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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 c' @{
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 c'' { d4 d d d }
566 musicB = \relative c'' { g4 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 c'' { a4 a a a }
605 accompaniment = \relative c' { d4 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]
643 melody = \relative c'' {
649 accompaniment = \relative c' {
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 a4^"Thicker stems" a a a
892 \override Stem.thickness = #4.0
899 Directly setting a context property
901 @lilypond[quote,verbatim]
904 a4^"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 a4^"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 a4^"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 a4^"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 a4^"Thick stems" a a a
1038 Directly setting a context property
1040 @lilypond[quote,verbatim]
1045 a4^"Default font" a a a
1049 \new Staff \with { fontSize = #-4 }
1052 a4^"Smaller font" a a a
1061 A predefined command such as @code{\dynamicUp}
1063 @lilypond[quote,verbatim]
1069 a4^"Dynamics below" a a a
1074 \new Staff \with { \accidentalStyle dodecaphonic }
1076 \new Voice \with { \dynamicUp }
1079 a4^"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 a4 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]
1478 If you visit the documentation on fingering instructions (in
1479 @ref{Fingering instructions}), you will notice:
1484 Internals Reference: @rinternals{Fingering}.
1489 @c outdated info; probably will delete.
1491 This fragment points to two parts of the program reference: a page
1492 on @code{FingeringEvent} and one on @code{Fingering}.
1494 The page on @code{FingeringEvent} describes the properties of the music
1495 expression for the input @w{@code{-2}}. The page contains many links
1496 forward. For example, it says
1499 Accepted by: @rinternals{Fingering_engraver},
1503 That link brings us to the documentation for the Engraver, the
1507 This engraver creates the following layout objects: @rinternals{Fingering}.
1510 In other words, once the @code{FingeringEvent}s are interpreted, the
1511 @code{Fingering_engraver} plug-in will process them.
1515 @c I can't figure out what this is supposed to mean. -gp
1517 The @code{Fingering_engraver} is also listed to create
1518 @rinternals{Fingering} objects,
1520 @c old info? it doesn't make any sense to me with our current docs.
1522 second bit of information listed under @b{See also} in the Notation
1527 The programmer's reference is available as an HTML document. It is
1528 highly recommended that you read it in HTML form, either online or
1529 by downloading the HTML documentation. This section will be much more
1530 difficult to understand if you are using the
1534 Follow the link to @rinternals{Fingering}. At the top of the
1538 Fingering objects are created by: @rinternals{Fingering_engraver} and
1539 @rinternals{New_fingering_engraver}.
1542 By following related links inside the program reference, we can follow the
1543 flow of information within the program:
1547 @item @rinternals{Fingering}:
1548 @rinternals{Fingering} objects are created by:
1549 @rinternals{Fingering_engraver}
1551 @item @rinternals{Fingering_engraver}:
1552 Music types accepted: @rinternals{fingering-event}
1554 @item @rinternals{fingering-event}:
1555 Music event type @code{fingering-event} is in Music expressions named
1556 @rinternals{FingeringEvent}
1559 This path goes against the flow of information in the program: it
1560 starts from the output, and ends at the input event. You could
1561 also start at an input event, and read with the flow of
1562 information, eventually ending up at the output object(s).
1564 The program reference can also be browsed like a normal document. It
1565 contains chapters on
1567 @rinternals{Music definitions},
1570 @code{Music definitions}
1572 on @rinternals{Translation}, and the @rinternals{Backend}. Every
1573 chapter lists all the definitions used and all properties that may be
1577 @node Layout interfaces
1578 @subsection Layout interfaces
1580 @cindex interface, layout
1581 @cindex layout interface
1584 The HTML page that we found in the previous section describes the
1585 layout object called @rinternals{Fingering}. Such an object is a
1586 symbol within the score. It has properties that store numbers (like
1587 thicknesses and directions), but also pointers to related objects. A
1588 layout object is also called a @emph{Grob}, which is short for Graphical
1589 Object. For more details about Grobs, see @rinternals{grob-interface}.
1591 The page for @code{Fingering} lists the definitions for the
1592 @code{Fingering} object. For example, the page says
1595 @code{padding} (dimension, in staff space):
1601 which means that the number will be kept at a distance of at least 0.5
1605 Each layout object may have several functions as a notational or
1606 typographical element. For example, the Fingering object
1607 has the following aspects
1611 Its size is independent of the horizontal spacing, unlike slurs or beams.
1614 It is a piece of text. Granted, it is usually a very short text.
1617 That piece of text is typeset with a font, unlike slurs or beams.
1620 Horizontally, the center of the symbol should be aligned to the
1621 center of the note head.
1624 Vertically, the symbol is placed next to the note and the staff.
1627 The vertical position is also coordinated with other superscript
1628 and subscript symbols.
1631 Each of these aspects is captured in so-called @emph{interface}s,
1632 which are listed on the @rinternals{Fingering} page at the bottom
1635 This object supports the following interfaces:
1636 @rinternals{item-interface},
1637 @rinternals{self-alignment-interface},
1638 @rinternals{side-position-interface}, @rinternals{text-interface},
1639 @rinternals{text-script-interface}, @rinternals{font-interface},
1640 @rinternals{finger-interface}, and @rinternals{grob-interface}.
1643 Clicking any of the links will take you to the page of the respective
1644 object interface. Each interface has a number of properties. Some of
1645 them are not user-serviceable (@q{Internal properties}), but others
1648 We have been talking of @emph{the} @code{Fingering} object, but actually it
1649 does not amount to much. The initialization file (see
1650 @rlearning{Other sources of information})
1651 @file{scm/define-grobs.scm} shows the soul of the @q{object},
1656 (avoid-slur . around)
1657 (slur-padding . 0.2)
1658 (staff-padding . 0.5)
1659 (self-alignment-X . 0)
1660 (self-alignment-Y . 0)
1661 (script-priority . 100)
1662 (stencil . ,ly:text-interface::print)
1663 (direction . ,ly:script-interface::calc-direction)
1664 (font-encoding . fetaText)
1665 (font-size . -5) ; don't overlap when next to heads.
1666 (meta . ((class . Item)
1667 (interfaces . (finger-interface
1669 text-script-interface
1671 side-position-interface
1672 self-alignment-interface
1673 item-interface))))))
1677 As you can see, the @code{Fingering} object is nothing more than a
1678 bunch of variable settings, and the webpage in the Internals Reference
1679 is directly generated from this definition.
1682 @node Determining the grob property
1683 @subsection Determining the grob property
1685 @c TODO remove this (it's in the LM)
1686 @c Replace with more factual directions
1688 Recall that we wanted to change the position of the @b{2} in
1690 @lilypond[quote,relative=2,verbatim]
1696 Since the @b{2} is vertically positioned next to its note, we have to
1697 meddle with the interface associated with this positioning. This is
1698 done using @code{side-position-interface}. The page for this interface
1702 @code{side-position-interface}
1704 Position a victim object (this one) next to other objects (the
1705 support). The property @code{direction} signifies where to put the
1706 victim object relative to the support (left or right, up or down?)
1711 Below this description, the variable @code{padding} is described as
1716 (dimension, in staff space)
1718 Add this much extra space between objects that are next to each other.
1722 By increasing the value of @code{padding}, we can move the
1723 fingering away from the note head. The following command inserts
1724 3 staff spaces of white
1725 between the note and the fingering:
1727 \once \override Voice.Fingering.padding = #3
1730 Inserting this command before the Fingering object is created,
1731 i.e., before @code{c2}, yields the following result:
1733 @lilypond[quote,relative=2,verbatim]
1734 \once \override Voice.Fingering.padding = #3
1741 In this case, the context for this tweak is @code{Voice}. This
1742 fact can also be deduced from the program reference, for the page for
1743 the @rinternals{Fingering_engraver} plug-in says
1746 Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
1750 @node Naming conventions
1751 @subsection Naming conventions
1753 Another thing that is needed, is an overview of the various naming
1757 @item scheme functions: lowercase-with-hyphens (incl. one-word
1759 @item scheme functions: ly:plus-scheme-style
1760 @item music events, music classes and music properties:
1762 @item Grob interfaces: scheme-style
1763 @item backend properties: scheme-style (but X and Y!)
1764 @item contexts (and MusicExpressions and grobs): Capitalized or
1766 @item context properties: lowercaseFollowedByCamelCase
1768 Capitalized_followed_by_lowercase_and_with_underscores
1771 Questions to be answered:
1773 @item Which of these are conventions and which are rules?
1774 @item Which are rules of the underlying language, and which are
1778 @node Modifying properties
1779 @section Modifying properties
1781 @c TODO change the menu and subsection node names to use
1782 @c backslash once the new macro to handle the refs
1783 @c is available. Need to find and change all refs at
1784 @c the same time. -td
1787 * Overview of modifying properties::
1789 * The override command::
1790 * The tweak command::
1791 * set versus override::
1792 * Modifying alists::
1796 @node Overview of modifying properties
1797 @subsection Overview of modifying properties
1799 Each context is responsible for creating certain types of graphical
1800 objects. The settings used for printing these objects are also stored by
1801 context. By changing these settings, the appearance of objects can be
1804 There are two different kinds of properties stored in contexts:
1805 context properties and grob properties. Context properties are
1806 properties that apply to the context as a whole and control
1807 how the context itself is displayed. In contrast, grob properties
1808 apply to specific grob types that will be displayed in the context.
1810 The @code{\set} and @code{\unset} commands are used to change values
1811 for context properties. The @code{\override} and @code{\revert}
1812 commands are used to change values for grob properties.
1815 The syntax for this is
1818 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1821 Here @var{name} is the name of a graphical object, like
1822 @code{Stem} or @code{NoteHead}, and @var{property} is an internal
1823 variable of the formatting system (@q{grob property} or @q{layout
1824 property}). The latter is a symbol, so it must be quoted. The
1825 subsection @ref{Modifying properties}, explains what to fill in
1826 for @var{name}, @var{property}, and @var{value}. Here we only
1827 discuss the functionality of this command.
1832 \override Staff.Stem.thickness = #4.0
1836 makes stems thicker (the default is 1.3, with staff line thickness as a
1837 unit). Since the command specifies @code{Staff} as context, it only
1838 applies to the current staff. Other staves will keep their normal
1839 appearance. Here we see the command in action:
1841 @lilypond[quote,verbatim,relative=2]
1843 \override Staff.Stem.thickness = #4.0
1849 The @code{\override} command changes the definition of the @code{Stem}
1850 within the current @code{Staff}. After the command is interpreted
1851 all stems are thickened.
1853 Analogous to @code{\set}, the @var{context} argument may be left out,
1854 causing the default context @code{Voice} to be used. Adding
1855 @code{\once} applies the change during one timestep only.
1857 @lilypond[quote,verbatim,relative=2]
1859 \once \override Stem.thickness = #4.0
1864 The @code{\override} must be done before the object is
1865 started. Therefore, when altering @emph{Spanner} objects such as slurs
1866 or beams, the @code{\override} command must be executed at the moment
1867 when the object is created. In this example,
1869 @lilypond[quote,verbatim,relative=2]
1870 \override Slur.thickness = #3.0
1872 \override Beam.beam-thickness = #0.6
1877 the slur is fatter but the beam is not. This is because the command for
1878 @code{Beam} comes after the Beam is started, so it has no effect.
1880 Analogous to @code{\unset}, the @code{\revert} command for a context
1881 undoes an @code{\override} command; like with @code{\unset}, it only
1882 affects settings that were made in the same context. In other words, the
1883 @code{\revert} in the next example does not do anything.
1886 \override Voice.Stem.thickness = #4.0
1887 \revert Staff.Stem.thickness
1890 Some tweakable options are called @q{subproperties} and reside inside
1891 properties. To tweak those, use commands of the form
1893 @c leave this as a long long
1895 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
1902 \override Stem.details.beamed-lengths = #'(4 4 3)
1908 Internals Reference:
1909 @rinternals{Backend},
1910 @rinternals{All layout objects},
1911 @rinternals{OverrideProperty},
1912 @rinternals{RevertProperty},
1913 @rinternals{PropertySet}.
1916 The back-end is not very strict in type-checking object properties.
1917 Cyclic references in Scheme values for properties can cause hangs
1918 or crashes, or both.
