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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 signatures, 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{Engraver_group},
1322 @rinternals{Note_heads_engraver},
1323 @rinternals{Text_engraver},
1324 @rinternals{Rhythmic_column_engraver},
1325 @rinternals{Pitch_squash_engraver}.
1328 @node Context layout order
1329 @subsection Context layout order
1331 @cindex contexts, layout order
1335 Contexts are normally positioned in a system from top to bottom
1336 in the order in which they are encountered in the input file. When
1337 contexts are nested, the outer context will include inner nested
1338 contexts as specified in the input file, provided the inner contexts
1339 are included in the outer context's @qq{accepts} list. Nested
1340 contexts which are not included in the outer context's @qq{accepts}
1341 list will be repositioned below the outer context rather than nested
1344 The @qq{accepts} list of a context can be changed with the
1345 @code{\accepts} or @code{\denies} commands. @code{\accepts} adds a
1346 context to the @qq{accepts} list and @code{\denies} removes a context
1349 For example, a square-braced staff group is not usually found within a
1350 curved-braced staff with connecting staff bars, and a @code{GrandStaff}
1351 does not accept a @code{StaffGroup} inside it by default.
1353 @lilypond[verbatim,quote]
1360 \new Staff { \set Staff.instrumentName = bottom f'1 }
1365 However, by using the @code{\accepts} command, @code{StaffGroup} can be
1366 added to the @code{GrandStaff} context:
1368 @lilypond[verbatim,quote]
1375 \new Staff { \set Staff.instrumentName = bottom f'1 }
1380 \accepts "StaffGroup"
1386 @code{\denies} is mainly used when a new context is being based on
1387 another, but the required nesting differs. For example, the
1388 @code{VaticanaStaff} context is based on the @code{Staff} context, but
1389 with the @code{VaticanaVoice} context substituted for the @code{Voice}
1390 context in the @qq{accepts} list.
1392 @cindex contexts, implicit
1393 @cindex implicit contexts
1394 @funindex \defaultchild
1396 Note that a context will be silently created implicitly if a
1397 command is encountered when there is no suitable context available
1400 Within a context definition, the type of subcontext to be
1401 implicitly created is specified using @code{\defaultchild}. A
1402 number of music events require a @samp{Bottom} context: when such
1403 an event is encountered, subcontexts are created recursively until
1404 reaching a context with no @samp{defaultchild} setting.
1406 Implicit context creation can at times give rise to unexpected new
1407 staves or scores. Using @code{\new} to create contexts explicitly
1408 avoids those problems.
1410 @cindex alignAboveContext
1411 @cindex alignBelowContext
1412 @funindex alignAboveContext
1413 @funindex alignBelowContext
1415 Sometimes a context is required to exist for just a brief period, a
1416 good example being the staff context for an ossia. This is usually
1417 achieved by introducing the context definition at the appropriate
1418 place in parallel with corresponding section of the main music.
1419 By default, the temporary context will be placed below all the
1420 existing contexts. To reposition it above the context called
1421 @qq{main}, it should be defined like this:
1424 @code{\new Staff \with @{ alignAboveContext = #"main" @} }
1427 A similar situation arises when positioning a temporary lyrics
1428 context within a multi-staved layout such as a @code{ChoirStaff},
1429 for example, when adding a second verse to a repeated section.
1430 By default the temporary lyrics context will be placed beneath the
1431 lower staves. By defining the temporary lyrics context with
1432 @code{alignBelowContext} it can be positioned correctly beneath
1433 the (named) lyrics context containing the first verse.
1435 Examples showing this repositioning of temporary contexts can be
1436 found elsewhere --- see @rlearning{Nesting music expressions},
1437 @ref{Modifying single staves} and @ref{Techniques specific to lyrics}.
1441 @rlearning{Nesting music expressions}.
1444 @ref{Modifying single staves},
1445 @ref{Techniques specific to lyrics}.
1448 @rprogram{An extra staff appears}.
1451 @file{ly/engraver-init.ly}.
1454 @node Explaining the Internals Reference
1455 @section Explaining the Internals Reference
1458 * Navigating the program reference::
1459 * Layout interfaces::
1460 * Determining the grob property::
1461 * Naming conventions::
1464 @node Navigating the program reference
1465 @subsection Navigating the program reference
1467 @c TODO remove this (it's in the LM)
1468 @c Replace with more factual directions
1470 Suppose we want to move the fingering indication in the fragment
1473 @lilypond[quote,relative=2,verbatim]
1479 If you visit the documentation on fingering instructions (in
1480 @ref{Fingering instructions}), you will notice:
1485 Internals Reference: @rinternals{Fingering}.
1490 @c outdated info; probably will delete.
1492 This fragment points to two parts of the program reference: a page
1493 on @code{FingeringEvent} and one on @code{Fingering}.
1495 The page on @code{FingeringEvent} describes the properties of the music
1496 expression for the input @w{@code{-2}}. The page contains many links
1497 forward. For example, it says
1500 Accepted by: @rinternals{Fingering_engraver},
1504 That link brings us to the documentation for the Engraver, the
1508 This engraver creates the following layout objects: @rinternals{Fingering}.
1511 In other words, once the @code{FingeringEvent}s are interpreted, the
1512 @code{Fingering_engraver} plug-in will process them.
1516 @c I can't figure out what this is supposed to mean. -gp
1518 The @code{Fingering_engraver} is also listed to create
1519 @rinternals{Fingering} objects,
1521 @c old info? it doesn't make any sense to me with our current docs.
1523 second bit of information listed under @b{See also} in the Notation
1528 The programmer's reference is available as an HTML document. It is
1529 highly recommended that you read it in HTML form, either online or
1530 by downloading the HTML documentation. This section will be much more
1531 difficult to understand if you are using the
1535 Follow the link to @rinternals{Fingering}. At the top of the
1539 Fingering objects are created by: @rinternals{Fingering_engraver} and
1540 @rinternals{New_fingering_engraver}.
1543 By following related links inside the program reference, we can follow the
1544 flow of information within the program:
1548 @item @rinternals{Fingering}:
1549 @rinternals{Fingering} objects are created by:
1550 @rinternals{Fingering_engraver}
1552 @item @rinternals{Fingering_engraver}:
1553 Music types accepted: @rinternals{fingering-event}
1555 @item @rinternals{fingering-event}:
1556 Music event type @code{fingering-event} is in Music expressions named
1557 @rinternals{FingeringEvent}
1560 This path goes against the flow of information in the program: it
1561 starts from the output, and ends at the input event. You could
1562 also start at an input event, and read with the flow of
1563 information, eventually ending up at the output object(s).
1565 The program reference can also be browsed like a normal document. It
1566 contains chapters on
1568 @rinternals{Music definitions},
1571 @code{Music definitions}
1573 on @rinternals{Translation}, and the @rinternals{Backend}. Every
1574 chapter lists all the definitions used and all properties that may be
1578 @node Layout interfaces
1579 @subsection Layout interfaces
1581 @cindex interface, layout
1582 @cindex layout interface
1585 The HTML page that we found in the previous section describes the
1586 layout object called @rinternals{Fingering}. Such an object is a
1587 symbol within the score. It has properties that store numbers (like
1588 thicknesses and directions), but also pointers to related objects. A
1589 layout object is also called a @emph{Grob}, which is short for Graphical
1590 Object. For more details about Grobs, see @rinternals{grob-interface}.
1592 The page for @code{Fingering} lists the definitions for the
1593 @code{Fingering} object. For example, the page says
1596 @code{padding} (dimension, in staff space):
1602 which means that the number will be kept at a distance of at least 0.5
1606 Each layout object may have several functions as a notational or
1607 typographical element. For example, the Fingering object
1608 has the following aspects
1612 Its size is independent of the horizontal spacing, unlike slurs or beams.
1615 It is a piece of text. Granted, it is usually a very short text.
1618 That piece of text is typeset with a font, unlike slurs or beams.
1621 Horizontally, the center of the symbol should be aligned to the
1622 center of the note head.
1625 Vertically, the symbol is placed next to the note and the staff.
1628 The vertical position is also coordinated with other superscript
1629 and subscript symbols.
1632 Each of these aspects is captured in so-called @emph{interface}s,
1633 which are listed on the @rinternals{Fingering} page at the bottom
1636 This object supports the following interfaces:
1637 @rinternals{item-interface},
1638 @rinternals{self-alignment-interface},
1639 @rinternals{side-position-interface}, @rinternals{text-interface},
1640 @rinternals{text-script-interface}, @rinternals{font-interface},
1641 @rinternals{finger-interface}, and @rinternals{grob-interface}.
1644 Clicking any of the links will take you to the page of the respective
1645 object interface. Each interface has a number of properties. Some of
1646 them are not user-serviceable (@q{Internal properties}), but others
1649 We have been talking of @emph{the} @code{Fingering} object, but actually it
1650 does not amount to much. The initialization file (see
1651 @rlearning{Other sources of information})
1652 @file{scm/define-grobs.scm} shows the soul of the @q{object},
1657 (avoid-slur . around)
1658 (slur-padding . 0.2)
1659 (staff-padding . 0.5)
1660 (self-alignment-X . 0)
1661 (self-alignment-Y . 0)
1662 (script-priority . 100)
1663 (stencil . ,ly:text-interface::print)
1664 (direction . ,ly:script-interface::calc-direction)
1665 (font-encoding . fetaText)
1666 (font-size . -5) ; don't overlap when next to heads.
1667 (meta . ((class . Item)
1668 (interfaces . (finger-interface
1670 text-script-interface
1672 side-position-interface
1673 self-alignment-interface
1674 item-interface))))))
1678 As you can see, the @code{Fingering} object is nothing more than a
1679 bunch of variable settings, and the webpage in the Internals Reference
1680 is directly generated from this definition.
1683 @node Determining the grob property
1684 @subsection Determining the grob property
1686 @c TODO remove this (it's in the LM)
1687 @c Replace with more factual directions
1689 Recall that we wanted to change the position of the @b{2} in
1691 @lilypond[quote,relative=2,verbatim]
1697 Since the @b{2} is vertically positioned next to its note, we have to
1698 meddle with the interface associated with this positioning. This is
1699 done using @code{side-position-interface}. The page for this interface
1703 @code{side-position-interface}
1705 Position a victim object (this one) next to other objects (the
1706 support). The property @code{direction} signifies where to put the
1707 victim object relative to the support (left or right, up or down?)
1712 Below this description, the variable @code{padding} is described as
1717 (dimension, in staff space)
1719 Add this much extra space between objects that are next to each other.
1723 By increasing the value of @code{padding}, we can move the
1724 fingering away from the note head. The following command inserts
1725 3 staff spaces of white
1726 between the note and the fingering:
1728 \once \override Voice.Fingering.padding = #3
1731 Inserting this command before the Fingering object is created,
1732 i.e., before @code{c2}, yields the following result:
1734 @lilypond[quote,relative=2,verbatim]
1735 \once \override Voice.Fingering.padding = #3
1742 In this case, the context for this tweak is @code{Voice}. This
1743 fact can also be deduced from the program reference, for the page for
1744 the @rinternals{Fingering_engraver} plug-in says
1747 Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
1751 @node Naming conventions
1752 @subsection Naming conventions
1754 Another thing that is needed, is an overview of the various naming
1758 @item scheme functions: lowercase-with-hyphens (incl. one-word
1760 @item scheme functions: ly:plus-scheme-style
1761 @item music events, music classes and music properties:
1763 @item Grob interfaces: scheme-style
1764 @item backend properties: scheme-style (but X and Y!)
1765 @item contexts (and MusicExpressions and grobs): Capitalized or
1767 @item context properties: lowercaseFollowedByCamelCase
1769 Capitalized_followed_by_lowercase_and_with_underscores
1772 Questions to be answered:
1774 @item Which of these are conventions and which are rules?
