quote,relative=1]
3980 % The rehearsal mark will be aligned to the right edge of the Clef
3981 \override Score.RehearsalMark.break-align-symbols = #'(clef)
3986 % The rehearsal mark will be aligned to the left edge of the Time Signature
3987 \override Score.RehearsalMark.break-align-symbols = #'(time-signature)
3993 % The rehearsal mark will be centered above the Breath Mark
3994 \override Score.RehearsalMark.break-align-symbols = #'(breathing-sign)
4003 A list of possible target alignment objects may be specified. If
4004 some of the objects are invisible at that point due to the setting
4005 of @code{break-visibility} or the explicit visibility settings for
4006 keys and clefs, the rehearsal mark or bar number is aligned to the
4007 first object in the list which is visible. If no objects in the
4008 list are visible the object is aligned to the bar line. If the bar
4009 line is invisible the object is aligned to the place where the bar
4012 @lilypond[verbatim,quote,relative=1]
4013 % The rehearsal mark will be aligned to the right edge of the Key Signature
4014 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4019 % The rehearsal mark will be aligned to the right edge of the Clef
4020 \set Staff.explicitKeySignatureVisibility = #all-invisible
4021 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4026 % The rehearsal mark will be centered above the Bar Line
4027 \set Staff.explicitKeySignatureVisibility = #all-invisible
4028 \set Staff.explicitClefVisibility = #all-invisible
4029 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4036 The alignment of the rehearsal mark relative to the notation object
4037 can be changed, as shown in the following example. In a score with
4038 multiple staves, this setting should be done for all the staves.
4040 @lilypond[verbatim,quote,relative=1]
4041 % The RehearsalMark will be aligned with the right edge of the Key Signature
4042 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4048 % The RehearsalMark will be centered above the Key Signature
4049 \once \override Score.KeySignature.break-align-anchor-alignment = #CENTER
4053 % The RehearsalMark will be aligned with the left edge of the Key Signature
4054 \once \override Score.KeySignature.break-align-anchor-alignment = #LEFT
4060 The rehearsal mark can also be offset to the right or left of the left
4061 edge by an arbitrary amount. The units are staff-spaces:
4063 @lilypond[verbatim,quote,relative=1]
4064 % The RehearsalMark will be aligned with the left edge of the Key Signature
4065 % and then shifted right by 3.5 staff-spaces
4066 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4067 \once \override Score.KeySignature.break-align-anchor = #3.5
4071 % The RehearsalMark will be aligned with the left edge of the Key Signature
4072 % and then shifted left by 2 staff-spaces
4073 \once \override Score.KeySignature.break-align-anchor = #-2
4080 @node Vertical grouping of grobs
4081 @subsection Vertical grouping of grobs
4083 @c TODO Expand this section
4085 The VerticalAlignment and VerticalAxisGroup grobs work together.
4086 VerticalAxisGroup groups together different grobs like Staff, Lyrics,
4087 etc. VerticalAlignment then vertically aligns the different grobs
4088 grouped together by VerticalAxisGroup. There is usually only one
4089 VerticalAlignment per score but every Staff, Lyrics, etc. has its own
4093 @node Modifying stencils
4094 @subsection Modifying stencils
4096 All layout objects have a @code{stencil} property which is part of
4097 the @code{grob-interface}. By default, this property is usually
4098 set to a function specific to the object that is tailor-made to
4099 render the symbol which represents it in the output. For example,
4100 the standard setting for the @code{stencil} property of the
4101 @code{MultiMeasureRest} object is @code{ly:multi-measure-rest::print}.
4103 The standard symbol for any object can be replaced by modifying the
4104 @code{stencil} property to reference a different, specially-written,
4105 procedure. This requires a high level of knowledge of the internal
4106 workings of LilyPond, but there is an easier way which can often
4107 produce adequate results.