1921 @node The set command
1922 @subsection The @code{@bs{}set} command
1926 @cindex changing properties
1928 Each context has a set of @emph{properties}, variables contained
1929 in that context. Context properties are changed with the @code{\set}
1930 command, which has the following syntax:
1933 \set @var{context}.@var{property} = #@var{value}
1936 @var{value} is a Scheme object, which is why it must be preceded by
1937 the @code{#}@tie{}character.
1939 Contexts properties are usually named in
1940 @code{studlyCaps}. They mostly control the translation from
1941 music to notation, e.g. @code{localAlterations} (for determining
1942 whether to print accidentals), or @code{measurePosition} (for
1943 determining when to print a bar line). Context properties can
1944 change value over time while interpreting a piece of music;
1945 @code{measurePosition} is an obvious example of
1946 this. Context properties are modified with @code{\set}.
1948 For example, multimeasure rests will be combined into a single bar
1949 if the context property @code{skipBars} is set to @code{#t}:
1951 @lilypond[quote,verbatim,relative=2]
1953 \set Score.skipBars = ##t
1957 If the @var{context} argument is left out, then the property will be
1958 set in the current bottom context (typically @code{ChordNames},
1959 @code{Voice}, @code{TabVoice}, or @code{Lyrics}).
1961 @lilypond[quote,verbatim,relative=2]
1962 \set Score.autoBeaming = ##f
1966 \set autoBeaming = ##t
1974 The change is applied @q{on-the-fly}, during the music, so that the
1975 setting only affects the second group of eighth notes.
1977 Note that the bottom-most context does not always contain the property
1978 that you wish to change -- for example, attempting to set the
1979 @code{skipBars} property of the default bottom context, in this case
1980 @code{Voice}, will have no effect, because skipBars is a property of
1981 the @code{Score} context.
1983 @lilypond[quote,verbatim,relative=2]
1989 Contexts are hierarchical, so if an enclosing context was specified, for
1990 example @code{Staff}, then the change would also apply to all
1991 @code{Voice}s in the current staff.
1995 The @code{\unset} command:
1998 \unset @var{context}.@var{property}
2002 is used to remove the definition of @var{property} from
2003 @var{context}. This command removes
2004 the definition only if it is set in @var{context}.
2005 Properties that have been set in enclosing contexts will
2006 not be altered by an unset in an enclosed context:
2008 @lilypond[quote,verbatim,relative=2]
2009 \set Score.autoBeaming = ##t
2014 \unset Score.autoBeaming
2022 Like @code{\set}, the @var{context} argument does not have to be
2023 specified for a bottom context, so the two statements
2026 \set Voice.autoBeaming = ##t
2027 \set autoBeaming = ##t
2031 are equivalent if the current bottom context is @code{Voice}.
2035 Preceding a @code{\set} command by @code{\once} makes the
2036 setting apply to only a single time-step:
2038 @lilypond[quote,verbatim,relative=2]
2040 \once \set fontSize = #4.7
2045 A full description of all available context properties is in the
2046 internals reference, see
2048 @rinternals{Tunable context properties}.
2051 Translation @expansion{} Tunable context properties.
2055 Internals Reference:
2056 @rinternals{Tunable context properties}.
2059 @node The override command
2060 @subsection The @code{\override} command
2062 @cindex grob properties
2063 @cindex properties, grob
2066 There is a special type of context property: the grob
2067 description. Grob descriptions are named in @code{StudlyCaps}
2068 (starting with capital letters). They contain the
2069 @q{default settings} for a particular kind of grob as an
2070 association list. See @file{scm/define-grobs.scm}
2071 to see the settings for each grob description. Grob descriptions
2072 are modified with @code{\override}.
2074 The syntax for the @code{\override} command is
2077 \override [@var{context}.]@var{GrobName}.@var{property} = #@var{value}
2080 For example, we can increase the thickness of a note stem by
2081 overriding the @code{thickness} property of the @code{Stem}
2084 @lilypond[quote,verbatim,relative=2]
2086 \override Voice.Stem.thickness = #3.0
2090 If no context is specified in an @code{\override}, the bottom
2093 @lilypond[quote,verbatim,relative=2]
2094 { \override Staff.Stem.thickness = #3.0
2098 \override Stem.thickness = #0.5
2107 Some tweakable options are called @q{subproperties} and reside inside
2108 properties. To tweak those, use commands in the form
2111 \override Stem.details.beamed-lengths = #'(4 4 3)
2114 or to modify the ends of spanners, use a form like these
2117 \override TextSpanner.bound-details.left.text = #"left text"
2118 \override TextSpanner.bound-details.right.text = #"right text"
2122 @cindex reverting overrides
2123 @cindex overrides, reverting
2125 The effects of @code{\override} can be undone by @code{\revert}.
2127 The syntax for the @code{\revert} command is
2130 \revert [@var{context}.]@var{GrobName}.@var{property}
2135 @lilypond[quote,verbatim,relative=2]
2137 \override Voice.Stem.thickness = #3.0
2139 \revert Voice.Stem.thickness
2143 The effects of @code{\override} and @code{\revert} apply to all
2144 grobs in the affected context from the current time forward:
2146 @lilypond[quote,verbatim,relative=2]
2151 \override Staff.Stem.thickness = #3.0
2155 \revert Staff.Stem.thickness
2163 @cindex overriding for only one moment
2165 @code{\once} can be used with @code{\override}
2166 to affect only the current time step:
2168 @lilypond[quote,verbatim,relative=2]
2172 \override Stem.thickness = #3.0
2176 \once \override Stem.thickness = #3.0
2185 Commands which change output generally look like
2188 \override Voice.Stem.thickness = #3.0
2192 To construct this tweak we must determine these bits of information:
2195 @item the context: here @code{Voice}.
2196 @item the layout object: here @code{Stem}.
2197 @item the layout property: here @code{thickness}.
2198 @item a sensible value: here @code{3.0}.
2201 @cindex internal documentation
2202 @cindex finding graphical objects
2203 @cindex graphical object descriptions
2206 @cindex internal documentation
2208 For many properties, regardless of the data type of the property, setting the
2209 property to false (@code{#f}) will result in turning it off, causing
2210 LilyPond to ignore that property entirely. This is particularly useful for
2211 turning off grob properties which may otherwise be causing problems.
2213 We demonstrate how to glean this information from the notation manual
2214 and the program reference.
2218 Internals Reference:
2219 @rinternals{Backend}
2222 @node The tweak command
2223 @subsection The @code{\tweak} command
2228 Changing grob properties
2229 with @code{\override} causes the changes to apply to all of the
2230 given grobs in the context at the moment the change applies.
2231 Sometimes, however, it is desirable to have changes apply to just
2232 one grob, rather than to all grobs in the affected context. This is
2233 accomplished with the @code{\tweak} command, which has the following
2237 \tweak [@var{layout-object}.]@var{grob-property} @var{value}
2240 Specifying @var{layout-object} is optional.
2241 The @code{\tweak} command applies to the music object that immediately
2242 follows @var{value} in the music stream.
2245 In some cases, it is possible to take a short-cut for tuning
2246 graphical objects. For objects that are created directly from
2247 an item in the input file, you can use the @code{\tweak} command.
2250 @lilypond[relative=2,verbatim,quote]
2255 \tweak duration-log #1
2264 The main use of the @code{\tweak} command is to modify just
2265 one of a number of notation elements which start at the same musical
2266 moment, like the notes of a chord, or tuplet brackets which start
2269 The @code{\tweak} command sets a property in the following object
2270 directly, without requiring the grob name or context to be
2271 specified. For this to work, it is necessary for the @code{\tweak}
2272 command to remain immediately adjacent to the object to which it is
2273 to apply after the input file has been converted to a music stream.
2274 This is often not the case, as many additional elements are inserted
2275 into the music stream implicitly. For example, when a note which is
2276 not part of a chord is processed, LilyPond implicitly inserts a
2277 @code{ChordEvent} event before the note, so separating the tweak
2278 from the note. However, if chord symbols are placed round the
2279 tweak and the note, the @code{\tweak} command comes after the
2280 @code{ChordEvent} in the music stream, so remaining adjacent to the
2281 note, and able to modify it.
2285 @lilypond[relative=2,verbatim,quote]
2286 <\tweak color #red c>4
2292 @lilypond[relative=2,verbatim,quote]
2293 \tweak color #red c4
2298 For an introduction to the syntax and uses of the tweak command
2299 see @rlearning{Tweaking methods}.
2301 When several similar items are placed at the same musical moment,
2302 the @code{\override} command cannot be used to modify just one of
2303 them -- this is where the @code{\tweak} command must be used.
2304 Items which may appear more than once at the same musical moment
2305 include the following:
2307 @c TODO expand to include any further uses of \tweak
2309 @item note heads of notes inside a chord
2310 @item articulation signs on a single note
2311 @item ties between notes in a chord
2312 @item tuplet brackets starting at the same time
2315 @c TODO add examples of these
2317 @cindex chord, modifying one note in
2319 In this example, the color of one note head and the type of another
2320 note head are modified within a single chord:
2322 @lilypond[relative=2,verbatim,quote]
2327 \tweak duration-log #1
2332 @code{\tweak} can be used to modify slurs:
2334 @lilypond[verbatim,quote,relative=1]
2335 c-\tweak thickness #5 ( d e f)
2339 For the @code{\tweak} command to work, it must
2340 remain immediately adjacent to the object to which it is
2341 to apply after the input file has been converted to a music stream.
2342 Tweaking a whole chord does not do anything since its music event
2343 only acts as a container, and all layout objects are created from events
2344 inside of the @code{EventChord}:
2346 @lilypond[relative=2,verbatim,quote]
2347 \tweak color #red c4
2348 \tweak color #red <c e>4
2349 <\tweak color #red c e>4
2352 The simple @code{\tweak} command cannot be used to modify any object
2353 that is not directly created from the input. In particular
2354 it will not affect stems, automatic
2355 beams or accidentals, since these are generated later by
2356 @code{NoteHead} layout objects rather than by music elements in the
2359 Such indirectly created layout objects can be tweaked using the form
2360 of the @code{\tweak} command in which the grob name is specified
2363 @lilypond[relative=2,verbatim,quote]
2364 \tweak Stem.color #red
2365 \tweak Beam.color #green c8 e
2366 <c e \tweak Accidental.font-size #-3 ges>4
2369 @code{\tweak} cannot be used to modify clefs or time
2370 signatures, since these become separated from any preceding
2371 @code{\tweak} command in the input stream by the automatic
2372 insertion of extra elements required to specify the context.
2374 Several @code{\tweak} commands may be placed before a
2375 notational element -- all affect it:
2377 @lilypond[verbatim,quote,relative=1]
2379 -\tweak style #'dashed-line
2380 -\tweak dash-fraction #0.2
2381 -\tweak thickness #3
2387 The music stream which is generated from a section of an input file,
2388 including any automatically inserted elements, may be examined,
2389 see @rextend{Displaying music expressions}. This may be helpful in
2390 determining what may be modified by a @code{\tweak} command, or
2391 in determining how to adjust the input to make a @code{\tweak}
2396 @rlearning{Tweaking methods}.
2399 @rextend{Displaying music expressions}.
2403 @cindex tweaking control points
2404 @cindex control points, tweaking
2406 The @code{\tweak} command cannot be used to modify the control
2407 points of just one of several ties in a chord, other than the first
2408 one encountered in the input file.
2410 @node set versus override
2411 @subsection @code{\set} vs. @code{\override}
2413 @c TODO Should't a bunch of that be explained earlier?
2417 Both @code{\set} and @code{\override} manipulate properties
2418 associated with contexts. In either case, properties heed the
2419 hierarchy of contexts: properties not set in a context itself show
2420 the values of the respective parent context.
2422 Values and lifetime of context properties are dynamic and only
2423 available when music is being interpreted, @q{iterated}. At the
2424 time of context creation, properties are initialized from the
2425 corresponding context definition and possible context
2426 modifications. Afterwards, changes are achieved with
2427 property-setting commands in the music itself.
2429 Now grob definitions are a special category of context properties.
2430 Since their structure, bookkeeping and use is different from
2431 ordinary context properties, they are accessed with a different
2432 set of commands, and treated separately in the documentation.