1775 @item Which are rules of the underlying language, and which are
1779 @node Modifying properties
1780 @section Modifying properties
1782 @c TODO change the menu and subsection node names to use
1783 @c backslash once the new macro to handle the refs
1784 @c is available. Need to find and change all refs at
1785 @c the same time. -td
1788 * Overview of modifying properties::
1790 * The override command::
1791 * The tweak command::
1792 * set versus override::
1793 * Modifying alists::
1797 @node Overview of modifying properties
1798 @subsection Overview of modifying properties
1800 Each context is responsible for creating certain types of graphical
1801 objects. The settings used for printing these objects are also stored by
1802 context. By changing these settings, the appearance of objects can be
1805 There are two different kinds of properties stored in contexts:
1806 context properties and grob properties. Context properties are
1807 properties that apply to the context as a whole and control
1808 how the context itself is displayed. In contrast, grob properties
1809 apply to specific grob types that will be displayed in the context.
1811 The @code{\set} and @code{\unset} commands are used to change values
1812 for context properties. The @code{\override} and @code{\revert}
1813 commands are used to change values for grob properties.
1816 The syntax for this is
1819 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1822 Here @var{name} is the name of a graphical object, like
1823 @code{Stem} or @code{NoteHead}, and @var{property} is an internal
1824 variable of the formatting system (@q{grob property} or @q{layout
1825 property}). The latter is a symbol, so it must be quoted. The
1826 subsection @ref{Modifying properties}, explains what to fill in
1827 for @var{name}, @var{property}, and @var{value}. Here we only
1828 discuss the functionality of this command.
1833 \override Staff.Stem.thickness = #4.0
1837 makes stems thicker (the default is 1.3, with staff line thickness as a
1838 unit). Since the command specifies @code{Staff} as context, it only
1839 applies to the current staff. Other staves will keep their normal
1840 appearance. Here we see the command in action:
1842 @lilypond[quote,verbatim,relative=2]
1844 \override Staff.Stem.thickness = #4.0
1850 The @code{\override} command changes the definition of the @code{Stem}
1851 within the current @code{Staff}. After the command is interpreted
1852 all stems are thickened.
1854 Analogous to @code{\set}, the @var{context} argument may be left out,
1855 causing the default context @code{Voice} to be used. Adding
1856 @code{\once} applies the change during one timestep only.
1858 @lilypond[quote,verbatim,relative=2]
1860 \once \override Stem.thickness = #4.0
1865 The @code{\override} must be done before the object is
1866 started. Therefore, when altering @emph{Spanner} objects such as slurs
1867 or beams, the @code{\override} command must be executed at the moment
1868 when the object is created. In this example,
1870 @lilypond[quote,verbatim,relative=2]
1871 \override Slur.thickness = #3.0
1873 \override Beam.beam-thickness = #0.6
1878 the slur is fatter but the beam is not. This is because the command for
1879 @code{Beam} comes after the Beam is started, so it has no effect.
1881 Analogous to @code{\unset}, the @code{\revert} command for a context
1882 undoes an @code{\override} command; like with @code{\unset}, it only
1883 affects settings that were made in the same context. In other words, the
1884 @code{\revert} in the next example does not do anything.
1887 \override Voice.Stem.thickness = #4.0
1888 \revert Staff.Stem.thickness
1891 Some tweakable options are called @q{subproperties} and reside inside
1892 properties. To tweak those, use commands of the form
1894 @c leave this as a long long
1896 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
1903 \override Stem.details.beamed-lengths = #'(4 4 3)
1909 Internals Reference:
1910 @rinternals{Backend},
1911 @rinternals{All layout objects},
1912 @rinternals{OverrideProperty},
1913 @rinternals{RevertProperty},
1914 @rinternals{PropertySet}.
1917 The back-end is not very strict in type-checking object properties.
1918 Cyclic references in Scheme values for properties can cause hangs
1919 or crashes, or both.
1922 @node The set command
1923 @subsection The @code{@bs{}set} command
1927 @cindex changing properties
1929 Each context has a set of @emph{properties}, variables contained
1930 in that context. Context properties are changed with the @code{\set}
1931 command, which has the following syntax:
1934 \set @var{context}.@var{property} = #@var{value}
1937 @var{value} is a Scheme object, which is why it must be preceded by
1938 the @code{#}@tie{}character.
1940 Contexts properties are usually named in
1941 @code{studlyCaps}. They mostly control the translation from
1942 music to notation, e.g. @code{localAlterations} (for determining
1943 whether to print accidentals), or @code{measurePosition} (for
1944 determining when to print a bar line). Context properties can
1945 change value over time while interpreting a piece of music;
1946 @code{measurePosition} is an obvious example of
1947 this. Context properties are modified with @code{\set}.
1949 For example, multimeasure rests will be combined into a single bar
1950 if the context property @code{skipBars} is set to @code{#t}:
1952 @lilypond[quote,verbatim,relative=2]
1954 \set Score.skipBars = ##t
1958 If the @var{context} argument is left out, then the property will be
1959 set in the current bottom context (typically @code{ChordNames},
1960 @code{Voice}, @code{TabVoice}, or @code{Lyrics}).
1962 @lilypond[quote,verbatim,relative=2]
1963 \set Score.autoBeaming = ##f
1967 \set autoBeaming = ##t
1975 The change is applied @q{on-the-fly}, during the music, so that the
1976 setting only affects the second group of eighth notes.
1978 Note that the bottom-most context does not always contain the property
1979 that you wish to change -- for example, attempting to set the
1980 @code{skipBars} property of the default bottom context, in this case
1981 @code{Voice}, will have no effect, because skipBars is a property of
1982 the @code{Score} context.
1984 @lilypond[quote,verbatim,relative=2]
1990 Contexts are hierarchical, so if an enclosing context was specified, for
1991 example @code{Staff}, then the change would also apply to all
1992 @code{Voice}s in the current staff.
1996 The @code{\unset} command:
1999 \unset @var{context}.@var{property}
2003 is used to remove the definition of @var{property} from
2004 @var{context}. This command removes
2005 the definition only if it is set in @var{context}.
2006 Properties that have been set in enclosing contexts will
2007 not be altered by an unset in an enclosed context:
2009 @lilypond[quote,verbatim,relative=2]
2010 \set Score.autoBeaming = ##t
2015 \unset Score.autoBeaming
2023 Like @code{\set}, the @var{context} argument does not have to be
2024 specified for a bottom context, so the two statements
2027 \set Voice.autoBeaming = ##t
2028 \set autoBeaming = ##t
2032 are equivalent if the current bottom context is @code{Voice}.
2036 Preceding a @code{\set} command by @code{\once} makes the
2037 setting apply to only a single time-step:
2039 @lilypond[quote,verbatim,relative=2]
2041 \once \set fontSize = #4.7
2046 A full description of all available context properties is in the
2047 internals reference, see
2049 @rinternals{Tunable context properties}.
2052 Translation @expansion{} Tunable context properties.
2056 Internals Reference:
2057 @rinternals{Tunable context properties}.
2060 @node The override command
2061 @subsection The @code{\override} command
2063 @cindex grob properties
2064 @cindex properties, grob
2067 There is a special type of context property: the grob
2068 description. Grob descriptions are named in @code{StudlyCaps}
2069 (starting with capital letters). They contain the
2070 @q{default settings} for a particular kind of grob as an
2071 association list. See @file{scm/define-grobs.scm}
2072 to see the settings for each grob description. Grob descriptions
2073 are modified with @code{\override}.
2075 The syntax for the @code{\override} command is
2078 \override [@var{context}.]@var{GrobName}.@var{property} = #@var{value}
2081 For example, we can increase the thickness of a note stem by
2082 overriding the @code{thickness} property of the @code{Stem}
2085 @lilypond[quote,verbatim,relative=2]
2087 \override Voice.Stem.thickness = #3.0
2091 If no context is specified in an @code{\override}, the bottom
2094 @lilypond[quote,verbatim,relative=2]
2095 { \override Staff.Stem.thickness = #3.0
2099 \override Stem.thickness = #0.5
2108 Some tweakable options are called @q{subproperties} and reside inside
2109 properties. To tweak those, use commands in the form
2112 \override Stem.details.beamed-lengths = #'(4 4 3)
2115 or to modify the ends of spanners, use a form like these
2118 \override TextSpanner.bound-details.left.text = #"left text"
2119 \override TextSpanner.bound-details.right.text = #"right text"
2123 @cindex reverting overrides
2124 @cindex overrides, reverting
2126 The effects of @code{\override} can be undone by @code{\revert}.
2128 The syntax for the @code{\revert} command is
2131 \revert [@var{context}.]@var{GrobName}.@var{property}
2136 @lilypond[quote,verbatim,relative=2]
2138 \override Voice.Stem.thickness = #3.0
2140 \revert Voice.Stem.thickness
2144 The effects of @code{\override} and @code{\revert} apply to all
2145 grobs in the affected context from the current time forward:
2147 @lilypond[quote,verbatim,relative=2]
2152 \override Staff.Stem.thickness = #3.0
2156 \revert Staff.Stem.thickness
2164 @cindex overriding for only one moment
2166 @code{\once} can be used with @code{\override}
2167 to affect only the current time step:
2169 @lilypond[quote,verbatim,relative=2]
2173 \override Stem.thickness = #3.0
2177 \once \override Stem.thickness = #3.0
2186 Commands which change output generally look like
2189 \override Voice.Stem.thickness = #3.0
2193 To construct this tweak we must determine these bits of information:
2196 @item the context: here @code{Voice}.
2197 @item the layout object: here @code{Stem}.
2198 @item the layout property: here @code{thickness}.
2199 @item a sensible value: here @code{3.0}.
2202 @cindex internal documentation
2203 @cindex finding graphical objects
2204 @cindex graphical object descriptions
2207 @cindex internal documentation
2209 For many properties, regardless of the data type of the property, setting the
2210 property to false (@code{#f}) will result in turning it off, causing
2211 LilyPond to ignore that property entirely. This is particularly useful for
2212 turning off grob properties which may otherwise be causing problems.
2214 We demonstrate how to glean this information from the notation manual
2215 and the program reference.
2219 Internals Reference:
2220 @rinternals{Backend}
2223 @node The tweak command
2224 @subsection The @code{\tweak} command
2229 Changing grob properties
2230 with @code{\override} causes the changes to apply to all of the
2231 given grobs in the context at the moment the change applies.
2232 Sometimes, however, it is desirable to have changes apply to just
2233 one grob, rather than to all grobs in the affected context. This is
2234 accomplished with the @code{\tweak} command, which has the following
2238 \tweak [@var{layout-object}.]@var{grob-property} @var{value}
2241 Specifying @var{layout-object} is optional.
2242 The @code{\tweak} command applies to the music object that immediately
2243 follows @var{value} in the music stream.
2246 In some cases, it is possible to take a short-cut for tuning
2247 graphical objects. For objects that are created directly from
2248 an item in the input file, you can use the @code{\tweak} command.
2251 @lilypond[relative=2,verbatim,quote]
2256 \tweak duration-log #1
2265 The main use of the @code{\tweak} command is to modify just
2266 one of a number of notation elements which start at the same musical
2267 moment, like the notes of a chord, or tuplet brackets which start
2270 The @code{\tweak} command sets a property in the following object
2271 directly, without requiring the grob name or context to be
2272 specified. For this to work, it is necessary for the @code{\tweak}
2273 command to remain immediately adjacent to the object to which it is
2274 to apply after the input file has been converted to a music stream.
2275 This is often not the case, as many additional elements are inserted
2276 into the music stream implicitly. For example, when a note which is
2277 not part of a chord is processed, LilyPond implicitly inserts a
2278 @code{ChordEvent} event before the note, so separating the tweak
2279 from the note. However, if chord symbols are placed round the
2280 tweak and the note, the @code{\tweak} command comes after the
2281 @code{ChordEvent} in the music stream, so remaining adjacent to the
2282 note, and able to modify it.
2286 @lilypond[relative=2,verbatim,quote]
2287 <\tweak color #red c>4
2293 @lilypond[relative=2,verbatim,quote]
2294 \tweak color #red c4
2299 For an introduction to the syntax and uses of the tweak command
2300 see @rlearning{Tweaking methods}.
2302 When several similar items are placed at the same musical moment,
2303 the @code{\override} command cannot be used to modify just one of
2304 them -- this is where the @code{\tweak} command must be used.