4109 This is to set the @code{stencil} property to the procedure which
4110 prints text -- @code{ly:text-interface::print} -- and to add a
4111 @code{text} property to the object which is set to contain the
4112 markup text which produces the required symbol. Due to the
4113 flexibility of markup, much can be achieved -- see in particular
4114 @ref{Graphic notation inside markup}.
4116 The following example demonstrates this by changing the note head
4117 symbol to a cross within a circle.
4119 @lilypond[verbatim,quote]
4121 \once \override NoteHead.stencil = #ly:text-interface::print
4122 \once \override NoteHead.text = \markup {
4124 \halign #-0.7 \draw-circle #0.85 #0.2 ##f
4125 \musicglyph #"noteheads.s2cross"
4133 Any of the glyphs in the feta Font can be supplied to the
4134 @code{\musicglyph} markup command -- see @ref{The Feta font}.
4136 @c TODO Add inserting eps files or ref to later
4138 @c TODO Add inserting Postscript or ref to later
4142 @ref{Graphic notation inside markup},
4143 @ref{Formatting text},
4144 @ref{Text markup commands},
4145 @ref{The Feta font}.
4148 @node Modifying shapes
4149 @subsection Modifying shapes
4152 * Modifying ties and slurs::
4155 @node Modifying ties and slurs
4156 @unnumberedsubsubsec Modifying ties and slurs
4158 @cindex slurs, modifying
4159 @cindex ties, modifying
4160 @cindex Bézier curves, control points
4161 @cindex control points, Bézier curves
4163 @code{Tie}s, @code{Slur}s, @code{PhrasingSlur}s,
4164 @code{LaissezVibrerTie}s and @code{RepeatTie}s are all drawn as
4165 third-order Bézier curves. If the shape of the tie or slur which
4166 is calculated automatically is not optimum, the shape may be
4167 modified manually in two ways:
4171 by specifying the displacements to be made to the control points
4172 of the automatically calculated Bézier curve, or
4175 by explicitly specifying the positions of the four control points
4176 required to define the wanted curve.
4179 Both methods are explained below. The first method is more suitable
4180 if only slight adjustments to the curve are required; the second may
4181 be better for creating curves which are related to just a single
4184 @subsubsubheading Cubic Bézier curves
4186 Third-order or cubic Bézier curves are defined by four control
4187 points. The first and fourth control points are precisely the
4188 starting and ending points of the curve. The intermediate two
4189 control points define the shape. Animations showing how the curve
4190 is drawn can be found on the web, but the following description
4191 may be helpful. The curve starts from the first control point
4192 heading directly towards the second, gradually bending over to
4193 head towards the third and continuing to bend over to head towards
4194 the fourth, arriving there travelling directly from the third
4195 control point. The curve is entirely contained in the
4196 quadrilateral defined by the four control points. Translations,
4197 rotations and scaling of the control points all result in exactly
4198 the same operations on the curve.
4200 @subsubsubheading Specifying displacements from current control points
4202 @cindex shaping slurs and ties
4205 In this example the automatic placement of the tie is not optimum,
4206 and @code{\tieDown} would not help.
4208 @lilypond[verbatim,quote,relative=1]
4212 { r4 <g c,> <g c,> <g c,> }
4216 Adjusting the control points of the tie with @code{\shape} allows
4217 the collisions to be avoided.
4219 The syntax of @code{\shape} is
4222 [-]@code{\shape} @var{displacements} @var{item}
4225 This will reposition the control-points of @var{item} by the amounts
4226 given by @var{displacements}. The @var{displacements} argument is a
4227 list of number pairs or a list of such lists. Each element of a pair
4228 represents the displacement of one of the coordinates of a
4229 control-point. If @var{item} is a string, the result is
4230 @code{\once\override} for the specified grob type. If @var{item} is
4231 a music expression, the result is the same music expression with an
4232 appropriate tweak applied.
4234 In other words, the @code{\shape} function can act as either a
4235 @code{\once\override} command or a @code{\tweak} command depending
4236 on whether the @var{item} argument is a grob name, like @qq{Slur},
4237 or a music expression, like @qq{(}. The @var{displacements} argument
4238 specifies the displacements of the four control points as a list of
4239 four pairs of (dx . dy) values in units of staff-spaces (or a list
4240 of such lists if the curve has more than one segment).