2434 As opposed to plain context properties, grob definitions are
2435 subdivided into grob properties. A @qq{grob} (graphical object)
2436 is usually created by an engraver at the time of interpreting a
2437 music expression and receives its initial properties from the
2438 current grob definition of the engraver's context. The engraver
2439 (or other @q{backend} parts of LilyPond) may subsequently add or
2440 change properties to the grob, but that does not affect the
2441 context's grob definition.
2443 What we call @q{grob properties} in the context of user-level
2444 tweaking are actually the properties of a context's grob
2445 definition. In contrast to ordinary context properties, grob
2446 definitions have the bookkeeping required to keep track of its
2447 parts, the individual grob properties (and even subproperties of
2448 them) separately so that it is possible to define those parts in
2449 different contexts and have the overall grob definition at the
2450 time of grob creation be assembled from pieces provided in
2451 different contexts among the current context and its parents.
2453 Grob definitions are manipulated using @code{\override} and
2454 @code{\revert} and have a name starting with a capital letter
2455 (like @samp{NoteHead}) whereas ordinary context properties are
2456 manipulated using @code{\set} and @code{\unset} and are named
2457 starting with a lowercase letter.
2459 @cindex tweak, relation to @code{\override}
2461 @funindex \overrideProperty
2462 The special commands @code{\tweak} and @code{\overrideProperty}
2463 change grob properties bypassing context properties completely.
2464 Instead they catch grobs as they are being created and then
2465 directly set properties on them when they originate from a tweaked
2466 music event or are of a particular kind, respectively.
2468 @node Modifying alists
2469 @subsection Modifying alists
2471 Some user-configurable properties are internally represented as
2472 @emph{alists} (association lists), which store pairs of
2473 @emph{keys} and @emph{values}. The structure of an alist is:
2476 '((@var{key1} . @var{value1})
2477 (@var{key2} . @var{value2})
2478 (@var{key3} . @var{value3})
2482 If an alist is a grob property or @code{\paper} variable, its keys
2483 can be modified individually without affecting other keys.
2485 For example, to reduce the space between adjacent staves in a
2486 staff-group, use the @code{staff-staff-spacing} property of the
2487 @code{StaffGrouper} grob. The property is an alist with four
2488 keys: @code{basic-distance}, @code{minimum-distance},
2489 @code{padding}, and @code{stretchability}. The standard settings
2490 for this property are listed in the @qq{Backend} section of the
2491 Internals Reference (see @rinternals{StaffGrouper}):
2494 '((basic-distance . 9)
2495 (minimum-distance . 7)
2497 (stretchability . 5))
2500 One way to bring the staves closer together is by reducing the
2501 value of the @code{basic-distance} key (@code{9}) to match the
2502 value of @code{minimum-distance} (@code{7}). To modify a single
2503 key individually, use a @emph{nested declaration}:
2505 @lilypond[quote,verbatim]
2506 % default space between staves
2508 \new Staff { \clef treble c''1 }
2509 \new Staff { \clef bass c1 }
2512 % reduced space between staves
2513 \new PianoStaff \with {
2514 % this is the nested declaration
2515 \override StaffGrouper.staff-staff-spacing.basic-distance = #7
2517 \new Staff { \clef treble c''1 }
2518 \new Staff { \clef bass c1 }
2522 Using a nested declaration will update the specified key (such as
2523 @code{basic-distance} in the above example) without altering any
2524 other keys already set for the same property.
2526 Now suppose we want the staves to be as close as possible without
2527 overlapping. The simplest way to do this is to set all four alist
2528 keys to zero. However, it is not necessary to enter four nested
2529 declarations, one for each key. Instead, the property can be
2530 completely re-defined with one declaration, as an alist:
2532 @lilypond[quote,verbatim]
2533 \new PianoStaff \with {
2534 \override StaffGrouper.staff-staff-spacing =
2535 #'((basic-distance . 0)
2536 (minimum-distance . 0)
2538 (stretchability . 0))
2540 \new Staff { \clef treble c''1 }
2541 \new Staff { \clef bass c1 }
2545 Note that any keys not explicitly listed in the alist definition
2546 will be reset to their @emph{default-when-unset} values. In the
2547 case of @code{staff-staff-spacing}, any unset key-values would be
2548 reset to zero (except @code{stretchability}, which takes the value
2549 of @code{basic-distance} when unset). Thus the following two
2550 declarations are equivalent:
2553 \override StaffGrouper.staff-staff-spacing =
2554 #'((basic-distance . 7))
2556 \override StaffGrouper.staff-staff-spacing =
2557 #'((basic-distance . 7)
2558 (minimum-distance . 0)
2560 (stretchability . 7))
2563 One (possibly unintended) consequence of this is the removal of
2564 any standard settings that are set in an initialization file and
2565 loaded each time an input file is compiled. In the above example,
2566 the standard settings for @code{padding} and
2567 @code{minimum-distance} (defined in @file{scm/define-grobs.scm})
2568 are reset to their default-when-unset values (zero for both keys).
2569 Defining a property or variable as an alist (of any size) will
2570 always reset all unset key-values to their default-when-unset
2571 values. Unless this is the intended result, it is safer to update
2572 key-values individually with a nested declaration.
2574 @warning{Nested declarations will not work for context property
2575 alists (such as @code{beamExceptions}, @code{keyAlterations},
2576 @code{timeSignatureSettings}, etc.). These properties can only be
2577 modified by completely re-defining them as alists.}
2580 @node Useful concepts and properties
2581 @section Useful concepts and properties
2586 * Direction and placement::
2587 * Distances and measurements::
2588 * Staff symbol properties::
2590 * Visibility of objects::
2592 * Rotating objects::
2596 @subsection Input modes
2598 The way in which the notation contained within an input file is
2599 interpreted is determined by the current input mode.
2601 @subsubsubheading Chord mode
2603 This is activated with the @code{\chordmode} command, and causes
2604 input to be interpreted with the syntax of chord notation, see
2605 @ref{Chord notation}. Chords are rendered as notes on a staff.
2607 Chord mode is also activated with the @code{\chords} command.
2608 This also creates a new @code{ChordNames} context and
2609 causes the following input to be interpreted with the syntax of
2610 chord notation and rendered as chord names in the @code{ChordNames}
2611 context, see @ref{Printing chord names}.
2613 @subsubsubheading Drum mode
2615 This is activated with the @code{\drummode} command, and causes
2616 input to be interpreted with the syntax of drum notation, see
2617 @ref{Basic percussion notation}.
2619 Drum mode is also activated with the @code{\drums} command.
2620 This also creates a new @code{DrumStaff} context and causes the
2621 following input to be interpreted with the syntax of drum notation
2622 and rendered as drum symbols on a drum staff, see
2623 @ref{Basic percussion notation}.
2625 @subsubsubheading Figure mode
2627 This is activated with the @code{\figuremode} command, and causes
2628 input to be interpreted with the syntax of figured bass, see
2629 @ref{Entering figured bass}.
2631 Figure mode is also activated with the @code{\figures} command.
2632 This also creates a new @code{FiguredBass} context and causes the
2633 following input to be interpreted with the figured bass syntax
2634 and rendered as figured bass symbols in the @code{FiguredBass}
2635 context, see @ref{Introduction to figured bass}.
2637 @subsubsubheading Fret and tab modes
2639 There are no special input modes for entering fret and tab symbols.
2641 To create tab diagrams, enter notes or chords in note mode and
2642 render them in a @code{TabStaff} context, see
2643 @ref{Default tablatures}.
2645 To create fret diagrams above a staff, you have two choices.
2646 You can either use the @code{FretBoards} context (see
2647 @ref{Automatic fret diagrams} or you can enter them as a markup
2648 above the notes using the @code{\fret-diagram} command (see
2649 @ref{Fret diagram markups}).
2651 @subsubsubheading Lyrics mode
2653 This is activated with the @code{\lyricmode} command, and causes
2654 input to be interpreted as lyric syllables with optional durations
2655 and associated lyric modifiers, see @ref{Vocal music}.
2657 Lyric mode is also activated with the @code{\addlyrics} command.
2658 This also creates a new @code{Lyrics} context and an implicit
2659 @code{\lyricsto} command which associates the following lyrics
2660 with the preceding music.
2662 @subsubsubheading Markup mode
2664 This is activated with the @code{\markup} command, and causes
2665 input to be interpreted with the syntax of markup, see
2666 @ref{Text markup commands}.
2668 @subsubsubheading Note mode
2670 This is the default mode or it may be activated with the
2671 @code{\notemode} command. Input is interpreted as pitches,
2672 durations, markup, etc and typeset as musical notation on a staff.
2674 It is not normally necessary to specify note mode explicitly, but
2675 it may be useful to do so in certain situations, for example if you
2676 are in lyric mode, chord mode or any other mode and want to insert
2677 something that only can be done with note mode syntax.
2680 @node Direction and placement
2681 @subsection Direction and placement
2683 In typesetting music the direction and placement of many items is
2684 a matter of choice. For example, the stems of notes can
2685 be directed up or down; lyrics, dynamics, and other expressive
2686 marks may be placed above or below the staff; text may be aligned
2687 left, right or center; etc. Most of these choices may be left to
2688 be determined automatically by LilyPond, but in some cases it may
2689 be desirable to force a particular direction or placement.
2692 * Articulation direction indicators::
2693 * The direction property::
2696 @node Articulation direction indicators
2697 @unnumberedsubsubsec Articulation direction indicators
2699 By default some directions are always up or always down (e.g.
2700 dynamics or fermata), while other things can alternate between
2701 up or down based on the stem direction (like slurs or accents).
2703 @c TODO Add table showing these
2705 The default action may be overridden by prefixing the articulation
2706 by a @emph{direction indicator}. Three direction indicators are
2707 available: @code{^} (meaning @qq{up}), @code{_} (meaning @qq{down})
2708 and @code{-} (meaning @qq{use default direction}). The direction
2709 indicator can usually be omitted, in which case @code{-} is assumed,
2710 but a direction indicator is @strong{always} required before
2713 @item @code{\tweak} commands
2714 @item @code{\markup} commands
2715 @item @code{\tag} commands
2716 @item string markups, e.g. -"string"
2717 @item fingering instructions, e.g. @w{@code{-1}}
2718 @item articulation shortcuts, e.g. @w{@code{-.}}, @w{@code{->}}, @w{@code{--}}
2721 Direction indicators affect only the next note:
2723 @lilypond[verbatim,quote,relative=2]
2730 @node The direction property
2731 @unnumberedsubsubsec The direction property
2733 The position or direction of many layout objects is controlled by the
2734 @code{direction} property.
2736 The value of the @code{direction} property may be set to @code{1},
2737 meaning @qq{up} or @qq{above}, or to @w{@code{-1}}, meaning @qq{down} or
2738 @qq{below}. The symbols @code{UP} and @code{DOWN} may be used instead
2739 of @code{1} and @w{@code{-1}} respectively. The default direction may
2740 be specified by setting @code{direction} to @code{0} or @code{CENTER}.
2741 Alternatively, in many cases predefined commands exist to specify the
2742 direction. These are of the form
2745 @code{\xxxUp}, @code{\xxxDown} or @code{\xxxNeutral}
2749 where @code{\xxxNeutral} means @qq{use the default} direction.
2750 See @rlearning{Within-staff objects}.
2752 In a few cases, arpeggio for example, the value of the @code{direction}
2753 property can specify whether the object is to be placed to the right or
2754 left of the parent. In this case @w{@code{-1}} or @code{LEFT} means
2755 @qq{to the left} and @code{1} or @code{RIGHT} means @qq{to the right}.
2756 @code{0} or @code{CENTER} means @qq{use the default} direction.
2759 These all have side-axis set to #X
2760 AmbitusAccidental - direction has no effect
2762 StanzaNumber - not tried
2763 TrillPitchAccidental - not tried
2764 TrillPitchGroup - not tried
2767 These indications affect all notes until they are canceled.
2769 @lilypond[verbatim,quote,relative=2]
2778 In polyphonic music, it is generally better to specify an explicit
2779 @code{voice} than change an object's direction. For more information.
2780 See @ref{Multiple voices}.
2784 @rlearning{Within-staff objects}.
2787 @ref{Multiple voices}.