2305 Items which may appear more than once at the same musical moment
2306 include the following:
2308 @c TODO expand to include any further uses of \tweak
2310 @item note heads of notes inside a chord
2311 @item articulation signs on a single note
2312 @item ties between notes in a chord
2313 @item tuplet brackets starting at the same time
2316 @c TODO add examples of these
2318 @cindex chord, modifying one note in
2320 In this example, the color of one note head and the type of another
2321 note head are modified within a single chord:
2323 @lilypond[relative=2,verbatim,quote]
2328 \tweak duration-log #1
2333 @code{\tweak} can be used to modify slurs:
2335 @lilypond[verbatim,quote,relative=1]
2336 c-\tweak thickness #5 ( d e f)
2340 For the @code{\tweak} command to work, it must
2341 remain immediately adjacent to the object to which it is
2342 to apply after the input file has been converted to a music stream.
2343 Tweaking a whole chord does not do anything since its music event
2344 only acts as a container, and all layout objects are created from events
2345 inside of the @code{EventChord}:
2347 @lilypond[relative=2,verbatim,quote]
2348 \tweak color #red c4
2349 \tweak color #red <c e>4
2350 <\tweak color #red c e>4
2353 The simple @code{\tweak} command cannot be used to modify any object
2354 that is not directly created from the input. In particular
2355 it will not affect stems, automatic
2356 beams or accidentals, since these are generated later by
2357 @code{NoteHead} layout objects rather than by music elements in the
2360 Such indirectly created layout objects can be tweaked using the form
2361 of the @code{\tweak} command in which the grob name is specified
2364 @lilypond[relative=2,verbatim,quote]
2365 \tweak Stem.color #red
2366 \tweak Beam.color #green c8 e
2367 <c e \tweak Accidental.font-size #-3 ges>4
2370 @code{\tweak} cannot be used to modify clefs or time
2371 signatures, since these become separated from any preceding
2372 @code{\tweak} command in the input stream by the automatic
2373 insertion of extra elements required to specify the context.
2375 Several @code{\tweak} commands may be placed before a
2376 notational element -- all affect it:
2378 @lilypond[verbatim,quote,relative=1]
2380 -\tweak style #'dashed-line
2381 -\tweak dash-fraction #0.2
2382 -\tweak thickness #3
2388 The music stream which is generated from a section of an input file,
2389 including any automatically inserted elements, may be examined,
2390 see @rextend{Displaying music expressions}. This may be helpful in
2391 determining what may be modified by a @code{\tweak} command, or
2392 in determining how to adjust the input to make a @code{\tweak}
2397 @rlearning{Tweaking methods}.
2400 @rextend{Displaying music expressions}.
2404 @cindex tweaking control points
2405 @cindex control points, tweaking
2407 The @code{\tweak} command cannot be used to modify the control
2408 points of just one of several ties in a chord, other than the first
2409 one encountered in the input file.
2411 @node set versus override
2412 @subsection @code{\set} vs. @code{\override}
2414 @c TODO Should't a bunch of that be explained earlier?
2418 Both @code{\set} and @code{\override} manipulate properties
2419 associated with contexts. In either case, properties heed the
2420 hierarchy of contexts: properties not set in a context itself show
2421 the values of the respective parent context.
2423 Values and lifetime of context properties are dynamic and only
2424 available when music is being interpreted, @q{iterated}. At the
2425 time of context creation, properties are initialized from the
2426 corresponding context definition and possible context
2427 modifications. Afterwards, changes are achieved with
2428 property-setting commands in the music itself.
2430 Now grob definitions are a special category of context properties.
2431 Since their structure, bookkeeping and use is different from
2432 ordinary context properties, they are accessed with a different
2433 set of commands, and treated separately in the documentation.
2435 As opposed to plain context properties, grob definitions are
2436 subdivided into grob properties. A @qq{grob} (graphical object)
2437 is usually created by an engraver at the time of interpreting a
2438 music expression and receives its initial properties from the
2439 current grob definition of the engraver's context. The engraver
2440 (or other @q{backend} parts of LilyPond) may subsequently add or
2441 change properties to the grob, but that does not affect the
2442 context's grob definition.
2444 What we call @q{grob properties} in the context of user-level
2445 tweaking are actually the properties of a context's grob
2446 definition. In contrast to ordinary context properties, grob
2447 definitions have the bookkeeping required to keep track of its
2448 parts, the individual grob properties (and even subproperties of
2449 them) separately so that it is possible to define those parts in
2450 different contexts and have the overall grob definition at the
2451 time of grob creation be assembled from pieces provided in
2452 different contexts among the current context and its parents.
2454 Grob definitions are manipulated using @code{\override} and
2455 @code{\revert} and have a name starting with a capital letter
2456 (like @samp{NoteHead}) whereas ordinary context properties are
2457 manipulated using @code{\set} and @code{\unset} and are named
2458 starting with a lowercase letter.
2460 @cindex tweak, relation to @code{\override}
2462 @funindex \overrideProperty
2463 The special commands @code{\tweak} and @code{\overrideProperty}
2464 change grob properties bypassing context properties completely.
2465 Instead they catch grobs as they are being created and then
2466 directly set properties on them when they originate from a tweaked
2467 music event or are of a particular kind, respectively.
2469 @node Modifying alists
2470 @subsection Modifying alists
2472 Some user-configurable properties are internally represented as
2473 @emph{alists} (association lists), which store pairs of
2474 @emph{keys} and @emph{values}. The structure of an alist is:
2477 '((@var{key1} . @var{value1})
2478 (@var{key2} . @var{value2})
2479 (@var{key3} . @var{value3})
2483 If an alist is a grob property or @code{\paper} variable, its keys
2484 can be modified individually without affecting other keys.
2486 For example, to reduce the space between adjacent staves in a
2487 staff-group, use the @code{staff-staff-spacing} property of the
2488 @code{StaffGrouper} grob. The property is an alist with four
2489 keys: @code{basic-distance}, @code{minimum-distance},
2490 @code{padding}, and @code{stretchability}. The standard settings
2491 for this property are listed in the @qq{Backend} section of the
2492 Internals Reference (see @rinternals{StaffGrouper}):
2495 '((basic-distance . 9)
2496 (minimum-distance . 7)
2498 (stretchability . 5))
2501 One way to bring the staves closer together is by reducing the
2502 value of the @code{basic-distance} key (@code{9}) to match the
2503 value of @code{minimum-distance} (@code{7}). To modify a single
2504 key individually, use a @emph{nested declaration}:
2506 @lilypond[quote,verbatim]
2507 % default space between staves
2509 \new Staff { \clef treble c''1 }
2510 \new Staff { \clef bass c1 }
2513 % reduced space between staves
2514 \new PianoStaff \with {
2515 % this is the nested declaration
2516 \override StaffGrouper.staff-staff-spacing.basic-distance = #7
2518 \new Staff { \clef treble c''1 }
2519 \new Staff { \clef bass c1 }
2523 Using a nested declaration will update the specified key (such as
2524 @code{basic-distance} in the above example) without altering any
2525 other keys already set for the same property.
2527 Now suppose we want the staves to be as close as possible without
2528 overlapping. The simplest way to do this is to set all four alist
2529 keys to zero. However, it is not necessary to enter four nested
2530 declarations, one for each key. Instead, the property can be
2531 completely re-defined with one declaration, as an alist:
2533 @lilypond[quote,verbatim]
2534 \new PianoStaff \with {
2535 \override StaffGrouper.staff-staff-spacing =
2536 #'((basic-distance . 0)
2537 (minimum-distance . 0)
2539 (stretchability . 0))
2541 \new Staff { \clef treble c''1 }
2542 \new Staff { \clef bass c1 }
2546 Note that any keys not explicitly listed in the alist definition
2547 will be reset to their @emph{default-when-unset} values. In the
2548 case of @code{staff-staff-spacing}, any unset key-values would be
2549 reset to zero (except @code{stretchability}, which takes the value
2550 of @code{basic-distance} when unset). Thus the following two
2551 declarations are equivalent:
2554 \override StaffGrouper.staff-staff-spacing =
2555 #'((basic-distance . 7))
2557 \override StaffGrouper.staff-staff-spacing =
2558 #'((basic-distance . 7)
2559 (minimum-distance . 0)
2561 (stretchability . 7))
2564 One (possibly unintended) consequence of this is the removal of
2565 any standard settings that are set in an initialization file and
2566 loaded each time an input file is compiled. In the above example,
2567 the standard settings for @code{padding} and
2568 @code{minimum-distance} (defined in @file{scm/define-grobs.scm})
2569 are reset to their default-when-unset values (zero for both keys).
2570 Defining a property or variable as an alist (of any size) will
2571 always reset all unset key-values to their default-when-unset
2572 values. Unless this is the intended result, it is safer to update
2573 key-values individually with a nested declaration.
2575 @warning{Nested declarations will not work for context property
2576 alists (such as @code{beamExceptions}, @code{keyAlterations},
2577 @code{timeSignatureSettings}, etc.). These properties can only be
2578 modified by completely re-defining them as alists.}
2581 @node Useful concepts and properties
2582 @section Useful concepts and properties
2587 * Direction and placement::
2588 * Distances and measurements::
2589 * Staff symbol properties::
2591 * Visibility of objects::
2593 * Rotating objects::
2597 @subsection Input modes
2599 The way in which the notation contained within an input file is
2600 interpreted is determined by the current input mode.
2602 @subsubsubheading Chord mode
2604 This is activated with the @code{\chordmode} command, and causes
2605 input to be interpreted with the syntax of chord notation, see
2606 @ref{Chord notation}. Chords are rendered as notes on a staff.
2608 Chord mode is also activated with the @code{\chords} command.
2609 This also creates a new @code{ChordNames} context and
2610 causes the following input to be interpreted with the syntax of
2611 chord notation and rendered as chord names in the @code{ChordNames}
2612 context, see @ref{Printing chord names}.
2614 @subsubsubheading Drum mode
2616 This is activated with the @code{\drummode} command, and causes
2617 input to be interpreted with the syntax of drum notation, see
2618 @ref{Basic percussion notation}.
2620 Drum mode is also activated with the @code{\drums} command.
2621 This also creates a new @code{DrumStaff} context and causes the
2622 following input to be interpreted with the syntax of drum notation
2623 and rendered as drum symbols on a drum staff, see
2624 @ref{Basic percussion notation}.
2626 @subsubsubheading Figure mode
2628 This is activated with the @code{\figuremode} command, and causes
2629 input to be interpreted with the syntax of figured bass, see
2630 @ref{Entering figured bass}.
2632 Figure mode is also activated with the @code{\figures} command.
2633 This also creates a new @code{FiguredBass} context and causes the
2634 following input to be interpreted with the figured bass syntax
2635 and rendered as figured bass symbols in the @code{FiguredBass}
2636 context, see @ref{Introduction to figured bass}.
2638 @subsubsubheading Fret and tab modes
2640 There are no special input modes for entering fret and tab symbols.
2642 To create tab diagrams, enter notes or chords in note mode and
2643 render them in a @code{TabStaff} context, see
2644 @ref{Default tablatures}.
2646 To create fret diagrams above a staff, you have two choices.
2647 You can either use the @code{FretBoards} context (see
2648 @ref{Automatic fret diagrams} or you can enter them as a markup
2649 above the notes using the @code{\fret-diagram} command (see
2650 @ref{Fret diagram markups}).
2652 @subsubsubheading Lyrics mode
2654 This is activated with the @code{\lyricmode} command, and causes
2655 input to be interpreted as lyric syllables with optional durations
2656 and associated lyric modifiers, see @ref{Vocal music}.
2658 Lyric mode is also activated with the @code{\addlyrics} command.
2659 This also creates a new @code{Lyrics} context and an implicit
2660 @code{\lyricsto} command which associates the following lyrics
2661 with the preceding music.
2663 @subsubsubheading Markup mode
2665 This is activated with the @code{\markup} command, and causes
2666 input to be interpreted with the syntax of markup, see
2667 @ref{Text markup commands}.