4242 The leading hyphen is required if and only if the @code{\tweak} form
4245 So, using the same example as above and the @code{\once\override}
4246 form of @code{\shape}, this will raise the tie by half a staff-space:
4248 @lilypond[verbatim,quote,relative=1]
4251 \shape #'((0 . 0.5) (0 . 0.5) (0 . 0.5) (0 . 0.5)) Tie
4255 { r4 <g c,> <g c,> <g c,> }
4259 This positioning of the tie is better, but maybe it should be raised
4260 more in the center. The following example does this, this time using
4261 the alternative @code{\tweak} form:
4263 @lilypond[verbatim,quote,relative=1]
4266 e1-\shape #'((0 . 0.5) (0 . 1) (0 . 1) (0 . 0.5)) ~ e
4269 { r4 <g c,> <g c,> <g c,> }
4273 Changes to the horizontal positions of the control points may be made
4274 in the same way, and two different curves starting at the same
4275 musical moment may also be shaped:
4277 @lilypond[verbatim,quote,ragged-right,relative=2]
4279 \shape #'((0.7 . -0.4) (0.5 . -0.4) (0.3 . -0.3) (0 . -0.2)) Slur
4280 \shape #'((0 . 0) (0 . 0.5) (0 . 0.5) (0 . 0)) PhrasingSlur
4284 The @code{\shape} function can also displace the control points of
4285 curves which stretch across line breaks. Each piece of the broken
4286 curve can be given its own list of offsets. If changes to a
4287 particular segment are not needed, the empty list can serve as a
4288 placeholder. In this example the line break makes the single slur
4291 @lilypond[verbatim,quote,ragged-right,relative=1]
4297 Changing the shapes of the two halves of the slur makes it clearer
4298 that the slur continues over the line break:
4300 @lilypond[verbatim,quote,ragged-right,relative=1]
4301 % () may be used as a shorthand for ((0 . 0) (0 . 0) (0 . 0) (0 . 0))
4302 % if any of the segments does not need to be changed
4304 (( 0 . 0) (0 . 0) (0 . 0) (0 . 1))
4305 ((0.5 . 1.5) (1 . 0) (0 . 0) (0 . -1.5))
4312 If an S-shaped curve is required the control points must always be
4313 adjusted manually --- LilyPond will never select such shapes
4316 @lilypond[verbatim,quote,relative=2]
4317 c8( e b-> f d' a e-> g)
4318 \shape #'((0 . -1) (5.5 . -0.5) (-5.5 . -10.5) (0 . -5.5)) PhrasingSlur
4319 c8\( e b-> f d' a e-> g\)
4322 @subsubsubheading Specifying control points explicitly
4324 The coordinates of the Bézier control points are specified in units
4325 of staff-spaces. The X@tie{}coordinate is relative to the reference
4326 point of the note to which the tie or slur is attached, and the
4327 Y@tie{}coordinate is relative to the staff center line. The
4328 coordinates are specified as a list of four pairs of decimal numbers
4329 (reals). One approach is to estimate the coordinates of the two
4330 end points, and then guess the two intermediate points. The optimum
4331 values are then found by trial and error. Be aware that these values
4332 may need to be manually adjusted if any further changes are made to
4333 the music or the layout.
4335 One situation where specifying the control points explicitly is
4336 preferable to specifying displacements is when they need to be
4337 specified relative to a single note. Here is an example of this.
4338 It shows one way of indicating a slur extending into alternative
4339 sections of a volta repeat.