2790 @node Distances and measurements
2791 @subsection Distances and measurements
2793 @cindex distances, absolute
2794 @cindex distances, scaled
2801 Distances in LilyPond are of two types: absolute and scaled.
2803 Absolute distances are used for specifying margins, indents, and
2804 other page layout details, and are by default specified in
2805 millimeters. Distances may be specified in other units by
2806 following the quantity by @code{\mm}, @code{\cm},
2807 @code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27 of
2808 an inch). Page layout distances can also be specified in scalable
2809 units (see the following paragraph) by appending
2810 @code{\staff-space} to the quantity. Page layout is described in
2811 detail in @ref{Page layout}.
2813 Scaled distances are always specified in units of the staff-space
2814 or, rarely, the half staff-space. The staff-space is the distance
2815 between two adjacent staff lines. The default value can be changed
2816 globally by setting the global staff size, or it can be overridden
2817 locally by changing the @code{staff-space} property of
2818 @code{StaffSymbol}. Scaled distances automatically scale with any
2819 change to the either the global staff size or the
2820 @code{staff-space} property of @code{StaffSymbol}, but fonts scale
2821 automatically only with changes to the global staff size.
2822 The global staff size thus enables the overall size of a rendered
2823 score to be easily varied. For the methods of setting the global
2824 staff size see @ref{Setting the staff size}.
2828 If just a section of a score needs to be rendered to a different
2829 scale, for example an ossia section or a footnote, the global staff
2830 size cannot simply be changed as this would affect the entire score.
2831 In such cases the change in size is made by overriding both the
2832 @code{staff-space} property of @code{StaffSymbol} and the size of
2833 the fonts. A Scheme function, @code{magstep}, is available to
2834 convert from a font size change to the equivalent change in
2835 @code{staff-space}. For an explanation and an example of its use,
2836 see @rlearning{Length and thickness of objects}.
2840 @rlearning{Length and thickness of objects}.
2844 @ref{Setting the staff size}.
2847 @node Staff symbol properties
2848 @subsection Staff symbol properties
2850 @cindex adjusting staff symbol
2851 @cindex drawing staff symbol
2852 @cindex staff symbol, setting of
2854 @c TODO Extend or remove this section. See also NR 1.6.2 Staff symbol
2855 @c Need to think of uses for these properties. Eg 'line-positions
2856 @c is used in a snippet to thicken centre line.
2857 @c If retained, add @ref to here in 1.6.2 -td
2859 The vertical position of staff lines and the number of staff lines
2860 can be defined at the same time. As the following example shows,
2861 note positions are not influenced by the staff line positions.
2863 @warning{The @code{'line-positions} property overrides the
2864 @code{'line-count} property. The number of staff lines is
2865 implicitly defined by the number of elements in the list of values
2866 for @code{'line-positions}.}
2868 @lilypond[verbatim,quote,relative=1]
2870 \override StaffSymbol.line-positions = #'(7 3 0 -4 -6 -7)
2875 The width of a staff can be modified. The units are staff
2876 spaces. The spacing of objects inside the staff is not affected by
2879 @lilypond[verbatim,quote,relative=1]
2881 \override StaffSymbol.width = #23
2888 @subsection Spanners
2890 Many objects of musical notation extend over several notes or even
2891 several bars. Examples are slurs, beams, tuplet brackets, volta
2892 repeat brackets, crescendi, trills, and glissandi. Such objects
2893 are collectively called @qq{spanners}, and have special properties to control
2894 their appearance and behaviour. Some of these properties are common
2895 to all spanners; others are restricted to a sub-set of the spanners.
2897 All spanners support the @code{spanner-interface}. A few, essentially
2898 those that draw a straight line between the two objects, support in
2899 addition the @code{line-spanner-interface}.
2902 * Using the spanner-interface::
2903 * Using the line-spanner-interface::
2906 @node Using the spanner-interface
2907 @unnumberedsubsubsec Using the @code{spanner-interface}
2909 This interface provides two properties that apply to several spanners.
2911 @subsubsubheading The @code{minimum-length} property
2913 The minimum length of the spanner is specified by the
2914 @code{minimum-length} property. Increasing this usually has the
2915 necessary effect of increasing the spacing of the notes between the
2916 two end points. However, this override has no effect on
2917 many spanners, as their length is determined by other considerations.
2918 A few examples where it is effective are shown below.
2928 Works as long as callback is made:
2932 Works not at all for:
2941 @lilypond[verbatim,quote,relative=2]
2944 % increase the length of the tie
2945 -\tweak minimum-length #5
2949 @lilypond[verbatim,quote,relative=2]
2951 \compressFullBarRests
2953 % increase the length of the rest bar
2954 \once \override MultiMeasureRest.minimum-length = #20
2959 @lilypond[verbatim,quote,relative=2]
2961 % increase the length of the hairpin
2962 \override Hairpin.minimum-length = #20
2966 This override can also be used to increase the length of slurs and
2969 @lilypond[verbatim,quote,relative=2]
2972 -\tweak minimum-length #5
2977 -\tweak minimum-length #5
2981 For some layout objects, the @code{minimum-length} property becomes
2982 effective only if the @code{set-spacing-rods} procedure is called
2983 explicitly. To do this, the @code{springs-and-rods} property should
2984 be set to @code{ly:spanner::set-spacing-rods}. For example,
2985 the minimum length of a glissando has no effect unless the
2986 @code{springs-and-rods} property is set:
2988 @lilypond[verbatim,quote,relative=1]
2992 % not effective alone
2993 \once \override Glissando.minimum-length = #20
2996 % effective only when both overrides are present
2997 \once \override Glissando.minimum-length = #20
2998 \once \override Glissando.springs-and-rods = #ly:spanner::set-spacing-rods
3002 The same is true of the @code{Beam} object:
3004 @lilypond[verbatim,quote,relative=1]
3005 % not effective alone
3006 \once \override Beam.minimum-length = #20
3009 % effective only when both overrides are present
3010 \once \override Beam.minimum-length = #20
3011 \once \override Beam.springs-and-rods = #ly:spanner::set-spacing-rods
3015 @subsubsubheading The @code{to-barline} property
3017 The second useful property of the @code{spanner-interface} is
3018 @code{to-barline}. By default this is true, causing hairpins and
3019 other spanners which are terminated on the first note of a measure to
3020 end instead on the immediately preceding bar line. If set to false,
3021 the spanner will extend beyond the bar line and end on the note
3024 @lilypond[verbatim,quote,relative=2]
3025 a \< a a a a \! a a a \break
3026 \override Hairpin.to-barline = ##f
3027 a \< a a a a \! a a a
3030 This property is not effective for all spanners. For example,
3031 setting it to @code{#t} has no effect on slurs or phrasing slurs
3032 or on other spanners for which terminating on the bar line would
3035 @node Using the line-spanner-interface
3036 @unnumberedsubsubsec Using the @code{line-spanner-interface}
3038 Objects which support the @code{line-spanner-interface} include
3041 @item @code{DynamicTextSpanner}
3042 @item @code{Glissando}
3043 @item @code{TextSpanner}
3044 @item @code{TrillSpanner}
3045 @item @code{VoiceFollower}
3048 The routine responsible for drawing the stencils for these spanners is
3049 @code{ly:line-interface::print}. This routine determines the
3050 exact location of the two end points and draws a line
3051 between them, in the style requested. The locations of the two
3052 end points of the spanner are computed on-the-fly, but it is
3053 possible to override their Y-coordinates. The
3054 properties which need to be specified are nested
3055 two levels down within the property hierarchy, but the syntax of
3056 the @code{\override} command is quite simple:
3058 @lilypond[relative=2,quote,verbatim]
3060 \once \override Glissando.bound-details.left.Y = #3
3061 \once \override Glissando.bound-details.right.Y = #-2
3065 The units for the @code{Y} property are @code{staff-space}s,
3066 with the center line of the staff being the zero point.
3067 For the glissando, this is the value for @code{Y} at the
3068 X-coordinate corresponding to the center point of each note head,
3069 if the line is imagined to be extended to there.
3071 If @code{Y} is not set, the value is computed from the vertical
3072 position of the corresponding attachment point of the spanner.
3074 In case of a line break, the values for the end points are
3075 specified by the @code{left-broken} and @code{right-broken}
3076 sub-lists of @code{bound-details}. For example:
3078 @lilypond[relative=2,ragged-right,verbatim,quote]
3079 \override Glissando.breakable = ##t
3080 \override Glissando.bound-details.right-broken.Y = #-3
3081 c1 \glissando \break
3086 A number of further properties of the @code{left} and
3087 @code{right} sub-lists of the @code{bound-details} property
3088 may be modified in the same way as @code{Y}:
3092 This sets the Y-coordinate of the end point, in @code{staff-space}s
3093 offset from the staff center line. By default, it is the center of
3094 the bound object, so a glissando points to the vertical center of
3097 For horizontal spanners, such as text spanners and trill spanners,
3098 it is hardcoded to 0.
3101 This determines where the line starts and ends in the X-direction,
3102 relative to the bound object. So, a value of @w{@code{-1}} (or
3103 @code{LEFT}) makes the line start/end at the left side of the note
3104 head it is attached to.
3107 This is the absolute X-coordinate of the end point. It is usually
3108 computed on the fly, and overriding it has little useful effect.
3111 Line spanners may have symbols at the beginning or end, which is
3112 contained in this sub-property. This is for internal use; it is
3113 recommended that @code{text} be used instead.
3116 This is a markup that is evaluated to yield the stencil. It is used
3117 to put @i{cresc.}, @i{tr} and other text on horizontal spanners.
3119 @lilypond[quote,ragged-right,relative=2,verbatim]
3120 \override TextSpanner.bound-details.left.text
3121 = \markup { \small \bold Slower }
3122 c2\startTextSpan b c a\stopTextSpan
3125 @item stencil-align-dir-y
3126 @item stencil-offset
3127 Without setting one of these, the stencil is simply put at the
3128 end-point, centered on the line, as defined by the @code{X} and
3129 @code{Y} sub-properties. Setting either @code{stencil-align-dir-y}
3130 or @code{stencil-offset} will move the symbol at the edge vertically
3131 relative to the end point of the line:
3133 @lilypond[relative=1,quote,verbatim]
3134 \override TextSpanner.bound-details.left.stencil-align-dir-y = #-2
3135 \override TextSpanner.bound-details.right.stencil-align-dir-y = #UP
3137 \override TextSpanner.bound-details.left.text = #"ggg"
3138 \override TextSpanner.bound-details.right.text = #"hhh"
3139 c4^\startTextSpan c c c \stopTextSpan
3142 Note that negative values move the text @emph{up}, contrary to the
3143 effect that might be expected, as a value of @w{@code{-1}} or
3144 @code{DOWN} means align the @emph{bottom} edge of the text with
3145 the spanner line. A value of @code{1} or @code{UP} aligns
3146 the top edge of the text with the spanner line.
3149 Setting this sub-property to @code{#t} produces an arrowhead at the
3153 This sub-property controls the space between the specified
3154 end point of the line and the actual end. Without padding, a
3155 glissando would start and end in the center of each note head.
3159 The music function @code{\endSpanners} terminates the spanner
3160 which starts on the immediately following note prematurely. It
3161 is terminated after exactly one note, or at the following bar line
3162 if @code{to-barline} is true and a bar line occurs before the next
3165 @lilypond[verbatim,quote,ragged-right,relative=2]
3167 c2 \startTextSpan c2 c2
3172 When using @code{\endSpanners} it is not necessary to close
3173 \startTextSpan with \stopTextSpan, nor is it necessary to close
3174 hairpins with @code{\!}.
3177 Internals Reference:
3178 @rinternals{TextSpanner},
3179 @rinternals{Glissando},
3180 @rinternals{VoiceFollower},
3181 @rinternals{TrillSpanner},
3182 @rinternals{line-spanner-interface}.
3185 @node Visibility of objects
3186 @subsection Visibility of objects
3188 @cindex objects, visibility of
3189 @cindex grobs, visibility of
3190 @cindex visibility of objects
3192 There are four main ways in which the visibility of layout objects
3193 can be controlled: their stencil can be removed, they can be made
3194 transparent, they can be colored white, or their
3195 @code{break-visibility} property can be overridden. The first
3196 three apply to all layout objects; the last to just a few -- the
3197 @emph{breakable} objects. The Learning Manual introduces these
3198 four techniques, see @rlearning{Visibility and color of objects}.