2669 @subsubsubheading Note mode
2671 This is the default mode or it may be activated with the
2672 @code{\notemode} command. Input is interpreted as pitches,
2673 durations, markup, etc and typeset as musical notation on a staff.
2675 It is not normally necessary to specify note mode explicitly, but
2676 it may be useful to do so in certain situations, for example if you
2677 are in lyric mode, chord mode or any other mode and want to insert
2678 something that only can be done with note mode syntax.
2681 @node Direction and placement
2682 @subsection Direction and placement
2684 In typesetting music the direction and placement of many items is
2685 a matter of choice. For example, the stems of notes can
2686 be directed up or down; lyrics, dynamics, and other expressive
2687 marks may be placed above or below the staff; text may be aligned
2688 left, right or center; etc. Most of these choices may be left to
2689 be determined automatically by LilyPond, but in some cases it may
2690 be desirable to force a particular direction or placement.
2693 * Articulation direction indicators::
2694 * The direction property::
2697 @node Articulation direction indicators
2698 @unnumberedsubsubsec Articulation direction indicators
2700 By default some directions are always up or always down (e.g.
2701 dynamics or fermata), while other things can alternate between
2702 up or down based on the stem direction (like slurs or accents).
2704 @c TODO Add table showing these
2706 The default action may be overridden by prefixing the articulation
2707 by a @emph{direction indicator}. Three direction indicators are
2708 available: @code{^} (meaning @qq{up}), @code{_} (meaning @qq{down})
2709 and @code{-} (meaning @qq{use default direction}). The direction
2710 indicator can usually be omitted, in which case @code{-} is assumed,
2711 but a direction indicator is @strong{always} required before
2714 @item @code{\tweak} commands
2715 @item @code{\markup} commands
2716 @item @code{\tag} commands
2717 @item string markups, e.g. -"string"
2718 @item fingering instructions, e.g. @w{@code{-1}}
2719 @item articulation shortcuts, e.g. @w{@code{-.}}, @w{@code{->}}, @w{@code{--}}
2722 Direction indicators affect only the next note:
2724 @lilypond[verbatim,quote,relative=2]
2731 @node The direction property
2732 @unnumberedsubsubsec The direction property
2734 The position or direction of many layout objects is controlled by the
2735 @code{direction} property.
2737 The value of the @code{direction} property may be set to @code{1},
2738 meaning @qq{up} or @qq{above}, or to @w{@code{-1}}, meaning @qq{down} or
2739 @qq{below}. The symbols @code{UP} and @code{DOWN} may be used instead
2740 of @code{1} and @w{@code{-1}} respectively. The default direction may
2741 be specified by setting @code{direction} to @code{0} or @code{CENTER}.
2742 Alternatively, in many cases predefined commands exist to specify the
2743 direction. These are of the form
2746 @code{\xxxUp}, @code{\xxxDown} or @code{\xxxNeutral}
2750 where @code{\xxxNeutral} means @qq{use the default} direction.
2751 See @rlearning{Within-staff objects}.
2753 In a few cases, arpeggio for example, the value of the @code{direction}
2754 property can specify whether the object is to be placed to the right or
2755 left of the parent. In this case @w{@code{-1}} or @code{LEFT} means
2756 @qq{to the left} and @code{1} or @code{RIGHT} means @qq{to the right}.
2757 @code{0} or @code{CENTER} means @qq{use the default} direction.
2760 These all have side-axis set to #X
2761 AmbitusAccidental - direction has no effect
2763 StanzaNumber - not tried
2764 TrillPitchAccidental - not tried
2765 TrillPitchGroup - not tried
2768 These indications affect all notes until they are canceled.
2770 @lilypond[verbatim,quote,relative=2]
2779 In polyphonic music, it is generally better to specify an explicit
2780 @code{voice} than change an object's direction. For more information.
2781 See @ref{Multiple voices}.
2785 @rlearning{Within-staff objects}.
2788 @ref{Multiple voices}.
2791 @node Distances and measurements
2792 @subsection Distances and measurements
2794 @cindex distances, absolute
2795 @cindex distances, scaled
2802 Distances in LilyPond are of two types: absolute and scaled.
2804 Absolute distances are used for specifying margins, indents, and
2805 other page layout details, and are by default specified in
2806 millimeters. Distances may be specified in other units by
2807 following the quantity by @code{\mm}, @code{\cm},
2808 @code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27 of
2809 an inch). Page layout distances can also be specified in scalable
2810 units (see the following paragraph) by appending
2811 @code{\staff-space} to the quantity. Page layout is described in
2812 detail in @ref{Page layout}.
2814 Scaled distances are always specified in units of the staff-space
2815 or, rarely, the half staff-space. The staff-space is the distance
2816 between two adjacent staff lines. The default value can be changed
2817 globally by setting the global staff size, or it can be overridden
2818 locally by changing the @code{staff-space} property of
2819 @code{StaffSymbol}. Scaled distances automatically scale with any
2820 change to the either the global staff size or the
2821 @code{staff-space} property of @code{StaffSymbol}, but fonts scale
2822 automatically only with changes to the global staff size.
2823 The global staff size thus enables the overall size of a rendered
2824 score to be easily varied. For the methods of setting the global
2825 staff size see @ref{Setting the staff size}.
2829 If just a section of a score needs to be rendered to a different
2830 scale, for example an ossia section or a footnote, the global staff
2831 size cannot simply be changed as this would affect the entire score.
2832 In such cases the change in size is made by overriding both the
2833 @code{staff-space} property of @code{StaffSymbol} and the size of
2834 the fonts. A Scheme function, @code{magstep}, is available to
2835 convert from a font size change to the equivalent change in
2836 @code{staff-space}. For an explanation and an example of its use,
2837 see @rlearning{Length and thickness of objects}.
2841 @rlearning{Length and thickness of objects}.
2845 @ref{Setting the staff size}.
2848 @node Staff symbol properties
2849 @subsection Staff symbol properties
2851 @cindex adjusting staff symbol
2852 @cindex drawing staff symbol
2853 @cindex staff symbol, setting of
2855 @c TODO Extend or remove this section. See also NR 1.6.2 Staff symbol
2856 @c Need to think of uses for these properties. Eg 'line-positions
2857 @c is used in a snippet to thicken centre line.
2858 @c If retained, add @ref to here in 1.6.2 -td
2860 The vertical position of staff lines and the number of staff lines
2861 can be defined at the same time. As the following example shows,
2862 note positions are not influenced by the staff line positions.
2864 @warning{The @code{'line-positions} property overrides the
2865 @code{'line-count} property. The number of staff lines is
2866 implicitly defined by the number of elements in the list of values
2867 for @code{'line-positions}.}
2869 @lilypond[verbatim,quote,relative=1]
2871 \override StaffSymbol.line-positions = #'(7 3 0 -4 -6 -7)
2876 The width of a staff can be modified. The units are staff
2877 spaces. The spacing of objects inside the staff is not affected by
2880 @lilypond[verbatim,quote,relative=1]
2882 \override StaffSymbol.width = #23
2889 @subsection Spanners
2891 Many objects of musical notation extend over several notes or even
2892 several bars. Examples are slurs, beams, tuplet brackets, volta
2893 repeat brackets, crescendi, trills, and glissandi. Such objects
2894 are collectively called @qq{spanners}, and have special properties to control
2895 their appearance and behaviour. Some of these properties are common
2896 to all spanners; others are restricted to a sub-set of the spanners.
2898 All spanners support the @code{spanner-interface}. A few, essentially
2899 those that draw a straight line between the two objects, support in
2900 addition the @code{line-spanner-interface}.
2903 * Using the spanner-interface::
2904 * Using the line-spanner-interface::
2907 @node Using the spanner-interface
2908 @unnumberedsubsubsec Using the @code{spanner-interface}
2910 This interface provides two properties that apply to several spanners.
2912 @subsubsubheading The @code{minimum-length} property
2914 The minimum length of the spanner is specified by the
2915 @code{minimum-length} property. Increasing this usually has the
2916 necessary effect of increasing the spacing of the notes between the
2917 two end points. However, this override has no effect on
2918 many spanners, as their length is determined by other considerations.
2919 A few examples where it is effective are shown below.
2929 Works as long as callback is made:
2933 Works not at all for:
2942 @lilypond[verbatim,quote,relative=2]
2945 % increase the length of the tie
2946 -\tweak minimum-length #5
2950 @lilypond[verbatim,quote,relative=2]
2952 \compressFullBarRests
2954 % increase the length of the rest bar
2955 \once \override MultiMeasureRest.minimum-length = #20
2960 @lilypond[verbatim,quote,relative=2]
2962 % increase the length of the hairpin
2963 \override Hairpin.minimum-length = #20
2967 This override can also be used to increase the length of slurs and
2970 @lilypond[verbatim,quote,relative=2]
2973 -\tweak minimum-length #5
2978 -\tweak minimum-length #5
2982 For some layout objects, the @code{minimum-length} property becomes
2983 effective only if the @code{set-spacing-rods} procedure is called
2984 explicitly. To do this, the @code{springs-and-rods} property should
2985 be set to @code{ly:spanner::set-spacing-rods}. For example,
2986 the minimum length of a glissando has no effect unless the
2987 @code{springs-and-rods} property is set:
2989 @lilypond[verbatim,quote,relative=1]
2993 % not effective alone
2994 \once \override Glissando.minimum-length = #20
2997 % effective only when both overrides are present
2998 \once \override Glissando.minimum-length = #20
2999 \once \override Glissando.springs-and-rods = #ly:spanner::set-spacing-rods
3003 The same is true of the @code{Beam} object:
3005 @lilypond[verbatim,quote,relative=1]
3006 % not effective alone
3007 \once \override Beam.minimum-length = #20
3010 % effective only when both overrides are present
3011 \once \override Beam.minimum-length = #20
3012 \once \override Beam.springs-and-rods = #ly:spanner::set-spacing-rods
3016 @subsubsubheading The @code{to-barline} property
3018 The second useful property of the @code{spanner-interface} is
3019 @code{to-barline}. By default this is true, causing hairpins and
3020 other spanners which are terminated on the first note of a measure to
3021 end instead on the immediately preceding bar line. If set to false,
3022 the spanner will extend beyond the bar line and end on the note
3025 @lilypond[verbatim,quote,relative=2]
3026 a \< a a a a \! a a a \break
3027 \override Hairpin.to-barline = ##f
3028 a \< a a a a \! a a a
3031 This property is not effective for all spanners. For example,
3032 setting it to @code{#t} has no effect on slurs or phrasing slurs
3033 or on other spanners for which terminating on the bar line would
3036 @node Using the line-spanner-interface
3037 @unnumberedsubsubsec Using the @code{line-spanner-interface}
3039 Objects which support the @code{line-spanner-interface} include
3042 @item @code{DynamicTextSpanner}
3043 @item @code{Glissando}
3044 @item @code{TextSpanner}
3045 @item @code{TrillSpanner}
3046 @item @code{VoiceFollower}
3049 The routine responsible for drawing the stencils for these spanners is
3050 @code{ly:line-interface::print}. This routine determines the
3051 exact location of the two end points and draws a line
3052 between them, in the style requested. The locations of the two
3053 end points of the spanner are computed on-the-fly, but it is
3054 possible to override their Y-coordinates. The
3055 properties which need to be specified are nested
3056 two levels down within the property hierarchy, but the syntax of
3057 the @code{\override} command is quite simple:
3059 @lilypond[relative=2,quote,verbatim]
3061 \once \override Glissando.bound-details.left.Y = #3
3062 \once \override Glissando.bound-details.right.Y = #-2
3066 The units for the @code{Y} property are @code{staff-space}s,
3067 with the center line of the staff being the zero point.
3068 For the glissando, this is the value for @code{Y} at the
3069 X-coordinate corresponding to the center point of each note head,
3070 if the line is imagined to be extended to there.
3072 If @code{Y} is not set, the value is computed from the vertical
3073 position of the corresponding attachment point of the spanner.