4341 @lilypond[verbatim,quote,relative=2]
4343 \repeat volta 3 { c4 d( e f }
4348 % create a slur and move it to a new position
4349 % the <> is just an empty chord to carry the slur termination
4350 -\tweak control-points #'((-2 . 3.8) (-1 . 3.9) (0 . 4) (1 . 3.4)) ( <> )
4355 % create a slur and move it to a new position
4356 -\tweak control-points #'((-2 . 3) (-1 . 3.1) (0 . 3.2) (1 . 2.4)) ( <> )
4363 It is not possible to modify shapes of ties or slurs by changing
4364 the @code{control-points} property if there are multiple ties or slurs
4365 at the same musical moment -- the @code{\tweak} command will also not
4366 work in this case. However, the @code{tie-configuration} property of
4367 @code{TieColumn} can be overridden to set start line and direction as
4371 Internals Reference:
4372 @rinternals{TieColumn}.
4375 @node Modifying broken spanners
4376 @subsection Modifying broken spanners
4379 * Using alterBroken::
4382 @node Using alterBroken
4383 @unnumberedsubsubsec Using @code{\alterBroken}
4385 @cindex spanners, modifying
4386 @cindex broken spanners, modifying
4387 @funindex \alterBroken
4389 When a spanner crosses a line break or breaks, each piece
4390 inherits the attributes of the original spanner. Thus, ordinary
4391 tweaking of a broken spanner applies the same modifications to
4392 each of its segments. In the example below, overriding
4393 @code{thickness} affects the slur on either side of the line
4396 @lilypond[verbatim,quote,ragged-right,relative=2]
4398 \once\override Slur.thickness = 10
4404 Independently modifying the appearance of individual pieces
4405 of a broken spanner is possible with the @code{\alterBroken}
4406 command. This command can produce either an @code{\override}
4407 or a @code{\tweak} of a spanner property.
4409 The syntax for @code{\alterBroken} is
4412 [-]@code{\alterBroken} @var{property} @var{values} @var{item}
4415 The argument @var{values} is a list of values, one for each
4416 broken piece. If @var{item} is a grob name like @code{Slur} or
4417 @code{Staff.PianoPedalBracket}, the result is an @code{\override}
4418 of the specified grob type. If @var{item} is a music expression
4419 such as @qq{(} or @qq{[} the result is the same music expression
4420 with an appropriate tweak applied.
4422 The leading hyphen must be used with the @code{\tweak} form. Do
4423 not add it when @code{\alterBroken} is used as an
4426 In its @code{\override} usage, @code{\alterBroken} may be
4427 prefaced by @code{\once} or @code{\temporary} and reverted by
4428 using @code{\revert} with @var{property}.
4430 The following code applies an independent @code{\override} to
4431 each of the slur segments in the previous example:
4433 @lilypond[verbatim,quote,ragged-right,relative=2]
4435 \alterBroken thickness #'(10 1) Slur
4441 The @code{\alterBroken} command may be used with any spanner
4442 object, including @code{Tie}, @code{PhrasingSlur}, @code{Beam}
4443 and @code{TextSpanner}. For example, an editor preparing a
4444 scholarly edition may wish to indicate the absence of part of a
4445 phrasing slur in a source by dashing only the segment which has
4446 been added. The following example illustrates how this can be
4447 done, in this case using the @code{\tweak} form of the command:
4449 @lilypond[verbatim,quote,ragged-right,relative=2]
4450 % The empty list is conveniently used below, because it is the
4451 % default setting of dash-definition, resulting in a solid curve.
4452 c2-\alterBroken dash-definition #'(() ((0 1.0 0.4 0.75))) \(e
4457 It is important to understand that @code{\alterBroken} will set
4458 each piece of a broken spanner to the corresponding value in
4459 @var{values}. When there are fewer values than pieces, any
4460 additional piece will be assigned the empty list. This may lead
4461 to undesired results if the layout property is not set to the
4462 empty list by default. In such cases, each segment should be
4463 assigned an appropriate value.
4466 Line breaks may occur in different places following changes in
4467 layout. Settings chosen for @code{\alterBroken} may be unsuitable
4468 for a spanner that is no longer broken or is split into more
4469 segments than before. Explicit use of @code{\break} can guard
4470 against this situation.