3200 There are also a few other techniques which are specific to
3201 certain layout objects. These are covered under Special
3205 * Removing the stencil::
3206 * Making objects transparent::
3207 * Painting objects white::
3208 * Using break-visibility::
3209 * Special considerations::
3213 @node Removing the stencil
3214 @unnumberedsubsubsec Removing the stencil
3216 @cindex stencil, removing
3219 Every layout object has a stencil property. By default this is set
3220 to the specific function which draws that object. If this property
3221 is overridden to @code{#f} no function will be called and the object
3222 will not be drawn. The default action can be recovered with
3225 @lilypond[quote,verbatim,relative=1]
3227 \override Score.BarLine.stencil = ##f
3229 \revert Score.BarLine.stencil
3233 This rather common operation has a shortcut @code{\omit}:
3235 @lilypond[quote,verbatim,relative=1]
3239 \undo \omit Score.BarLine
3243 @node Making objects transparent
3244 @unnumberedsubsubsec Making objects transparent
3246 @cindex transparent, making objects
3249 Every layout object has a transparent property which by default is
3250 set to @code{#f}. If set to @code{#t} the object still occupies
3251 space but is made invisible.
3253 @lilypond[quote,verbatim,relative=2]
3255 \once \override NoteHead.transparent = ##t
3259 This rather common operation has a shortcut @code{\hide}:
3261 @lilypond[quote,verbatim,relative=2]
3263 \once \hide NoteHead
3267 @node Painting objects white
3268 @unnumberedsubsubsec Painting objects white
3270 @cindex objects, coloring
3271 @cindex coloring objects
3273 @cindex printing order
3274 @cindex overwriting objects
3275 @cindex objects, overwriting
3276 @cindex grobs, overwriting
3278 Every layout object has a color property which by default is set
3279 to @code{black}. If this is overridden to @code{white} the object
3280 will be indistinguishable from the white background. However,
3281 if the object crosses other objects the color of the crossing
3282 points will be determined by the order in which they are drawn,
3283 and this may leave a ghostly image of the white object, as shown
3286 @lilypond[quote,verbatim,relative=2]
3287 \override Staff.Clef.color = #white
3291 This may be avoided by changing the order of printing the objects.
3292 All layout objects have a @code{layer} property which should be set
3293 to an integer. Objects with the lowest value of @code{layer} are
3294 drawn first, then objects with progressively higher values are drawn,
3295 so objects with higher values overwrite objects with lower values.
3296 By default most objects are assigned a @code{layer} value of
3297 @code{1}, although a few objects, including @code{StaffSymbol} and
3298 @code{BarLine}, are assigned a value of @code{0}. The order of
3299 printing objects with the same value of @code{layer} is indeterminate.
3301 In the example above the white clef, with a default @code{layer}
3302 value of @code{1}, is drawn after the staff lines (default
3303 @code{layer} value @code{0}), so overwriting them. To change this,
3304 the @code{Clef} object must be given in a lower value of
3305 @code{layer}, say @w{@code{-1}}, so that it is drawn earlier:
3307 @lilypond[quote,verbatim,relative=2]
3308 \override Staff.Clef.color = #white
3309 \override Staff.Clef.layer = #-1
3313 @node Using break-visibility
3314 @unnumberedsubsubsec Using break-visibility
3316 @c TODO Add making other objects breakable
3318 @cindex break-visibility
3320 Most layout objects are printed only once, but some like
3321 bar lines, clefs, time signatures and key signatures, may need
3322 to be printed twice when a line break occurs -- once at the end
3323 of the line and again at the start of the next line. Such
3324 objects are called @emph{breakable}, and have a property, the
3325 @code{break-visibility} property to control their visibility
3326 at the three positions in which they may appear -- at the
3327 start of a line, within a line if they are changed, and at the
3328 end of a line if a change takes place there.
3330 For example, the time signature
3331 by default will be printed at the start of the first line, but
3332 nowhere else unless it changes, when it will be printed at the
3333 point at which the change occurs. If this change occurs at the
3334 end of a line the new time signature will be printed at the start
3335 of the next line and a cautionary time signature will be printed
3336 at the end of the previous line as well.
3338 This behaviour is controlled by the @code{break-visibility}
3339 property, which is explained in
3340 @c Leave this ref on a newline - formats incorrectly otherwise -td
3341 @rlearning{Visibility and color of objects}. This property takes
3342 a vector of three booleans which, in order, determine whether the
3343 object is printed at the end of, within the body of, or at the
3344 beginning of a line. Or to be more precise, before a line break,
3345 where there is no line break, or after a line break.
3347 Alternatively, these eight combinations may be specified
3348 by pre-defined functions, defined in @file{scm/output-lib.scm},
3349 where the last three columns indicate whether the layout objects
3350 will be visible in the positions shown at the head of the columns:
3352 @multitable {@code{begin-of-line-invisible}} {@code{'#(#t #t #t)}} {Before} {At no} {After}
3353 @headitem Function @tab Vector @tab Before @tab At no @tab After
3354 @headitem form @tab form @tab break @tab break @tab break
3356 @item @code{all-visible} @tab @code{'#(#t #t #t)} @tab yes @tab yes @tab yes
3357 @item @code{begin-of-line-visible} @tab @code{'#(#f #f #t)} @tab no @tab no @tab yes
3358 @item @code{center-visible} @tab @code{'#(#f #t #f)} @tab no @tab yes @tab no
3359 @item @code{end-of-line-visible} @tab @code{'#(#t #f #f)} @tab yes @tab no @tab no
3360 @item @code{begin-of-line-invisible} @tab @code{'#(#t #t #f)} @tab yes @tab yes @tab no
3361 @item @code{center-invisible} @tab @code{'#(#t #f #t)} @tab yes @tab no @tab yes
3362 @item @code{end-of-line-invisible} @tab @code{'#(#f #t #t)} @tab no @tab yes @tab yes
3363 @item @code{all-invisible} @tab @code{'#(#f #f #f)} @tab no @tab no @tab no
3366 The default settings of @code{break-visibility} depend on the
3367 layout object. The following table shows all the layout objects
3368 of interest which are affected by @code{break-visibility} and the
3369 default setting of this property:
3371 @multitable @columnfractions .3 .3 .4
3373 @headitem Layout object @tab Usual context @tab Default setting
3375 @c omit Ambitus as it appears not to be affected by break-visibility -td
3376 @c @item @code{Ambitus} @tab as specified @tab @code{begin-of-line-visible}
3377 @item @code{BarLine} @tab @code{Score} @tab calculated
3378 @item @code{BarNumber} @tab @code{Score} @tab @code{begin-of-line-visible}
3379 @c omit the following item until it can be explained -td
3380 @c @item @code{BreakAlignGroup} @tab @code{Score} @tab calculated
3381 @item @code{BreathingSign} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3382 @item @code{Clef} @tab @code{Staff} @tab @code{begin-of-line-visible}
3383 @item @code{Custos} @tab @code{Staff} @tab @code{end-of-line-visible}
3384 @item @code{DoublePercentRepeat} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3385 @item @code{KeyCancellation} @tab @code{Staff} @tab @code{begin-of-line-invisible}
3386 @item @code{KeySignature} @tab @code{Staff} @tab @code{begin-of-line-visible}
3387 @c omit LeftEdge until it can be explained -td
3388 @c @item @code{LeftEdge} @tab @code{Score} @tab @code{center-invisible}
3389 @item @code{ClefModifier} @tab @code{Staff} @tab @code{begin-of-line-visible}
3390 @item @code{RehearsalMark} @tab @code{Score} @tab @code{end-of-line-invisible}
3391 @item @code{TimeSignature} @tab @code{Staff} @tab @code{all-visible}
3395 The example below shows the use of the vector form to control the
3396 visibility of bar lines:
3398 @lilypond[quote,verbatim,relative=1,ragged-right]
3401 % Remove bar line at the end of the current line
3402 \once \override Score.BarLine.break-visibility = ##(#f #t #t)
3408 Although all three components of the vector used to override
3409 @code{break-visibility} must be present, not all of them are
3410 effective with every layout object, and some combinations may
3411 even give errors. The following limitations apply:
3414 @item Bar lines cannot be printed at start of line.
3415 @item A bar number cannot be printed at the start of the first
3416 line unless it is set to be different from 1.
3417 @item Clef -- see below
3418 @item Double percent repeats are either all printed or all
3419 suppressed. Use begin-of line-invisible to print and
3420 all-invisible to suppress.
3421 @item Key signature -- see below
3422 @item ClefModifier -- see below
3425 @node Special considerations
3426 @unnumberedsubsubsec Special considerations
3428 @subsubsubheading Visibility following explicit changes
3430 @cindex key signature, visibility following explicit change
3431 @cindex explicitKeySignatureVisibility
3432 @cindex clef, visibility following explicit change
3433 @cindex explicitClefVisibility
3435 The @code{break-visibility} property controls the visibility of
3436 key signatures and changes of clef only at the start of lines,
3437 i.e. after a break. It has no effect on the visibility of the
3438 key signature or clef following an explicit key change or an
3439 explicit clef change within or at the end of a line. In the
3440 following example the key signature following the explicit change
3441 to B-flat major is still visible, even though @code{all-invisible}
3444 @lilypond[quote,verbatim,relative=1,ragged-right]
3447 % Try to remove all key signatures
3448 \override Staff.KeySignature.break-visibility = #all-invisible
3456 The visibility of such explicit key signature and clef changes is
3457 controlled by the @code{explicitKeySignatureVisibility} and
3458 @code{explicitClefVisibility} properties. These are the equivalent
3459 of the @code{break-visibility} property and both take a vector of
3460 three booleans or the predefined functions listed above, exactly like
3461 @code{break-visibility}. Both are properties of the Staff context,
3462 not the layout objects themselves, and so they are set using the
3463 @code{\set} command. Both are set by default to @code{all-visible}.
3464 These properties control only the visibility of key signatures and
3465 clefs resulting from explicit changes and do not affect key
3466 signatures and clefs at the beginning of lines;
3467 @code{break-visibility} must still be overridden in the appropriate
3468 object to remove these.
3470 @lilypond[quote,verbatim,relative=1,ragged-right]
3473 \set Staff.explicitKeySignatureVisibility = #all-invisible
3474 \override Staff.KeySignature.break-visibility = #all-invisible
3481 @subsubsubheading Visibility of cancelling accidentals
3483 To remove the cancelling accidentals printed at an explicit key
3484 change, set the Staff context property @code{printKeyCancellation}
3487 @lilypond[quote,verbatim,relative=1,ragged-right]
3490 \set Staff.explicitKeySignatureVisibility = #all-invisible
3491 \set Staff.printKeyCancellation = ##f
3492 \override Staff.KeySignature.break-visibility = #all-invisible
3499 With these overrides only the accidentals before the notes remain
3500 to indicate the change of key.
3502 Note that when changing the key to C@tie{}major or A@tie{}minor
3503 the cancelling accidentals would be the @emph{only} indication of
3504 the key change. In this case setting @code{printKeyCancellation} to
3505 @code{#f} has no effect:
3507 @lilypond[quote,verbatim,relative=1,ragged-right]
3510 \set Staff.explicitKeySignatureVisibility = #all-invisible
3511 \set Staff.printKeyCancellation = ##f
3518 To suppress the cancelling accidentals even when the key is
3519 changed to C@tie{}major or A@tie{}minor, override
3520 the visibility of the @code{KeyCancellation} grob instead:
3522 @lilypond[quote,verbatim,relative=1,ragged-right]
3525 \set Staff.explicitKeySignatureVisibility = #all-invisible
3526 \override Staff.KeyCancellation.break-visibility = #all-invisible
3533 @c TODO Add visibility of cautionary accidentals before notes
3535 @subsubsubheading Automatic bars
3537 @cindex automaticBars
3538 @cindex bar lines, suppressing
3540 As a special case, the printing of bar lines can also be turned off
3541 by setting the @code{automaticBars} property in the Score context.
3542 If set to @code{#f}, bar lines will not be printed automatically;
3543 they must be explicitly created with a @code{\bar} command. Unlike
3544 the @code{\cadenzaOn} predefined command, measures are still counted.
3545 Bar generation will resume according to that count if this property
3546 is later set to @code{#t}. When set to @code{#f}, line breaks can
3547 occur only at explicit @code{\bar} commands.