3075 In case of a line break, the values for the end points are
3076 specified by the @code{left-broken} and @code{right-broken}
3077 sub-lists of @code{bound-details}. For example:
3079 @lilypond[relative=2,ragged-right,verbatim,quote]
3080 \override Glissando.breakable = ##t
3081 \override Glissando.bound-details.right-broken.Y = #-3
3082 c1 \glissando \break
3087 A number of further properties of the @code{left} and
3088 @code{right} sub-lists of the @code{bound-details} property
3089 may be modified in the same way as @code{Y}:
3093 This sets the Y-coordinate of the end point, in @code{staff-space}s
3094 offset from the staff center line. By default, it is the center of
3095 the bound object, so a glissando points to the vertical center of
3098 For horizontal spanners, such as text spanners and trill spanners,
3099 it is hardcoded to 0.
3102 This determines where the line starts and ends in the X-direction,
3103 relative to the bound object. So, a value of @w{@code{-1}} (or
3104 @code{LEFT}) makes the line start/end at the left side of the note
3105 head it is attached to.
3108 This is the absolute X-coordinate of the end point. It is usually
3109 computed on the fly, and overriding it has little useful effect.
3112 Line spanners may have symbols at the beginning or end, which is
3113 contained in this sub-property. This is for internal use; it is
3114 recommended that @code{text} be used instead.
3117 This is a markup that is evaluated to yield the stencil. It is used
3118 to put @i{cresc.}, @i{tr} and other text on horizontal spanners.
3120 @lilypond[quote,ragged-right,relative=2,verbatim]
3121 \override TextSpanner.bound-details.left.text
3122 = \markup { \small \bold Slower }
3123 c2\startTextSpan b c a\stopTextSpan
3126 @item stencil-align-dir-y
3127 @item stencil-offset
3128 Without setting one of these, the stencil is simply put at the
3129 end-point, centered on the line, as defined by the @code{X} and
3130 @code{Y} sub-properties. Setting either @code{stencil-align-dir-y}
3131 or @code{stencil-offset} will move the symbol at the edge vertically
3132 relative to the end point of the line:
3134 @lilypond[relative=1,quote,verbatim]
3135 \override TextSpanner.bound-details.left.stencil-align-dir-y = #-2
3136 \override TextSpanner.bound-details.right.stencil-align-dir-y = #UP
3138 \override TextSpanner.bound-details.left.text = #"ggg"
3139 \override TextSpanner.bound-details.right.text = #"hhh"
3140 c4^\startTextSpan c c c \stopTextSpan
3143 Note that negative values move the text @emph{up}, contrary to the
3144 effect that might be expected, as a value of @w{@code{-1}} or
3145 @code{DOWN} means align the @emph{bottom} edge of the text with
3146 the spanner line. A value of @code{1} or @code{UP} aligns
3147 the top edge of the text with the spanner line.
3150 Setting this sub-property to @code{#t} produces an arrowhead at the
3154 This sub-property controls the space between the specified
3155 end point of the line and the actual end. Without padding, a
3156 glissando would start and end in the center of each note head.
3160 The music function @code{\endSpanners} terminates the spanner
3161 which starts on the immediately following note prematurely. It
3162 is terminated after exactly one note, or at the following bar line
3163 if @code{to-barline} is true and a bar line occurs before the next
3166 @lilypond[verbatim,quote,ragged-right,relative=2]
3168 c2 \startTextSpan c2 c2
3173 When using @code{\endSpanners} it is not necessary to close
3174 \startTextSpan with \stopTextSpan, nor is it necessary to close
3175 hairpins with @code{\!}.
3178 Internals Reference:
3179 @rinternals{TextSpanner},
3180 @rinternals{Glissando},
3181 @rinternals{VoiceFollower},
3182 @rinternals{TrillSpanner},
3183 @rinternals{line-spanner-interface}.
3186 @node Visibility of objects
3187 @subsection Visibility of objects
3189 @cindex objects, visibility of
3190 @cindex grobs, visibility of
3191 @cindex visibility of objects
3193 There are four main ways in which the visibility of layout objects
3194 can be controlled: their stencil can be removed, they can be made
3195 transparent, they can be colored white, or their
3196 @code{break-visibility} property can be overridden. The first
3197 three apply to all layout objects; the last to just a few -- the
3198 @emph{breakable} objects. The Learning Manual introduces these
3199 four techniques, see @rlearning{Visibility and color of objects}.
3201 There are also a few other techniques which are specific to
3202 certain layout objects. These are covered under Special
3206 * Removing the stencil::
3207 * Making objects transparent::
3208 * Painting objects white::
3209 * Using break-visibility::
3210 * Special considerations::
3214 @node Removing the stencil
3215 @unnumberedsubsubsec Removing the stencil
3217 @cindex stencil, removing
3220 Every layout object has a stencil property. By default this is set
3221 to the specific function which draws that object. If this property
3222 is overridden to @code{#f} no function will be called and the object
3223 will not be drawn. The default action can be recovered with
3226 @lilypond[quote,verbatim,relative=1]
3228 \override Score.BarLine.stencil = ##f
3230 \revert Score.BarLine.stencil
3234 This rather common operation has a shortcut @code{\omit}:
3236 @lilypond[quote,verbatim,relative=1]
3240 \undo \omit Score.BarLine
3244 @node Making objects transparent
3245 @unnumberedsubsubsec Making objects transparent
3247 @cindex transparent, making objects
3250 Every layout object has a transparent property which by default is
3251 set to @code{#f}. If set to @code{#t} the object still occupies
3252 space but is made invisible.
3254 @lilypond[quote,verbatim,relative=2]
3256 \once \override NoteHead.transparent = ##t
3260 This rather common operation has a shortcut @code{\hide}:
3262 @lilypond[quote,verbatim,relative=2]
3264 \once \hide NoteHead
3268 @node Painting objects white
3269 @unnumberedsubsubsec Painting objects white
3271 @cindex objects, coloring
3272 @cindex coloring objects
3274 @cindex printing order
3275 @cindex overwriting objects
3276 @cindex objects, overwriting
3277 @cindex grobs, overwriting
3279 Every layout object has a color property which by default is set
3280 to @code{black}. If this is overridden to @code{white} the object
3281 will be indistinguishable from the white background. However,
3282 if the object crosses other objects the color of the crossing
3283 points will be determined by the order in which they are drawn,
3284 and this may leave a ghostly image of the white object, as shown
3287 @lilypond[quote,verbatim,relative=2]
3288 \override Staff.Clef.color = #white
3292 This may be avoided by changing the order of printing the objects.
3293 All layout objects have a @code{layer} property which should be set
3294 to an integer. Objects with the lowest value of @code{layer} are
3295 drawn first, then objects with progressively higher values are drawn,
3296 so objects with higher values overwrite objects with lower values.
3297 By default most objects are assigned a @code{layer} value of
3298 @code{1}, although a few objects, including @code{StaffSymbol} and
3299 @code{BarLine}, are assigned a value of @code{0}. The order of
3300 printing objects with the same value of @code{layer} is indeterminate.
3302 In the example above the white clef, with a default @code{layer}
3303 value of @code{1}, is drawn after the staff lines (default
3304 @code{layer} value @code{0}), so overwriting them. To change this,
3305 the @code{Clef} object must be given in a lower value of
3306 @code{layer}, say @w{@code{-1}}, so that it is drawn earlier:
3308 @lilypond[quote,verbatim,relative=2]
3309 \override Staff.Clef.color = #white
3310 \override Staff.Clef.layer = #-1
3314 @node Using break-visibility
3315 @unnumberedsubsubsec Using break-visibility
3317 @c TODO Add making other objects breakable
3319 @cindex break-visibility
3321 Most layout objects are printed only once, but some like
3322 bar lines, clefs, time signatures and key signatures, may need
3323 to be printed twice when a line break occurs -- once at the end
3324 of the line and again at the start of the next line. Such
3325 objects are called @emph{breakable}, and have a property, the
3326 @code{break-visibility} property to control their visibility
3327 at the three positions in which they may appear -- at the
3328 start of a line, within a line if they are changed, and at the
3329 end of a line if a change takes place there.
3331 For example, the time signature
3332 by default will be printed at the start of the first line, but
3333 nowhere else unless it changes, when it will be printed at the
3334 point at which the change occurs. If this change occurs at the
3335 end of a line the new time signature will be printed at the start
3336 of the next line and a cautionary time signature will be printed
3337 at the end of the previous line as well.
3339 This behaviour is controlled by the @code{break-visibility}
3340 property, which is explained in
3341 @c Leave this ref on a newline - formats incorrectly otherwise -td
3342 @rlearning{Visibility and color of objects}. This property takes
3343 a vector of three booleans which, in order, determine whether the
3344 object is printed at the end of, within the body of, or at the
3345 beginning of a line. Or to be more precise, before a line break,
3346 where there is no line break, or after a line break.
3348 Alternatively, these eight combinations may be specified
3349 by pre-defined functions, defined in @file{scm/output-lib.scm},
3350 where the last three columns indicate whether the layout objects
3351 will be visible in the positions shown at the head of the columns:
3353 @multitable {@code{begin-of-line-invisible}} {@code{'#(#t #t #t)}} {Before} {At no} {After}
3354 @headitem Function @tab Vector @tab Before @tab At no @tab After
3355 @headitem form @tab form @tab break @tab break @tab break
3357 @item @code{all-visible} @tab @code{'#(#t #t #t)} @tab yes @tab yes @tab yes
3358 @item @code{begin-of-line-visible} @tab @code{'#(#f #f #t)} @tab no @tab no @tab yes
3359 @item @code{center-visible} @tab @code{'#(#f #t #f)} @tab no @tab yes @tab no
3360 @item @code{end-of-line-visible} @tab @code{'#(#t #f #f)} @tab yes @tab no @tab no
3361 @item @code{begin-of-line-invisible} @tab @code{'#(#t #t #f)} @tab yes @tab yes @tab no
3362 @item @code{center-invisible} @tab @code{'#(#t #f #t)} @tab yes @tab no @tab yes
3363 @item @code{end-of-line-invisible} @tab @code{'#(#f #t #t)} @tab no @tab yes @tab yes
3364 @item @code{all-invisible} @tab @code{'#(#f #f #f)} @tab no @tab no @tab no
3367 The default settings of @code{break-visibility} depend on the
3368 layout object. The following table shows all the layout objects
3369 of interest which are affected by @code{break-visibility} and the
3370 default setting of this property:
3372 @multitable @columnfractions .3 .3 .4
3374 @headitem Layout object @tab Usual context @tab Default setting
3376 @c omit Ambitus as it appears not to be affected by break-visibility -td
3377 @c @item @code{Ambitus} @tab as specified @tab @code{begin-of-line-visible}
3378 @item @code{BarLine} @tab @code{Score} @tab calculated
3379 @item @code{BarNumber} @tab @code{Score} @tab @code{begin-of-line-visible}
3380 @c omit the following item until it can be explained -td
3381 @c @item @code{BreakAlignGroup} @tab @code{Score} @tab calculated
3382 @item @code{BreathingSign} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3383 @item @code{Clef} @tab @code{Staff} @tab @code{begin-of-line-visible}
3384 @item @code{Custos} @tab @code{Staff} @tab @code{end-of-line-visible}
3385 @item @code{DoublePercentRepeat} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3386 @item @code{KeyCancellation} @tab @code{Staff} @tab @code{begin-of-line-invisible}
3387 @item @code{KeySignature} @tab @code{Staff} @tab @code{begin-of-line-visible}
3388 @c omit LeftEdge until it can be explained -td
3389 @c @item @code{LeftEdge} @tab @code{Score} @tab @code{center-invisible}
3390 @item @code{ClefModifier} @tab @code{Staff} @tab @code{begin-of-line-visible}
3391 @item @code{RehearsalMark} @tab @code{Score} @tab @code{end-of-line-invisible}
3392 @item @code{TimeSignature} @tab @code{Staff} @tab @code{all-visible}
3396 The example below shows the use of the vector form to control the
3397 visibility of bar lines:
3399 @lilypond[quote,verbatim,relative=1,ragged-right]
3402 % Remove bar line at the end of the current line
3403 \once \override Score.BarLine.break-visibility = ##(#f #t #t)
3409 Although all three components of the vector used to override
3410 @code{break-visibility} must be present, not all of them are
3411 effective with every layout object, and some combinations may
3412 even give errors. The following limitations apply:
3415 @item Bar lines cannot be printed at start of line.