4472 The @code{\alterBroken} command is ineffective for spanner
4473 properties accessed before line-breaking such as
4478 @rextend{Difficult tweaks}.
4481 @node Unpure-pure containers
4482 @subsection Unpure-pure containers
4484 @cindex Scheme, pure containers
4485 @cindex Scheme, unpure containers
4486 @cindex pure containers, Scheme
4487 @cindex unpure containers, Scheme
4488 @cindex horizontal spacing, overriding
4490 Unpure-pure containers are useful for overriding @emph{Y-axis} spacing
4491 calculations - specifically @code{Y-offset} and @code{Y-extent} - with a
4492 Scheme function instead of a literal (i.e. a number or pair).
4494 For certain grobs, the @code{Y-extent} is based on the @code{stencil}
4495 property, overriding the stencil property of one of these will
4496 require an additional @code{Y-extent} override with an unpure-pure
4497 container. When a function overrides a @code{Y-offset} and/or
4498 @code{Y-extent} it is assumed that this will trigger line breaking
4499 calculations too early during compilation. So the function is not
4500 evaluated at all (usually returning a value of @samp{0} or
4501 @samp{'(0 . 0)}) which can result in collisions. A @q{pure} function
4502 will not affect properties, objects or grob suicides and therefore will
4503 always have its Y-axis-related evaluated correctly.
4505 Currently, there are about thirty functions that are already considered
4506 @q{pure} and Unpure-pure containers are a way to set functions not on
4507 this list as @q{pure}. The @q{pure} function is evaluated @emph{before}
4508 any line-breaking and so the horizontal spacing can be adjusted
4509 @q{in time}. The @q{unpure} function is then evaluated @emph{after}
4512 @warning{As it is difficult to always know which functions are on this
4513 list we recommend that any @q{pure} functions you create do not use
4514 @code{Beam} or @code{VerticalAlignment} grobs.}
4516 An unpure-pure container is constructed as follows;
4518 @code{(ly:make-unpure-pure-container f0 f1)}
4520 where @code{f0} is a function taking @var{n} arguments (@var{n >= 1})
4521 and the first argument must always be the grob. This is the function
4522 that gives the actual result. @var{f1} is the function being labeled
4523 as @q{pure} that takes @var{n + 2} arguments. Again, the first argument
4524 must always still be the grob but the second and third are @q{start}
4525 and @q{end} arguments.
4527 @var{start} and @var{end} are, for all intents and purposes, dummy
4528 values that only matter for @code{Spanners} (i.e @code{Hairpin} or
4529 @code{Beam}), that can return different height estimations based on a
4530 starting and ending column.
4532 The rest are the other arguments to the first function (which
4533 may be none if @var{n = 1}).
4535 The results of the second function are used as an approximation of the
4536 value needed which is then used by the first function to get the real
4537 value which is then used for fine-tuning much later during the spacing
4540 @lilypond[verbatim,quote,ragged-right]
4541 #(define (square-line-circle-space grob)
4542 (let* ((pitch (ly:event-property (ly:grob-property grob 'cause) 'pitch))
4543 (notename (ly:pitch-notename pitch)))
4544 (if (= 0 (modulo notename 2))
4545 (make-circle-stencil 0.5 0.0 #t)
4546 (make-filled-box-stencil '(0 . 1.0)
4549 squareLineCircleSpace = {
4550 \override NoteHead.stencil = #square-line-circle-space
4553 smartSquareLineCircleSpace = {
4554 \squareLineCircleSpace
4555 \override NoteHead.Y-extent =
4556 #(ly:make-unpure-pure-container
4557 ly:grob::stencil-height
4558 (lambda (grob start end) (ly:grob::stencil-height grob)))
4561 \new Voice \with { \remove "Stem_engraver" }
4563 \squareLineCircleSpace
4565 \smartSquareLineCircleSpace
4570 In the first measure, without the unpure-pure container, the spacing
4571 engine does not know the width of the note head and lets it collide with
4572 the accidentals. In the second measure, with unpure-pure containers,
4573 the spacing engine knows the width of the note heads and avoids the
4574 collision by lengthening the line accordingly.