3551 @subsubsubheading Transposed clefs
3553 @cindex transposed clefs, visibility of
3554 @cindex visibility of transposed clefs
3555 @cindex clefs, visibility of transposition
3557 The small transposition symbol on transposed clefs is produced by the
3558 @code{ClefModifier} layout object. Its visibility is automatically
3559 inherited from the @code{Clef} object, so it is not necessary to apply
3560 any required @code{break-visibility} overrides to the @code{ClefModifier}
3561 layout objects to suppress transposition symbols for invisible clefs.
3563 For explicit clef changes, the @code{explicitClefVisibility}
3564 property controls both the clef symbol and any transposition symbol
3569 @rlearning{Visibility and color of objects}.
3573 @subsection Line styles
3575 Some performance indications, e.g., @i{rallentando} and
3576 @i{accelerando} and @i{trills} are written as text and are
3577 extended over many measures with lines, sometimes dotted or wavy.
3579 These all use the same routines as the glissando for drawing the
3580 texts and the lines, and tuning their behavior is therefore also
3581 done in the same way. It is done with a spanner, and the routine
3582 responsible for drawing the spanners is
3583 @code{ly:line-interface::print}. This routine determines the
3584 exact location of the two @i{span points} and draws a line
3585 between them, in the style requested.
3587 Here is an example showing the different line styles available,
3588 and how to tune them.
3590 @lilypond[relative=2,ragged-right,verbatim,quote]
3592 \once \override Glissando.style = #'dashed-line
3594 \override Glissando.style = #'dotted-line
3596 \override Glissando.style = #'zigzag
3598 \override Glissando.style = #'trill
3602 The locations of the end-points of the spanner are computed
3603 on-the-fly for every graphic object, but it is possible to
3607 @lilypond[relative=2,ragged-right,verbatim,quote]
3609 \once \override Glissando.bound-details.right.Y = #-2
3613 The value for @code{Y} is set to @w{@code{-2}} for the right end
3614 point. The left side may be similarly adjusted by specifying
3615 @code{left} instead of @code{right}.
3617 If @code{Y} is not set, the value is computed from the vertical
3618 position of the left and right attachment points of the spanner.
3620 Other adjustments of spanners are possible, for details, see
3623 @node Rotating objects
3624 @subsection Rotating objects
3626 Both layout objects and elements of markup text can be rotated by
3627 any angle about any point, but the method of doing so differs.
3630 * Rotating layout objects::
3634 @node Rotating layout objects
3635 @unnumberedsubsubsec Rotating layout objects
3637 @cindex rotating objects
3638 @cindex objects, rotating
3640 All layout objects which support the @code{grob-interface} can be
3641 rotated by setting their @code{rotation} property. This takes a
3642 list of three items: the angle of rotation counter-clockwise,
3643 and the x and y coordinates of the point relative to the object's
3644 reference point about which the rotation is to be performed. The
3645 angle of rotation is specified in degrees and the coordinates in
3648 The angle of rotation and the coordinates of the rotation point must
3649 be determined by trial and error.
3651 @cindex hairpins, angled
3652 @cindex angled hairpins
3654 There are only a few situations where the rotation of layout
3655 objects is useful; the following example shows one situation where
3658 @lilypond[quote,verbatim,relative=1]
3660 \override Hairpin.rotation = #'(20 -1 0)
3664 @node Rotating markup
3665 @unnumberedsubsubsec Rotating markup
3667 All markup text can be rotated to lie at any angle by prefixing it
3668 with the @code{\rotate} command. The command takes two arguments:
3669 the angle of rotation in degrees counter-clockwise and the text to
3670 be rotated. The extents of the text are not rotated: they take
3671 their values from the extremes of the x and y coordinates of the
3672 rotated text. In the following example the
3673 @code{outside-staff-priority} property for text is set to @code{#f}
3674 to disable the automatic collision avoidance, which would push some
3675 of the text too high.
3677 @lilypond[quote,verbatim,relative=1]
3678 \override TextScript.outside-staff-priority = ##f
3679 g4^\markup { \rotate #30 "a G" }
3680 b^\markup { \rotate #30 "a B" }
3681 des^\markup { \rotate #30 "a D-Flat" }
3682 fis^\markup { \rotate #30 "an F-Sharp" }
3685 @node Advanced tweaks
3686 @section Advanced tweaks
3688 This section discusses various approaches to fine tuning the
3689 appearance of the printed score.
3692 * Aligning objects::
3693 * Vertical grouping of grobs::
3694 * Modifying stencils::
3695 * Modifying shapes::
3696 * Modifying broken spanners::
3697 * Unpure-pure containers::
3702 @rlearning{Tweaking output},
3703 @rlearning{Other sources of information}.
3706 @ref{Explaining the Internals Reference},
3707 @ref{Modifying properties}.
3710 @rextend{Interfaces for programmers}.
3713 @file{scm/define-grobs.scm}.
3716 @rlsr{Tweaks and overrides}.
3718 Internals Reference:
3719 @rinternals{All layout objects}.
3722 @node Aligning objects
3723 @subsection Aligning objects
3725 Graphical objects which support the @code{self-alignment-interface}
3726 and/or the @code{side-position-interface} can be aligned to a previously
3727 placed object in a variety of ways. For a list of these objects, see
3728 @rinternals{self-alignment-interface} and @rinternals{side-position-interface}.
3730 All graphical objects have a reference point, a horizontal extent and a
3731 vertical extent. The horizontal extent is a pair of numbers
3732 giving the displacements from the reference point of the left and
3733 right edges, displacements to the left being negative. The vertical
3734 extent is a pair of numbers giving the displacement from the reference
3735 point to the bottom and top edges, displacements down being negative.
3737 An object's position on a staff is given by the values of the
3738 @code{X-offset} and @code{Y-offset} properties. The value of
3739 @code{X-offset} gives the displacement from the X coordinate of
3740 the reference point of the parent object, and the value of
3741 @code{Y-offset} gives the displacement from the center line of the
3742 staff. The values of @code{X-offset} and @code{Y-offset} may
3743 be set directly or may be set to be calculated by procedures in order
3744 to achieve alignment with the parent object.
3746 @warning{Many objects have special positioning considerations which
3747 cause any setting of @code{X-offset} or @code{Y-offset} to be
3748 ignored or modified, even though the object supports the
3749 @code{self-alignment-interface}. Overriding the @code{X-offset}
3750 or @code{Y-offset} properties to a fixed value causes the respective
3751 @code{self-alignment} property to be disregarded.}
3753 For example, an accidental can be repositioned vertically by setting
3754 @code{Y-offset} but any changes to @code{X-offset} have no effect.
3756 Rehearsal marks may be aligned with breakable objects such as bar
3757 lines, clef symbols, time signature symbols and key signatures. There
3758 are special properties to be found in the @code{break-aligned-interface}
3759 for positioning rehearsal marks on such objects.
3763 @ref{Using the break-alignable-interface}.
3766 @rextend{Callback functions}.
3769 * Setting X-offset and Y-offset directly::
3770 * Using the side-position-interface::
3771 * Using the self-alignment-interface::
3772 * Using the break-alignable-interface::
3775 @node Setting X-offset and Y-offset directly
3776 @unnumberedsubsubsec Setting @code{X-offset} and @code{Y-offset} directly
3778 Numerical values may be given to the @code{X-offset} and @code{Y-offset}
3779 properties of many objects. The following example shows three
3780 notes with the default fingering position and the positions with @code{X-offset}
3781 and @code{Y-offset} modified.
3783 @lilypond[verbatim,quote,relative=2]
3790 -\tweak X-offset #-1
3797 @node Using the side-position-interface
3798 @unnumberedsubsubsec Using the @code{side-position-interface}
3800 An object which supports the @code{side-position-interface} can be
3801 placed next to its parent object so that
3802 the specified edges of the two objects touch. The object may be
3803 placed above, below, to the right or to the left of the parent.
3804 The parent cannot be specified; it is determined by the order of
3805 elements in the input stream. Most objects have the associated
3806 note head as their parent.
3808 The values of the @code{side-axis} and @code{direction} properties
3809 determine where the object is to be placed, as follows:
3811 @c TODO add an example of each to the table
3813 @multitable @columnfractions .3 .3 .3
3814 @headitem @code{side-axis} @tab @code{direction} @tab
3815 @headitem property @tab property @tab Placement
3817 @item @code{0} @tab @code{-1} @tab left
3818 @item @code{0} @tab @code{1} @tab right
3819 @item @code{1} @tab @code{-1} @tab below
3820 @item @code{1} @tab @code{1} @tab above
3824 When @code{side-axis} is @code{0}, @code{X-offset} should be set to
3825 the procedure @code{ly:side-position-interface::x-aligned-side}.
3826 This procedure will return the correct value of @code{X-offset} to
3827 place the object to the left or right side of the parent according
3828 to value of @code{direction}.
3830 When @code{side-axis} is @code{1}, @code{Y-offset} should be set to
3831 the procedure @code{ly:side-position-interface::y-aligned-side}.
3832 This procedure will return the correct value of @code{Y-offset} to
3833 place the object to the top or bottom of the parent according
3834 to value of @code{direction}.
3836 @c TODO Add examples
3838 @node Using the self-alignment-interface
3839 @unnumberedsubsubsec Using the @code{self-alignment-interface}
3841 @subsubsubheading Self-aligning objects horizontally
3843 The horizontal alignment of an object which supports the
3844 @code{self-alignment-interface} is controlled by the value of
3845 the @code{self-alignment-X} property, provided the object's
3846 @code{X-offset} property is set to
3847 @code{ly:self-alignment-interface::x-aligned-on-self}.
3848 @code{self-alignment-X} may be given any
3849 real value, in units of half the total X extent of the
3850 object. Negative values move the object to the right, positive
3851 to the left. A value of @code{0} centers the object on the
3852 reference point of its parent, a value of @w{@code{-1}} aligns the
3853 left edge of the object on the reference point of its parent,
3854 and a value of @code{1} aligns the right edge of the object on the
3855 reference point of its parent. The symbols @code{LEFT},
3856 @code{CENTER}, and @code{RIGHT} may be used instead of the values
3857 @w{@code{-1}}, @code{0}, and @code{1}, respectively.
3859 Normally the @code{\override} command would be used to modify the
3860 value of @code{self-alignment-X}, but the @code{\tweak} command
3861 can be used to separately align several annotations on a single
3864 @lilypond[quote,verbatim,relative=1]
3866 -\tweak self-alignment-X #-1
3868 -\tweak self-alignment-X #0
3870 -\tweak self-alignment-X #RIGHT
3872 -\tweak self-alignment-X #-2.5
3873 ^"aligned further to the right"
3876 @subsubsubheading Self-aligning objects vertically
3878 Objects may be aligned vertically in an analogous way to aligning
3879 them horizontally if the @code{Y-offset} property is set to
3880 @code{ly:self-alignment-interface::y-aligned-on-self}. However,
3881 other mechanisms are often involved in vertical alignment: the
3882 value of @code{Y-offset} is just one variable taken into account.
3883 This may make adjusting the value of some objects tricky.
3884 The units are just half the vertical extent of the object, which
3885 is usually quite small, so quite large numbers may be required.
3886 A value of @w{@code{-1}} aligns the lower edge of the object with
3887 the reference point of the parent object, a value of @code{0}
3888 aligns the center of the object with the reference point of the
3889 parent, and a value of @code{1} aligns the top edge of the object
3890 with the reference point of the parent. The symbols @code{DOWN},
3891 @code{CENTER}, and @code{UP} may be substituted for @w{@code{-1}},
3892 @code{0}, and @code{1}, respectively.
3894 @subsubsubheading Self-aligning objects in both directions
3896 By setting both @code{X-offset} and @code{Y-offset}, an object may
3897 be aligned in both directions simultaneously.
3899 The following example shows how to adjust a fingering mark so
3900 that it nestles close to the note head.