3416 @item A bar number cannot be printed at the start of the first
3417 line unless it is set to be different from 1.
3418 @item Clef -- see below
3419 @item Double percent repeats are either all printed or all
3420 suppressed. Use begin-of line-invisible to print and
3421 all-invisible to suppress.
3422 @item Key signature -- see below
3423 @item ClefModifier -- see below
3426 @node Special considerations
3427 @unnumberedsubsubsec Special considerations
3429 @subsubsubheading Visibility following explicit changes
3431 @cindex key signature, visibility following explicit change
3432 @cindex explicitKeySignatureVisibility
3433 @cindex clef, visibility following explicit change
3434 @cindex explicitClefVisibility
3436 The @code{break-visibility} property controls the visibility of
3437 key signatures and changes of clef only at the start of lines,
3438 i.e. after a break. It has no effect on the visibility of the
3439 key signature or clef following an explicit key change or an
3440 explicit clef change within or at the end of a line. In the
3441 following example the key signature following the explicit change
3442 to B-flat major is still visible, even though @code{all-invisible}
3445 @lilypond[quote,verbatim,relative=1,ragged-right]
3448 % Try to remove all key signatures
3449 \override Staff.KeySignature.break-visibility = #all-invisible
3457 The visibility of such explicit key signature and clef changes is
3458 controlled by the @code{explicitKeySignatureVisibility} and
3459 @code{explicitClefVisibility} properties. These are the equivalent
3460 of the @code{break-visibility} property and both take a vector of
3461 three booleans or the predefined functions listed above, exactly like
3462 @code{break-visibility}. Both are properties of the Staff context,
3463 not the layout objects themselves, and so they are set using the
3464 @code{\set} command. Both are set by default to @code{all-visible}.
3465 These properties control only the visibility of key signatures and
3466 clefs resulting from explicit changes and do not affect key
3467 signatures and clefs at the beginning of lines;
3468 @code{break-visibility} must still be overridden in the appropriate
3469 object to remove these.
3471 @lilypond[quote,verbatim,relative=1,ragged-right]
3474 \set Staff.explicitKeySignatureVisibility = #all-invisible
3475 \override Staff.KeySignature.break-visibility = #all-invisible
3482 @subsubsubheading Visibility of cancelling accidentals
3484 To remove the cancelling accidentals printed at an explicit key
3485 change, set the Staff context property @code{printKeyCancellation}
3488 @lilypond[quote,verbatim,relative=1,ragged-right]
3491 \set Staff.explicitKeySignatureVisibility = #all-invisible
3492 \set Staff.printKeyCancellation = ##f
3493 \override Staff.KeySignature.break-visibility = #all-invisible
3500 With these overrides only the accidentals before the notes remain
3501 to indicate the change of key.
3503 Note that when changing the key to C@tie{}major or A@tie{}minor
3504 the cancelling accidentals would be the @emph{only} indication of
3505 the key change. In this case setting @code{printKeyCancellation} to
3506 @code{#f} has no effect:
3508 @lilypond[quote,verbatim,relative=1,ragged-right]
3511 \set Staff.explicitKeySignatureVisibility = #all-invisible
3512 \set Staff.printKeyCancellation = ##f
3519 To suppress the cancelling accidentals even when the key is
3520 changed to C@tie{}major or A@tie{}minor, override
3521 the visibility of the @code{KeyCancellation} grob instead:
3523 @lilypond[quote,verbatim,relative=1,ragged-right]
3526 \set Staff.explicitKeySignatureVisibility = #all-invisible
3527 \override Staff.KeyCancellation.break-visibility = #all-invisible
3534 @c TODO Add visibility of cautionary accidentals before notes
3536 @subsubsubheading Automatic bars
3538 @cindex automaticBars
3539 @cindex bar lines, suppressing
3541 As a special case, the printing of bar lines can also be turned off
3542 by setting the @code{automaticBars} property in the Score context.
3543 If set to @code{#f}, bar lines will not be printed automatically;
3544 they must be explicitly created with a @code{\bar} command. Unlike
3545 the @code{\cadenzaOn} predefined command, measures are still counted.
3546 Bar generation will resume according to that count if this property
3547 is later set to @code{#t}. When set to @code{#f}, line breaks can
3548 occur only at explicit @code{\bar} commands.
3552 @subsubsubheading Transposed clefs
3554 @cindex transposed clefs, visibility of
3555 @cindex visibility of transposed clefs
3556 @cindex clefs, visibility of transposition
3558 The small transposition symbol on transposed clefs is produced by the
3559 @code{ClefModifier} layout object. Its visibility is automatically
3560 inherited from the @code{Clef} object, so it is not necessary to apply
3561 any required @code{break-visibility} overrides to the @code{ClefModifier}
3562 layout objects to suppress transposition symbols for invisible clefs.
3564 For explicit clef changes, the @code{explicitClefVisibility}
3565 property controls both the clef symbol and any transposition symbol
3570 @rlearning{Visibility and color of objects}.
3574 @subsection Line styles
3576 Some performance indications, e.g., @i{rallentando} and
3577 @i{accelerando} and @i{trills} are written as text and are
3578 extended over many measures with lines, sometimes dotted or wavy.
3580 These all use the same routines as the glissando for drawing the
3581 texts and the lines, and tuning their behavior is therefore also
3582 done in the same way. It is done with a spanner, and the routine
3583 responsible for drawing the spanners is
3584 @code{ly:line-interface::print}. This routine determines the
3585 exact location of the two @i{span points} and draws a line
3586 between them, in the style requested.
3588 Here is an example showing the different line styles available,
3589 and how to tune them.
3591 @lilypond[relative=2,ragged-right,verbatim,quote]
3593 \once \override Glissando.style = #'dashed-line
3595 \override Glissando.style = #'dotted-line
3597 \override Glissando.style = #'zigzag
3599 \override Glissando.style = #'trill
3603 The locations of the end-points of the spanner are computed
3604 on-the-fly for every graphic object, but it is possible to
3608 @lilypond[relative=2,ragged-right,verbatim,quote]
3610 \once \override Glissando.bound-details.right.Y = #-2
3614 The value for @code{Y} is set to @w{@code{-2}} for the right end
3615 point. The left side may be similarly adjusted by specifying
3616 @code{left} instead of @code{right}.
3618 If @code{Y} is not set, the value is computed from the vertical
3619 position of the left and right attachment points of the spanner.
3621 Other adjustments of spanners are possible, for details, see
3624 @node Rotating objects
3625 @subsection Rotating objects
3627 Both layout objects and elements of markup text can be rotated by
3628 any angle about any point, but the method of doing so differs.
3631 * Rotating layout objects::
3635 @node Rotating layout objects
3636 @unnumberedsubsubsec Rotating layout objects
3638 @cindex rotating objects
3639 @cindex objects, rotating
3641 All layout objects which support the @code{grob-interface} can be
3642 rotated by setting their @code{rotation} property. This takes a
3643 list of three items: the angle of rotation counter-clockwise,
3644 and the x and y coordinates of the point relative to the object's
3645 reference point about which the rotation is to be performed. The
3646 angle of rotation is specified in degrees and the coordinates in
3649 The angle of rotation and the coordinates of the rotation point must
3650 be determined by trial and error.
3652 @cindex hairpins, angled
3653 @cindex angled hairpins
3655 There are only a few situations where the rotation of layout
3656 objects is useful; the following example shows one situation where
3659 @lilypond[quote,verbatim,relative=1]
3661 \override Hairpin.rotation = #'(20 -1 0)
3665 @node Rotating markup
3666 @unnumberedsubsubsec Rotating markup
3668 All markup text can be rotated to lie at any angle by prefixing it
3669 with the @code{\rotate} command. The command takes two arguments:
3670 the angle of rotation in degrees counter-clockwise and the text to
3671 be rotated. The extents of the text are not rotated: they take
3672 their values from the extremes of the x and y coordinates of the
3673 rotated text. In the following example the
3674 @code{outside-staff-priority} property for text is set to @code{#f}
3675 to disable the automatic collision avoidance, which would push some
3676 of the text too high.
3678 @lilypond[quote,verbatim,relative=1]
3679 \override TextScript.outside-staff-priority = ##f
3680 g4^\markup { \rotate #30 "a G" }
3681 b^\markup { \rotate #30 "a B" }
3682 des^\markup { \rotate #30 "a D-Flat" }
3683 fis^\markup { \rotate #30 "an F-Sharp" }
3686 @node Advanced tweaks
3687 @section Advanced tweaks
3689 This section discusses various approaches to fine tuning the
3690 appearance of the printed score.
3693 * Aligning objects::
3694 * Vertical grouping of grobs::
3695 * Modifying stencils::
3696 * Modifying shapes::
3697 * Modifying broken spanners::
3698 * Unpure-pure containers::
3703 @rlearning{Tweaking output},
3704 @rlearning{Other sources of information}.
3707 @ref{Explaining the Internals Reference},
3708 @ref{Modifying properties}.
3711 @rextend{Interfaces for programmers}.
3714 @file{scm/define-grobs.scm}.
3717 @rlsr{Tweaks and overrides}.
3719 Internals Reference:
3720 @rinternals{All layout objects}.
3723 @node Aligning objects
3724 @subsection Aligning objects
3726 Graphical objects which support the @code{self-alignment-interface}
3727 and/or the @code{side-position-interface} can be aligned to a previously
3728 placed object in a variety of ways. For a list of these objects, see
3729 @rinternals{self-alignment-interface} and @rinternals{side-position-interface}.
3731 All graphical objects have a reference point, a horizontal extent and a
3732 vertical extent. The horizontal extent is a pair of numbers
3733 giving the displacements from the reference point of the left and
3734 right edges, displacements to the left being negative. The vertical
3735 extent is a pair of numbers giving the displacement from the reference
3736 point to the bottom and top edges, displacements down being negative.
3738 An object's position on a staff is given by the values of the
3739 @code{X-offset} and @code{Y-offset} properties. The value of
3740 @code{X-offset} gives the displacement from the X coordinate of
3741 the reference point of the parent object, and the value of
3742 @code{Y-offset} gives the displacement from the center line of the
3743 staff. The values of @code{X-offset} and @code{Y-offset} may
3744 be set directly or may be set to be calculated by procedures in order
3745 to achieve alignment with the parent object.
3747 @warning{Many objects have special positioning considerations which
3748 cause any setting of @code{X-offset} or @code{Y-offset} to be
3749 ignored or modified, even though the object supports the
3750 @code{self-alignment-interface}. Overriding the @code{X-offset}
3751 or @code{Y-offset} properties to a fixed value causes the respective
3752 @code{self-alignment} property to be disregarded.}
3754 For example, an accidental can be repositioned vertically by setting
3755 @code{Y-offset} but any changes to @code{X-offset} have no effect.
3757 Rehearsal marks may be aligned with breakable objects such as bar
3758 lines, clef symbols, time signature symbols and key signatures. There
3759 are special properties to be found in the @code{break-aligned-interface}
3760 for positioning rehearsal marks on such objects.
3764 @ref{Using the break-alignable-interface}.
3767 @rextend{Callback functions}.
3770 * Setting X-offset and Y-offset directly::
3771 * Using the side-position-interface::
3772 * Using the self-alignment-interface::
3773 * Using the break-alignable-interface::
3776 @node Setting X-offset and Y-offset directly
3777 @unnumberedsubsubsec Setting @code{X-offset} and @code{Y-offset} directly
3779 Numerical values may be given to the @code{X-offset} and @code{Y-offset}
3780 properties of many objects. The following example shows three
3781 notes with the default fingering position and the positions with @code{X-offset}
3782 and @code{Y-offset} modified.