4576 Usually for simple calculations nearly-identical functions for
4577 both the @q{unpure} and @q{pure} parts can be used, by only
4578 changing the number of arguments passed to, and the scope of, the
4579 function. This use case is frequent enough that
4580 @code{ly:make-unpure-pure-container} constructs such a second
4581 function by default when called with only one function argument.
4583 @warning{If a function is labeled as @q{pure} and it turns out not to
4584 be, the results can be unexpected.}
4587 @node Using music functions
4588 @section Using music functions
4590 @c TODO -- add @seealso, etc. to these subsections
4592 Where tweaks need to be reused with different music expressions,
4593 it is often convenient to make the tweak part of a @emph{music
4594 function}. In this section, we discuss only @emph{substitution}
4595 functions, where the object is to substitute a variable into a
4596 piece of LilyPond input code. Other more complex functions are
4597 described in @rextend{Music functions}.
4600 * Substitution function syntax::
4601 * Substitution function examples::
4604 @node Substitution function syntax
4605 @subsection Substitution function syntax
4607 Making a function that substitutes a variable into LilyPond
4608 code is easy. The general form of these functions is
4612 #(define-music-function
4613 (@var{arg1} @var{arg2} @dots{})
4614 (@var{type1?} @var{type2?} @dots{})
4616 @var{@dots{}music@dots{}}
4623 @multitable @columnfractions .33 .66
4624 @item @code{@var{argN}}
4625 @tab @var{n}th argument
4627 @item @code{@var{typeN?}}
4628 @tab a scheme @emph{type predicate} for which @code{@var{argN}}
4629 must return @code{#t}.
4631 @item @code{@var{@dots{}music@dots{}}}
4632 @tab normal LilyPond input, using @code{$} (in places where only
4633 Lilypond constructs are allowed) or @code{#} (to use it as a Scheme
4634 value or music function argument or music inside of music lists) to
4639 The list of type predicates is required. Some of the most common
4640 type predicates used in music functions are:
4644 cheap-list? @emph{(use instead of }@q{list?}@emph{ for faster processing)}
4656 For a list of available type predicates, see
4657 @ref{Predefined type predicates}. User-defined type predicates
4662 @ref{Predefined type predicates}.
4665 @rextend{Music functions}.
4668 @file{lily/music-scheme.cc},
4670 @file{scm/lily.scm}.
4673 @node Substitution function examples
4674 @subsection Substitution function examples
4676 This section introduces some substitution function examples.
4677 These are not intended to be exhaustive, but rather to demonstrate
4678 some of the possibilities of simple substitution functions.
4680 In the first example, a function is defined that simplifies
4681 setting the padding of a TextScript:
4683 @lilypond[quote,verbatim,ragged-right]
4685 #(define-music-function
4689 \once \override TextScript.padding = #padding
4693 c''4^"piu mosso" b a b
4695 c4^"piu mosso" b a b
4697 c4^"piu mosso" b a b
4701 In addition to numbers, we can use music expressions such
4702 as notes for arguments to music functions:
4704 @lilypond[quote,verbatim,ragged-right]
4706 #(define-music-function
4710 \tweak NoteHead.stencil #ly:text-interface::print
4711 \tweak NoteHead.text
4712 \markup \musicglyph #"custodes.mensural.u0"
4713 \tweak Stem.stencil ##f
4717 \relative { c'4 d e f \custosNote g }
4720 Substitution functions with multiple arguments can be defined:
4722 @lilypond[quote,verbatim,ragged-right]
4724 #(define-music-function
4728 \once \override Score.MetronomeMark.padding = #padding
4729 \tempo \markup { \bold #tempotext }
4733 \tempo \markup { "Low tempo" }
4735 \tempoPadded #4.0 "High tempo"
4740 @c TODO: add appropriate @@ref's here.