3902 @lilypond[quote,verbatim,relative=2]
3904 -\tweak self-alignment-X #0.5 % move horizontally left
3905 -\tweak Y-offset #ly:self-alignment-interface::y-aligned-on-self
3906 -\tweak self-alignment-Y #-1 % move vertically up
3911 @unnumberedsubsubsec Using the @code{aligned-on-parent} procedures
3913 @c Cannot document as they do not seem to operate consistently on all objects -td
3914 @c TODO investigate further
3916 The @code{aligned-on-parent} procedures are used in the same way
3917 as the @code{aligned-on-self} procedures, they difference being
3918 that they permit an object to be aligned with the @emph{edges} of
3919 the parent rather than the parent's reference point. The following
3920 example shows the difference:
3924 @lilypond[verbatim,quote]
3930 @unnumberedsubsubsec Using the @code{centered-on-parent} procedures
3932 @c Cannot document as they do not seem to operate consistently on all objects -td
3933 @c TODO investigate further
3937 @c TODO The align-interface, BassFigureAlignment and VerticalAlignment
3939 @node Using the break-alignable-interface
3940 @unnumberedsubsubsec Using the @code{break-alignable-interface}
3942 @cindex align to objects
3943 @cindex break-align-symbols
3945 Rehearsal marks and bar numbers may be aligned with notation
3946 objects other than bar lines. These objects include @code{ambitus},
3947 @code{breathing-sign}, @code{clef}, @code{custos}, @code{staff-bar},
3948 @code{left-edge}, @code{key-cancellation}, @code{key-signature}, and
3949 @code{time-signature}.
3951 Each type of object has its own default reference point, to which
3952 rehearsal marks are aligned:
3954 @lilypond[verbatim,quote,relative=1]
3955 % The rehearsal mark will be aligned to the right edge of the Clef
3956 \override Score.RehearsalMark.break-align-symbols = #'(clef)
3961 % The rehearsal mark will be aligned to the left edge of the Time Signature
3962 \override Score.RehearsalMark.break-align-symbols = #'(time-signature)
3968 % The rehearsal mark will be centered above the Breath Mark
3969 \override Score.RehearsalMark.break-align-symbols = #'(breathing-sign)
3978 A list of possible target alignment objects may be specified. If
3979 some of the objects are invisible at that point due to the setting
3980 of @code{break-visibility} or the explicit visibility settings for
3981 keys and clefs, the rehearsal mark or bar number is aligned to the
3982 first object in the list which is visible. If no objects in the
3983 list are visible the object is aligned to the bar line. If the bar
3984 line is invisible the object is aligned to the place where the bar
3987 @lilypond[verbatim,quote,relative=1]
3988 % The rehearsal mark will be aligned to the right edge of the Key Signature
3989 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
3994 % The rehearsal mark will be aligned to the right edge of the Clef
3995 \set Staff.explicitKeySignatureVisibility = #all-invisible
3996 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4001 % The rehearsal mark will be centered above the Bar Line
4002 \set Staff.explicitKeySignatureVisibility = #all-invisible
4003 \set Staff.explicitClefVisibility = #all-invisible
4004 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4011 The alignment of the rehearsal mark relative to the notation object
4012 can be changed, as shown in the following example. In a score with
4013 multiple staves, this setting should be done for all the staves.
4015 @lilypond[verbatim,quote,relative=1]
4016 % The RehearsalMark will be aligned with the right edge of the Key Signature
4017 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4023 % The RehearsalMark will be centered above the Key Signature
4024 \once \override Score.KeySignature.break-align-anchor-alignment = #CENTER
4028 % The RehearsalMark will be aligned with the left edge of the Key Signature
4029 \once \override Score.KeySignature.break-align-anchor-alignment = #LEFT
4035 The rehearsal mark can also be offset to the right or left of the left
4036 edge by an arbitrary amount. The units are staff-spaces:
4038 @lilypond[verbatim,quote,relative=1]
4039 % The RehearsalMark will be aligned with the left edge of the Key Signature
4040 % and then shifted right by 3.5 staff-spaces
4041 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4042 \once \override Score.KeySignature.break-align-anchor = #3.5
4046 % The RehearsalMark will be aligned with the left edge of the Key Signature
4047 % and then shifted left by 2 staff-spaces
4048 \once \override Score.KeySignature.break-align-anchor = #-2
4055 @node Vertical grouping of grobs
4056 @subsection Vertical grouping of grobs
4058 @c TODO Expand this section
4060 The VerticalAlignment and VerticalAxisGroup grobs work together.
4061 VerticalAxisGroup groups together different grobs like Staff, Lyrics,
4062 etc. VerticalAlignment then vertically aligns the different grobs
4063 grouped together by VerticalAxisGroup. There is usually only one
4064 VerticalAlignment per score but every Staff, Lyrics, etc. has its own
4068 @node Modifying stencils
4069 @subsection Modifying stencils
4071 All layout objects have a @code{stencil} property which is part of
4072 the @code{grob-interface}. By default, this property is usually
4073 set to a function specific to the object that is tailor-made to
4074 render the symbol which represents it in the output. For example,
4075 the standard setting for the @code{stencil} property of the
4076 @code{MultiMeasureRest} object is @code{ly:multi-measure-rest::print}.
4078 The standard symbol for any object can be replaced by modifying the
4079 @code{stencil} property to reference a different, specially-written,
4080 procedure. This requires a high level of knowledge of the internal
4081 workings of LilyPond, but there is an easier way which can often
4082 produce adequate results.
4084 This is to set the @code{stencil} property to the procedure which
4085 prints text -- @code{ly:text-interface::print} -- and to add a
4086 @code{text} property to the object which is set to contain the
4087 markup text which produces the required symbol. Due to the
4088 flexibility of markup, much can be achieved -- see in particular
4089 @ref{Graphic notation inside markup}.
4091 The following example demonstrates this by changing the note head
4092 symbol to a cross within a circle.
4094 @lilypond[verbatim,quote]
4096 \once \override NoteHead.stencil = #ly:text-interface::print
4097 \once \override NoteHead.text = \markup {
4099 \halign #-0.7 \draw-circle #0.85 #0.2 ##f
4100 \musicglyph #"noteheads.s2cross"
4108 Any of the glyphs in the feta Font can be supplied to the
4109 @code{\musicglyph} markup command -- see @ref{The Feta font}.
4111 @c TODO Add inserting eps files or ref to later
4113 @c TODO Add inserting Postscript or ref to later
4117 @ref{Graphic notation inside markup},
4118 @ref{Formatting text},
4119 @ref{Text markup commands},
4120 @ref{The Feta font}.
4123 @node Modifying shapes
4124 @subsection Modifying shapes
4127 * Modifying ties and slurs::
4130 @node Modifying ties and slurs
4131 @unnumberedsubsubsec Modifying ties and slurs
4133 @cindex slurs, modifying
4134 @cindex ties, modifying
4135 @cindex Bézier curves, control points
4136 @cindex control points, Bézier curves
4138 @code{Tie}s, @code{Slur}s, @code{PhrasingSlur}s,
4139 @code{LaissezVibrerTie}s and @code{RepeatTie}s are all drawn as
4140 third-order Bézier curves. If the shape of the tie or slur which
4141 is calculated automatically is not optimum, the shape may be
4142 modified manually in two ways:
4146 by specifying the displacements to be made to the control points
4147 of the automatically calculated Bézier curve, or
4150 by explicitly specifying the positions of the four control points
4151 required to define the wanted curve.
4154 Both methods are explained below. The first method is more suitable
4155 if only slight adjustments to the curve are required; the second may
4156 be better for creating curves which are related to just a single
4159 @subsubsubheading Cubic Bézier curves
4161 Third-order or cubic Bézier curves are defined by four control
4162 points. The first and fourth control points are precisely the
4163 starting and ending points of the curve. The intermediate two
4164 control points define the shape. Animations showing how the curve
4165 is drawn can be found on the web, but the following description
4166 may be helpful. The curve starts from the first control point
4167 heading directly towards the second, gradually bending over to
4168 head towards the third and continuing to bend over to head towards
4169 the fourth, arriving there travelling directly from the third
4170 control point. The curve is entirely contained in the
4171 quadrilateral defined by the four control points. Translations,
4172 rotations and scaling of the control points all result in exactly
4173 the same operations on the curve.
4175 @subsubsubheading Specifying displacements from current control points
4177 @cindex shaping slurs and ties
4180 In this example the automatic placement of the tie is not optimum,
4181 and @code{\tieDown} would not help.
4183 @lilypond[verbatim,quote,relative=1]
4187 { r4 <g c,> <g c,> <g c,> }
4191 Adjusting the control points of the tie with @code{\shape} allows
4192 the collisions to be avoided.
4194 The syntax of @code{\shape} is
4197 [-]@code{\shape} @var{displacements} @var{item}
4200 This will reposition the control-points of @var{item} by the amounts
4201 given by @var{displacements}. The @var{displacements} argument is a
4202 list of number pairs or a list of such lists. Each element of a pair
4203 represents the displacement of one of the coordinates of a
4204 control-point. If @var{item} is a string, the result is
4205 @code{\once\override} for the specified grob type. If @var{item} is
4206 a music expression, the result is the same music expression with an
4207 appropriate tweak applied.
4209 In other words, the @code{\shape} function can act as either a
4210 @code{\once\override} command or a @code{\tweak} command depending
4211 on whether the @var{item} argument is a grob name, like @qq{Slur},
4212 or a music expression, like @qq{(}. The @var{displacements} argument
4213 specifies the displacements of the four control points as a list of
4214 four pairs of (dx . dy) values in units of staff-spaces (or a list
4215 of such lists if the curve has more than one segment).
4217 The leading hyphen is required if and only if the @code{\tweak} form
4220 So, using the same example as above and the @code{\once\override}
4221 form of @code{\shape}, this will raise the tie by half a staff-space:
4223 @lilypond[verbatim,quote,relative=1]
4226 \shape #'((0 . 0.5) (0 . 0.5) (0 . 0.5) (0 . 0.5)) Tie
4230 { r4 <g c,> <g c,> <g c,> }
4234 This positioning of the tie is better, but maybe it should be raised
4235 more in the center. The following example does this, this time using
4236 the alternative @code{\tweak} form:
4238 @lilypond[verbatim,quote,relative=1]
4241 e1-\shape #'((0 . 0.5) (0 . 1) (0 . 1) (0 . 0.5)) ~ e
4244 { r4 <g c,> <g c,> <g c,> }
4248 Changes to the horizontal positions of the control points may be made
4249 in the same way, and two different curves starting at the same
4250 musical moment may also be shaped:
4252 @lilypond[verbatim,quote,ragged-right,relative=2]
4254 \shape #'((0.7 . -0.4) (0.5 . -0.4) (0.3 . -0.3) (0 . -0.2)) Slur
4255 \shape #'((0 . 0) (0 . 0.5) (0 . 0.5) (0 . 0)) PhrasingSlur
4259 The @code{\shape} function can also displace the control points of
4260 curves which stretch across line breaks. Each piece of the broken
4261 curve can be given its own list of offsets. If changes to a
4262 particular segment are not needed, the empty list can serve as a
4263 placeholder. In this example the line break makes the single slur
4266 @lilypond[verbatim,quote,ragged-right,relative=1]
4272 Changing the shapes of the two halves of the slur makes it clearer
4273 that the slur continues over the line break:
4275 @lilypond[verbatim,quote,ragged-right,relative=1]
4276 % () may be used as a shorthand for ((0 . 0) (0 . 0) (0 . 0) (0 . 0))
4277 % if any of the segments does not need to be changed
4279 (( 0 . 0) (0 . 0) (0 . 0) (0 . 1))
4280 ((0.5 . 1.5) (1 . 0) (0 . 0) (0 . -1.5))
4287 If an S-shaped curve is required the control points must always be
4288 adjusted manually --- LilyPond will never select such shapes
4291 @lilypond[verbatim,quote,relative=2]
4292 c8( e b-> f d' a e-> g)
4293 \shape #'((0 . -1) (5.5 . -0.5) (-5.5 . -10.5) (0 . -5.5)) PhrasingSlur
4294 c8\( e b-> f d' a e-> g\)
4297 @subsubsubheading Specifying control points explicitly
4299 The coordinates of the Bézier control points are specified in units
4300 of staff-spaces. The X@tie{}coordinate is relative to the reference
4301 point of the note to which the tie or slur is attached, and the
4302 Y@tie{}coordinate is relative to the staff center line. The
4303 coordinates are specified as a list of four pairs of decimal numbers
4304 (reals). One approach is to estimate the coordinates of the two
4305 end points, and then guess the two intermediate points. The optimum
4306 values are then found by trial and error. Be aware that these values
4307 may need to be manually adjusted if any further changes are made to
4308 the music or the layout.