3784 @lilypond[verbatim,quote,relative=2]
3791 -\tweak X-offset #-1
3798 @node Using the side-position-interface
3799 @unnumberedsubsubsec Using the @code{side-position-interface}
3801 An object which supports the @code{side-position-interface} can be
3802 placed next to its parent object so that
3803 the specified edges of the two objects touch. The object may be
3804 placed above, below, to the right or to the left of the parent.
3805 The parent cannot be specified; it is determined by the order of
3806 elements in the input stream. Most objects have the associated
3807 note head as their parent.
3809 The values of the @code{side-axis} and @code{direction} properties
3810 determine where the object is to be placed, as follows:
3812 @c TODO add an example of each to the table
3814 @multitable @columnfractions .3 .3 .3
3815 @headitem @code{side-axis} @tab @code{direction} @tab
3816 @headitem property @tab property @tab Placement
3818 @item @code{0} @tab @code{-1} @tab left
3819 @item @code{0} @tab @code{1} @tab right
3820 @item @code{1} @tab @code{-1} @tab below
3821 @item @code{1} @tab @code{1} @tab above
3825 When @code{side-axis} is @code{0}, @code{X-offset} should be set to
3826 the procedure @code{ly:side-position-interface::x-aligned-side}.
3827 This procedure will return the correct value of @code{X-offset} to
3828 place the object to the left or right side of the parent according
3829 to value of @code{direction}.
3831 When @code{side-axis} is @code{1}, @code{Y-offset} should be set to
3832 the procedure @code{ly:side-position-interface::y-aligned-side}.
3833 This procedure will return the correct value of @code{Y-offset} to
3834 place the object to the top or bottom of the parent according
3835 to value of @code{direction}.
3837 @c TODO Add examples
3839 @node Using the self-alignment-interface
3840 @unnumberedsubsubsec Using the @code{self-alignment-interface}
3842 @subsubsubheading Self-aligning objects horizontally
3844 The horizontal alignment of an object which supports the
3845 @code{self-alignment-interface} is controlled by the value of
3846 the @code{self-alignment-X} property, provided the object's
3847 @code{X-offset} property is set to
3848 @code{ly:self-alignment-interface::x-aligned-on-self}.
3849 @code{self-alignment-X} may be given any
3850 real value, in units of half the total X extent of the
3851 object. Negative values move the object to the right, positive
3852 to the left. A value of @code{0} centers the object on the
3853 reference point of its parent, a value of @w{@code{-1}} aligns the
3854 left edge of the object on the reference point of its parent,
3855 and a value of @code{1} aligns the right edge of the object on the
3856 reference point of its parent. The symbols @code{LEFT},
3857 @code{CENTER}, and @code{RIGHT} may be used instead of the values
3858 @w{@code{-1}}, @code{0}, and @code{1}, respectively.
3860 Normally the @code{\override} command would be used to modify the
3861 value of @code{self-alignment-X}, but the @code{\tweak} command
3862 can be used to separately align several annotations on a single
3865 @lilypond[quote,verbatim,relative=1]
3867 -\tweak self-alignment-X #-1
3869 -\tweak self-alignment-X #0
3871 -\tweak self-alignment-X #RIGHT
3873 -\tweak self-alignment-X #-2.5
3874 ^"aligned further to the right"
3877 @subsubsubheading Self-aligning objects vertically
3879 Objects may be aligned vertically in an analogous way to aligning
3880 them horizontally if the @code{Y-offset} property is set to
3881 @code{ly:self-alignment-interface::y-aligned-on-self}. However,
3882 other mechanisms are often involved in vertical alignment: the
3883 value of @code{Y-offset} is just one variable taken into account.
3884 This may make adjusting the value of some objects tricky.
3885 The units are just half the vertical extent of the object, which
3886 is usually quite small, so quite large numbers may be required.
3887 A value of @w{@code{-1}} aligns the lower edge of the object with
3888 the reference point of the parent object, a value of @code{0}
3889 aligns the center of the object with the reference point of the
3890 parent, and a value of @code{1} aligns the top edge of the object
3891 with the reference point of the parent. The symbols @code{DOWN},
3892 @code{CENTER}, and @code{UP} may be substituted for @w{@code{-1}},
3893 @code{0}, and @code{1}, respectively.
3895 @subsubsubheading Self-aligning objects in both directions
3897 By setting both @code{X-offset} and @code{Y-offset}, an object may
3898 be aligned in both directions simultaneously.
3900 The following example shows how to adjust a fingering mark so
3901 that it nestles close to the note head.
3903 @lilypond[quote,verbatim,relative=2]
3905 -\tweak self-alignment-X #0.5 % move horizontally left
3906 -\tweak Y-offset #ly:self-alignment-interface::y-aligned-on-self
3907 -\tweak self-alignment-Y #-1 % move vertically up
3912 @unnumberedsubsubsec Using the @code{aligned-on-parent} procedures
3914 @c Cannot document as they do not seem to operate consistently on all objects -td
3915 @c TODO investigate further
3917 The @code{aligned-on-parent} procedures are used in the same way
3918 as the @code{aligned-on-self} procedures, they difference being
3919 that they permit an object to be aligned with the @emph{edges} of
3920 the parent rather than the parent's reference point. The following
3921 example shows the difference:
3925 @lilypond[verbatim,quote]
3931 @unnumberedsubsubsec Using the @code{centered-on-parent} procedures
3933 @c Cannot document as they do not seem to operate consistently on all objects -td
3934 @c TODO investigate further
3938 @c TODO The align-interface, BassFigureAlignment and VerticalAlignment
3940 @node Using the break-alignable-interface
3941 @unnumberedsubsubsec Using the @code{break-alignable-interface}
3943 @cindex align to objects
3944 @cindex break-align-symbols
3946 Rehearsal marks and bar numbers may be aligned with notation
3947 objects other than bar lines. These objects include @code{ambitus},
3948 @code{breathing-sign}, @code{clef}, @code{custos}, @code{staff-bar},
3949 @code{left-edge}, @code{key-cancellation}, @code{key-signature}, and
3950 @code{time-signature}.
3952 Each type of object has its own default reference point, to which
3953 rehearsal marks are aligned:
3955 @lilypond[verbatim,quote,relative=1]
3956 % The rehearsal mark will be aligned to the right edge of the Clef
3957 \override Score.RehearsalMark.break-align-symbols = #'(clef)
3962 % The rehearsal mark will be aligned to the left edge of the Time Signature
3963 \override Score.RehearsalMark.break-align-symbols = #'(time-signature)
3969 % The rehearsal mark will be centered above the Breath Mark
3970 \override Score.RehearsalMark.break-align-symbols = #'(breathing-sign)
3979 A list of possible target alignment objects may be specified. If
3980 some of the objects are invisible at that point due to the setting
3981 of @code{break-visibility} or the explicit visibility settings for
3982 keys and clefs, the rehearsal mark or bar number is aligned to the
3983 first object in the list which is visible. If no objects in the
3984 list are visible the object is aligned to the bar line. If the bar
3985 line is invisible the object is aligned to the place where the bar
3988 @lilypond[verbatim,quote,relative=1]
3989 % The rehearsal mark will be aligned to the right edge of the Key Signature
3990 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
3995 % The rehearsal mark will be aligned to the right edge of the Clef
3996 \set Staff.explicitKeySignatureVisibility = #all-invisible
3997 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4002 % The rehearsal mark will be centered above the Bar Line
4003 \set Staff.explicitKeySignatureVisibility = #all-invisible
4004 \set Staff.explicitClefVisibility = #all-invisible
4005 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4012 The alignment of the rehearsal mark relative to the notation object
4013 can be changed, as shown in the following example. In a score with
4014 multiple staves, this setting should be done for all the staves.
4016 @lilypond[verbatim,quote,relative=1]
4017 % The RehearsalMark will be aligned with the right edge of the Key Signature
4018 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4024 % The RehearsalMark will be centered above the Key Signature
4025 \once \override Score.KeySignature.break-align-anchor-alignment = #CENTER
4029 % The RehearsalMark will be aligned with the left edge of the Key Signature
4030 \once \override Score.KeySignature.break-align-anchor-alignment = #LEFT
4036 The rehearsal mark can also be offset to the right or left of the left
4037 edge by an arbitrary amount. The units are staff-spaces:
4039 @lilypond[verbatim,quote,relative=1]
4040 % The RehearsalMark will be aligned with the left edge of the Key Signature
4041 % and then shifted right by 3.5 staff-spaces
4042 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4043 \once \override Score.KeySignature.break-align-anchor = #3.5
4047 % The RehearsalMark will be aligned with the left edge of the Key Signature
4048 % and then shifted left by 2 staff-spaces
4049 \once \override Score.KeySignature.break-align-anchor = #-2
4056 @node Vertical grouping of grobs
4057 @subsection Vertical grouping of grobs
4059 @c TODO Expand this section
4061 The VerticalAlignment and VerticalAxisGroup grobs work together.
4062 VerticalAxisGroup groups together different grobs like Staff, Lyrics,
4063 etc. VerticalAlignment then vertically aligns the different grobs
4064 grouped together by VerticalAxisGroup. There is usually only one
4065 VerticalAlignment per score but every Staff, Lyrics, etc. has its own
4069 @node Modifying stencils
4070 @subsection Modifying stencils
4072 All layout objects have a @code{stencil} property which is part of
4073 the @code{grob-interface}. By default, this property is usually
4074 set to a function specific to the object that is tailor-made to
4075 render the symbol which represents it in the output. For example,
4076 the standard setting for the @code{stencil} property of the
4077 @code{MultiMeasureRest} object is @code{ly:multi-measure-rest::print}.
4079 The standard symbol for any object can be replaced by modifying the
4080 @code{stencil} property to reference a different, specially-written,
4081 procedure. This requires a high level of knowledge of the internal
4082 workings of LilyPond, but there is an easier way which can often
4083 produce adequate results.
4085 This is to set the @code{stencil} property to the procedure which
4086 prints text -- @code{ly:text-interface::print} -- and to add a
4087 @code{text} property to the object which is set to contain the
4088 markup text which produces the required symbol. Due to the
4089 flexibility of markup, much can be achieved -- see in particular
4090 @ref{Graphic notation inside markup}.
4092 The following example demonstrates this by changing the note head
4093 symbol to a cross within a circle.
4095 @lilypond[verbatim,quote]
4097 \once \override NoteHead.stencil = #ly:text-interface::print
4098 \once \override NoteHead.text = \markup {
4100 \halign #-0.7 \draw-circle #0.85 #0.2 ##f
4101 \musicglyph #"noteheads.s2cross"
4109 Any of the glyphs in the feta Font can be supplied to the
4110 @code{\musicglyph} markup command -- see @ref{The Feta font}.
4112 @c TODO Add inserting eps files or ref to later
4114 @c TODO Add inserting Postscript or ref to later
4118 @ref{Graphic notation inside markup},
4119 @ref{Formatting text},
4120 @ref{Text markup commands},
4121 @ref{The Feta font}.
4124 @node Modifying shapes
4125 @subsection Modifying shapes
4128 * Modifying ties and slurs::
4131 @node Modifying ties and slurs
4132 @unnumberedsubsubsec Modifying ties and slurs
4134 @cindex slurs, modifying
4135 @cindex ties, modifying
4136 @cindex Bézier curves, control points
4137 @cindex control points, Bézier curves
4139 @code{Tie}s, @code{Slur}s, @code{PhrasingSlur}s,
4140 @code{LaissezVibrerTie}s and @code{RepeatTie}s are all drawn as
4141 third-order Bézier curves. If the shape of the tie or slur which
4142 is calculated automatically is not optimum, the shape may be
4143 modified manually in two ways:
4147 by specifying the displacements to be made to the control points
4148 of the automatically calculated Bézier curve, or
4151 by explicitly specifying the positions of the four control points
4152 required to define the wanted curve.