4310 One situation where specifying the control points explicitly is
4311 preferable to specifying displacements is when they need to be
4312 specified relative to a single note. Here is an example of this.
4313 It shows one way of indicating a slur extending into alternative
4314 sections of a volta repeat.
4316 @lilypond[verbatim,quote,relative=2]
4318 \repeat volta 3 { c4 d( e f }
4323 % create a slur and move it to a new position
4324 % the <> is just an empty chord to carry the slur termination
4325 -\tweak control-points #'((-2 . 3.8) (-1 . 3.9) (0 . 4) (1 . 3.4)) ( <> )
4330 % create a slur and move it to a new position
4331 -\tweak control-points #'((-2 . 3) (-1 . 3.1) (0 . 3.2) (1 . 2.4)) ( <> )
4338 It is not possible to modify shapes of ties or slurs by changing
4339 the @code{control-points} property if there are multiple ties or slurs
4340 at the same musical moment -- the @code{\tweak} command will also not
4341 work in this case. However, the @code{tie-configuration} property of
4342 @code{TieColumn} can be overridden to set start line and direction as
4346 Internals Reference:
4347 @rinternals{TieColumn}.
4350 @node Modifying broken spanners
4351 @subsection Modifying broken spanners
4354 * Using alterBroken::
4357 @node Using alterBroken
4358 @unnumberedsubsubsec Using @code{\alterBroken}
4360 @cindex spanners, modifying
4361 @cindex broken spanners, modifying
4362 @funindex \alterBroken
4364 When a spanner crosses a line break or breaks, each piece
4365 inherits the attributes of the original spanner. Thus, ordinary
4366 tweaking of a broken spanner applies the same modifications to
4367 each of its segments. In the example below, overriding
4368 @code{thickness} affects the slur on either side of the line
4371 @lilypond[verbatim,quote,ragged-right,relative=2]
4373 \once\override Slur.thickness = 10
4379 Independently modifying the appearance of individual pieces
4380 of a broken spanner is possible with the @code{\alterBroken}
4381 command. This command can produce either an @code{\override}
4382 or a @code{\tweak} of a spanner property.
4384 The syntax for @code{\alterBroken} is
4387 [-]@code{\alterBroken} @var{property} @var{values} @var{item}
4390 The argument @var{values} is a list of values, one for each
4391 broken piece. If @var{item} is a grob name like @code{Slur} or
4392 @code{Staff.PianoPedalBracket}, the result is an @code{\override}
4393 of the specified grob type. If @var{item} is a music expression
4394 such as @qq{(} or @qq{[} the result is the same music expression
4395 with an appropriate tweak applied.
4397 The leading hyphen must be used with the @code{\tweak} form. Do
4398 not add it when @code{\alterBroken} is used as an
4401 In its @code{\override} usage, @code{\alterBroken} may be
4402 prefaced by @code{\once} or @code{\temporary} and reverted by
4403 using @code{\revert} with @var{property}.
4405 The following code applies an independent @code{\override} to
4406 each of the slur segments in the previous example:
4408 @lilypond[verbatim,quote,ragged-right,relative=2]
4410 \alterBroken thickness #'(10 1) Slur
4416 The @code{\alterBroken} command may be used with any spanner
4417 object, including @code{Tie}, @code{PhrasingSlur}, @code{Beam}
4418 and @code{TextSpanner}. For example, an editor preparing a
4419 scholarly edition may wish to indicate the absence of part of a
4420 phrasing slur in a source by dashing only the segment which has
4421 been added. The following example illustrates how this can be
4422 done, in this case using the @code{\tweak} form of the command:
4424 @lilypond[verbatim,quote,ragged-right,relative=2]
4425 % The empty list is conveniently used below, because it is the
4426 % default setting of dash-definition, resulting in a solid curve.
4427 c2-\alterBroken dash-definition #'(() ((0 1.0 0.4 0.75))) \(e
4432 It is important to understand that @code{\alterBroken} will set
4433 each piece of a broken spanner to the corresponding value in
4434 @var{values}. When there are fewer values than pieces, any
4435 additional piece will be assigned the empty list. This may lead
4436 to undesired results if the layout property is not set to the
4437 empty list by default. In such cases, each segment should be
4438 assigned an appropriate value.
4441 Line breaks may occur in different places following changes in
4442 layout. Settings chosen for @code{\alterBroken} may be unsuitable
4443 for a spanner that is no longer broken or is split into more
4444 segments than before. Explicit use of @code{\break} can guard
4445 against this situation.
4447 The @code{\alterBroken} command is ineffective for spanner
4448 properties accessed before line-breaking such as
4453 @rextend{Difficult tweaks}.
4456 @node Unpure-pure containers
4457 @subsection Unpure-pure containers
4459 @cindex Scheme, pure containers
4460 @cindex Scheme, unpure containers
4461 @cindex pure containers, Scheme
4462 @cindex unpure containers, Scheme
4463 @cindex horizontal spacing, overriding
4465 Unpure-pure containers are useful for overriding @emph{Y-axis} spacing
4466 calculations - specifically @code{Y-offset} and @code{Y-extent} - with a
4467 Scheme function instead of a literal (i.e. a number or pair).
4469 For certain grobs, the @code{Y-extent} is based on the @code{stencil}
4470 property, overriding the stencil property of one of these will
4471 require an additional @code{Y-extent} override with an unpure-pure
4472 container. When a function overrides a @code{Y-offset} and/or
4473 @code{Y-extent} it is assumed that this will trigger line breaking
4474 calculations too early during compilation. So the function is not
4475 evaluated at all (usually returning a value of @samp{0} or
4476 @samp{'(0 . 0)}) which can result in collisions. A @q{pure} function
4477 will not affect properties, objects or grob suicides and therefore will
4478 always have its Y-axis-related evaluated correctly.
4480 Currently, there are about thirty functions that are already considered
4481 @q{pure} and Unpure-pure containers are a way to set functions not on
4482 this list as @q{pure}. The @q{pure} function is evaluated @emph{before}
4483 any line-breaking and so the horizontal spacing can be adjusted
4484 @q{in time}. The @q{unpure} function is then evaluated @emph{after}
4487 @warning{As it is difficult to always know which functions are on this
4488 list we recommend that any @q{pure} functions you create do not use
4489 @code{Beam} or @code{VerticalAlignment} grobs.}
4491 An unpure-pure container is constructed as follows;
4493 @code{(ly:make-unpure-pure-container f0 f1)}
4495 where @code{f0} is a function taking @var{n} arguments (@var{n >= 1})
4496 and the first argument must always be the grob. This is the function
4497 that gives the actual result. @var{f1} is the function being labeled
4498 as @q{pure} that takes @var{n + 2} arguments. Again, the first argument
4499 must always still be the grob but the second and third are @q{start}
4500 and @q{end} arguments.
4502 @var{start} and @var{end} are, for all intents and purposes, dummy
4503 values that only matter for @code{Spanners} (i.e @code{Hairpin} or
4504 @code{Beam}), that can return different height estimations based on a
4505 starting and ending column.
4507 The rest are the other arguments to the first function (which
4508 may be none if @var{n = 1}).
4510 The results of the second function are used as an approximation of the
4511 value needed which is then used by the first function to get the real
4512 value which is then used for fine-tuning much later during the spacing
4515 @lilypond[verbatim,quote,ragged-right]
4516 #(define (square-line-circle-space grob)
4517 (let* ((pitch (ly:event-property (ly:grob-property grob 'cause) 'pitch))
4518 (notename (ly:pitch-notename pitch)))
4519 (if (= 0 (modulo notename 2))
4520 (make-circle-stencil 0.5 0.0 #t)
4521 (make-filled-box-stencil '(0 . 1.0)
4524 squareLineCircleSpace = {
4525 \override NoteHead.stencil = #square-line-circle-space
4528 smartSquareLineCircleSpace = {
4529 \squareLineCircleSpace
4530 \override NoteHead.Y-extent =
4531 #(ly:make-unpure-pure-container
4532 ly:grob::stencil-height
4533 (lambda (grob start end) (ly:grob::stencil-height grob)))
4536 \new Voice \with { \remove "Stem_engraver" }
4538 \squareLineCircleSpace
4540 \smartSquareLineCircleSpace
4545 In the first measure, without the unpure-pure container, the spacing
4546 engine does not know the width of the note head and lets it collide with
4547 the accidentals. In the second measure, with unpure-pure containers,
4548 the spacing engine knows the width of the note heads and avoids the
4549 collision by lengthening the line accordingly.
4551 Usually for simple calculations nearly-identical functions for both the
4552 @q{unpure} and @q{pure} parts can be used, by only changing the number
4553 of arguments passed to, and the scope of, the function.
4555 @warning{If a function is labeled as @q{pure} and it turns out not to
4556 be, the results can be unexpected.}
4559 @node Using music functions
4560 @section Using music functions
4562 @c TODO -- add @seealso, etc. to these subsections
4564 Where tweaks need to be reused with different music expressions,
4565 it is often convenient to make the tweak part of a @emph{music
4566 function}. In this section, we discuss only @emph{substitution}
4567 functions, where the object is to substitute a variable into a
4568 piece of LilyPond input code. Other more complex functions are
4569 described in @rextend{Music functions}.
4572 * Substitution function syntax::
4573 * Substitution function examples::
4576 @node Substitution function syntax
4577 @subsection Substitution function syntax
4579 Making a function that substitutes a variable into LilyPond
4580 code is easy. The general form of these functions is
4584 #(define-music-function
4585 (parser location @var{arg1} @var{arg2} @dots{})
4586 (@var{type1?} @var{type2?} @dots{})
4588 @var{@dots{}music@dots{}}
4595 @multitable @columnfractions .33 .66
4596 @item @code{@var{argN}}
4597 @tab @var{n}th argument
4599 @item @code{@var{typeN?}}
4600 @tab a scheme @emph{type predicate} for which @code{@var{argN}}
4601 must return @code{#t}.
4603 @item @code{@var{@dots{}music@dots{}}}
4604 @tab normal LilyPond input, using @code{$} (in places where only
4605 Lilypond constructs are allowed) or @code{#} (to use it as a Scheme
4606 value or music function argument or music inside of music lists) to
4611 The @code{parser} and @code{location} arguments are mandatory, and
4612 are used in some advanced situations as described in the
4613 @q{Extending} manual (see @rextend{Music functions}). For
4614 substitution functions, just be sure to include them.
4616 The list of type predicates is also required. Some of the most
4617 common type predicates used in music functions are:
4621 cheap-list? @emph{(use instead of }@q{list?}@emph{ for faster processing)}
4633 For a list of available type predicates, see
4634 @ref{Predefined type predicates}. User-defined type predicates
4639 @ref{Predefined type predicates}.
4642 @rextend{Music functions}.
4645 @file{lily/music-scheme.cc},
4647 @file{scm/lily.scm}.
4650 @node Substitution function examples
4651 @subsection Substitution function examples
4653 This section introduces some substitution function examples.
4654 These are not intended to be exhaustive, but rather to demonstrate
4655 some of the possibilities of simple substitution functions.
4657 In the first example, a function is defined that simplifies
4658 setting the padding of a TextScript:
4660 @lilypond[quote,verbatim,ragged-right]
4662 #(define-music-function
4663 (parser location padding)
4666 \once \override TextScript.padding = #padding
4670 c4^"piu mosso" b a b
4672 c4^"piu mosso" b a b
4674 c4^"piu mosso" b a b
4678 In addition to numbers, we can use music expressions such
4679 as notes for arguments to music functions:
4681 @lilypond[quote,verbatim,ragged-right]
4683 #(define-music-function
4684 (parser location note)
4687 \tweak NoteHead.stencil #ly:text-interface::print
4688 \tweak NoteHead.text
4689 \markup \musicglyph #"custodes.mensural.u0"
4690 \tweak Stem.stencil ##f
4694 \relative c' { c4 d e f \custosNote g }
4697 Substitution functions with multiple arguments can be defined:
4699 @lilypond[quote,verbatim,ragged-right]
4701 #(define-music-function
4702 (parser location padding tempotext)
4705 \once \override Score.MetronomeMark.padding = #padding
4706 \tempo \markup { \bold #tempotext }
4710 \tempo \markup { "Low tempo" }
4712 \tempoPadded #4.0 "High tempo"
4717 @c TODO: add appropriate @@ref's here.