4155 Both methods are explained below. The first method is more suitable
4156 if only slight adjustments to the curve are required; the second may
4157 be better for creating curves which are related to just a single
4160 @subsubsubheading Cubic Bézier curves
4162 Third-order or cubic Bézier curves are defined by four control
4163 points. The first and fourth control points are precisely the
4164 starting and ending points of the curve. The intermediate two
4165 control points define the shape. Animations showing how the curve
4166 is drawn can be found on the web, but the following description
4167 may be helpful. The curve starts from the first control point
4168 heading directly towards the second, gradually bending over to
4169 head towards the third and continuing to bend over to head towards
4170 the fourth, arriving there travelling directly from the third
4171 control point. The curve is entirely contained in the
4172 quadrilateral defined by the four control points. Translations,
4173 rotations and scaling of the control points all result in exactly
4174 the same operations on the curve.
4176 @subsubsubheading Specifying displacements from current control points
4178 @cindex shaping slurs and ties
4181 In this example the automatic placement of the tie is not optimum,
4182 and @code{\tieDown} would not help.
4184 @lilypond[verbatim,quote,relative=1]
4188 { r4 <g c,> <g c,> <g c,> }
4192 Adjusting the control points of the tie with @code{\shape} allows
4193 the collisions to be avoided.
4195 The syntax of @code{\shape} is
4198 [-]@code{\shape} @var{displacements} @var{item}
4201 This will reposition the control-points of @var{item} by the amounts
4202 given by @var{displacements}. The @var{displacements} argument is a
4203 list of number pairs or a list of such lists. Each element of a pair
4204 represents the displacement of one of the coordinates of a
4205 control-point. If @var{item} is a string, the result is
4206 @code{\once\override} for the specified grob type. If @var{item} is
4207 a music expression, the result is the same music expression with an
4208 appropriate tweak applied.
4210 In other words, the @code{\shape} function can act as either a
4211 @code{\once\override} command or a @code{\tweak} command depending
4212 on whether the @var{item} argument is a grob name, like @qq{Slur},
4213 or a music expression, like @qq{(}. The @var{displacements} argument
4214 specifies the displacements of the four control points as a list of
4215 four pairs of (dx . dy) values in units of staff-spaces (or a list
4216 of such lists if the curve has more than one segment).
4218 The leading hyphen is required if and only if the @code{\tweak} form
4221 So, using the same example as above and the @code{\once\override}
4222 form of @code{\shape}, this will raise the tie by half a staff-space:
4224 @lilypond[verbatim,quote,relative=1]
4227 \shape #'((0 . 0.5) (0 . 0.5) (0 . 0.5) (0 . 0.5)) Tie
4231 { r4 <g c,> <g c,> <g c,> }
4235 This positioning of the tie is better, but maybe it should be raised
4236 more in the center. The following example does this, this time using
4237 the alternative @code{\tweak} form:
4239 @lilypond[verbatim,quote,relative=1]
4242 e1-\shape #'((0 . 0.5) (0 . 1) (0 . 1) (0 . 0.5)) ~ e
4245 { r4 <g c,> <g c,> <g c,> }
4249 Changes to the horizontal positions of the control points may be made
4250 in the same way, and two different curves starting at the same
4251 musical moment may also be shaped:
4253 @lilypond[verbatim,quote,ragged-right,relative=2]
4255 \shape #'((0.7 . -0.4) (0.5 . -0.4) (0.3 . -0.3) (0 . -0.2)) Slur
4256 \shape #'((0 . 0) (0 . 0.5) (0 . 0.5) (0 . 0)) PhrasingSlur
4260 The @code{\shape} function can also displace the control points of
4261 curves which stretch across line breaks. Each piece of the broken
4262 curve can be given its own list of offsets. If changes to a
4263 particular segment are not needed, the empty list can serve as a
4264 placeholder. In this example the line break makes the single slur
4267 @lilypond[verbatim,quote,ragged-right,relative=1]
4273 Changing the shapes of the two halves of the slur makes it clearer
4274 that the slur continues over the line break:
4276 @lilypond[verbatim,quote,ragged-right,relative=1]
4277 % () may be used as a shorthand for ((0 . 0) (0 . 0) (0 . 0) (0 . 0))
4278 % if any of the segments does not need to be changed
4280 (( 0 . 0) (0 . 0) (0 . 0) (0 . 1))
4281 ((0.5 . 1.5) (1 . 0) (0 . 0) (0 . -1.5))
4288 If an S-shaped curve is required the control points must always be
4289 adjusted manually --- LilyPond will never select such shapes
4292 @lilypond[verbatim,quote,relative=2]
4293 c8( e b-> f d' a e-> g)
4294 \shape #'((0 . -1) (5.5 . -0.5) (-5.5 . -10.5) (0 . -5.5)) PhrasingSlur
4295 c8\( e b-> f d' a e-> g\)
4298 @subsubsubheading Specifying control points explicitly
4300 The coordinates of the Bézier control points are specified in units
4301 of staff-spaces. The X@tie{}coordinate is relative to the reference
4302 point of the note to which the tie or slur is attached, and the
4303 Y@tie{}coordinate is relative to the staff center line. The
4304 coordinates are specified as a list of four pairs of decimal numbers
4305 (reals). One approach is to estimate the coordinates of the two
4306 end points, and then guess the two intermediate points. The optimum
4307 values are then found by trial and error. Be aware that these values
4308 may need to be manually adjusted if any further changes are made to
4309 the music or the layout.
4311 One situation where specifying the control points explicitly is
4312 preferable to specifying displacements is when they need to be
4313 specified relative to a single note. Here is an example of this.
4314 It shows one way of indicating a slur extending into alternative
4315 sections of a volta repeat.
4317 @lilypond[verbatim,quote,relative=2]
4319 \repeat volta 3 { c4 d( e f }
4324 % create a slur and move it to a new position
4325 % the <> is just an empty chord to carry the slur termination
4326 -\tweak control-points #'((-2 . 3.8) (-1 . 3.9) (0 . 4) (1 . 3.4)) ( <> )
4331 % create a slur and move it to a new position
4332 -\tweak control-points #'((-2 . 3) (-1 . 3.1) (0 . 3.2) (1 . 2.4)) ( <> )
4339 It is not possible to modify shapes of ties or slurs by changing
4340 the @code{control-points} property if there are multiple ties or slurs
4341 at the same musical moment -- the @code{\tweak} command will also not
4342 work in this case. However, the @code{tie-configuration} property of
4343 @code{TieColumn} can be overridden to set start line and direction as
4347 Internals Reference:
4348 @rinternals{TieColumn}.
4351 @node Modifying broken spanners
4352 @subsection Modifying broken spanners
4355 * Using alterBroken::
4358 @node Using alterBroken
4359 @unnumberedsubsubsec Using @code{\alterBroken}
4361 @cindex spanners, modifying
4362 @cindex broken spanners, modifying
4363 @funindex \alterBroken
4365 When a spanner crosses a line break or breaks, each piece
4366 inherits the attributes of the original spanner. Thus, ordinary
4367 tweaking of a broken spanner applies the same modifications to
4368 each of its segments. In the example below, overriding
4369 @code{thickness} affects the slur on either side of the line
4372 @lilypond[verbatim,quote,ragged-right,relative=2]
4374 \once\override Slur.thickness = 10
4380 Independently modifying the appearance of individual pieces
4381 of a broken spanner is possible with the @code{\alterBroken}
4382 command. This command can produce either an @code{\override}
4383 or a @code{\tweak} of a spanner property.
4385 The syntax for @code{\alterBroken} is
4388 [-]@code{\alterBroken} @var{property} @var{values} @var{item}
4391 The argument @var{values} is a list of values, one for each
4392 broken piece. If @var{item} is a grob name like @code{Slur} or
4393 @code{Staff.PianoPedalBracket}, the result is an @code{\override}
4394 of the specified grob type. If @var{item} is a music expression
4395 such as @qq{(} or @qq{[} the result is the same music expression
4396 with an appropriate tweak applied.
4398 The leading hyphen must be used with the @code{\tweak} form. Do
4399 not add it when @code{\alterBroken} is used as an
4402 In its @code{\override} usage, @code{\alterBroken} may be
4403 prefaced by @code{\once} or @code{\temporary} and reverted by
4404 using @code{\revert} with @var{property}.
4406 The following code applies an independent @code{\override} to
4407 each of the slur segments in the previous example:
4409 @lilypond[verbatim,quote,ragged-right,relative=2]
4411 \alterBroken thickness #'(10 1) Slur
4417 The @code{\alterBroken} command may be used with any spanner
4418 object, including @code{Tie}, @code{PhrasingSlur}, @code{Beam}
4419 and @code{TextSpanner}. For example, an editor preparing a
4420 scholarly edition may wish to indicate the absence of part of a
4421 phrasing slur in a source by dashing only the segment which has
4422 been added. The following example illustrates how this can be
4423 done, in this case using the @code{\tweak} form of the command:
4425 @lilypond[verbatim,quote,ragged-right,relative=2]
4426 % The empty list is conveniently used below, because it is the
4427 % default setting of dash-definition, resulting in a solid curve.
4428 c2-\alterBroken dash-definition #'(() ((0 1.0 0.4 0.75))) \(e
4433 It is important to understand that @code{\alterBroken} will set
4434 each piece of a broken spanner to the corresponding value in
4435 @var{values}. When there are fewer values than pieces, any
4436 additional piece will be assigned the empty list. This may lead
4437 to undesired results if the layout property is not set to the
4438 empty list by default. In such cases, each segment should be
4439 assigned an appropriate value.
4442 Line breaks may occur in different places following changes in
4443 layout. Settings chosen for @code{\alterBroken} may be unsuitable
4444 for a spanner that is no longer broken or is split into more
4445 segments than before. Explicit use of @code{\break} can guard
4446 against this situation.
4448 The @code{\alterBroken} command is ineffective for spanner
4449 properties accessed before line-breaking such as
4454 @rextend{Difficult tweaks}.
4457 @node Unpure-pure containers
4458 @subsection Unpure-pure containers
4460 @cindex Scheme, pure containers
4461 @cindex Scheme, unpure containers
4462 @cindex pure containers, Scheme
4463 @cindex unpure containers, Scheme
4464 @cindex horizontal spacing, overriding
4466 Unpure-pure containers are useful for overriding @emph{Y-axis} spacing
4467 calculations - specifically @code{Y-offset} and @code{Y-extent} - with a
4468 Scheme function instead of a literal (i.e. a number or pair).
4470 For certain grobs, the @code{Y-extent} is based on the @code{stencil}
4471 property, overriding the stencil property of one of these will
4472 require an additional @code{Y-extent} override with an unpure-pure
4473 container. When a function overrides a @code{Y-offset} and/or
4474 @code{Y-extent} it is assumed that this will trigger line breaking
4475 calculations too early during compilation. So the function is not
4476 evaluated at all (usually returning a value of @samp{0} or
4477 @samp{'(0 . 0)}) which can result in collisions. A @q{pure} function
4478 will not affect properties, objects or grob suicides and therefore will
4479 always have its Y-axis-related evaluated correctly.
4481 Currently, there are about thirty functions that are already considered
4482 @q{pure} and Unpure-pure containers are a way to set functions not on
4483 this list as @q{pure}. The @q{pure} function is evaluated @emph{before}
4484 any line-breaking and so the horizontal spacing can be adjusted
4485 @q{in time}. The @q{unpure} function is then evaluated @emph{after}
4488 @warning{As it is difficult to always know which functions are on this
4489 list we recommend that any @q{pure} functions you create do not use
4490 @code{Beam} or @code{VerticalAlignment} grobs.}
4492 An unpure-pure container is constructed as follows;
4494 @code{(ly:make-unpure-pure-container f0 f1)}
4496 where @code{f0} is a function taking @var{n} arguments (@var{n >= 1})
4497 and the first argument must always be the grob. This is the function
4498 that gives the actual result. @var{f1} is the function being labeled
4499 as @q{pure} that takes @var{n + 2} arguments. Again, the first argument
4500 must always still be the grob but the second and third are @q{start}
4501 and @q{end} arguments.
4503 @var{start} and @var{end} are, for all intents and purposes, dummy
4504 values that only matter for @code{Spanners} (i.e @code{Hairpin} or
4505 @code{Beam}), that can return different height estimations based on a
4506 starting and ending column.
4508 The rest are the other arguments to the first function (which
4509 may be none if @var{n = 1}).
4511 The results of the second function are used as an approximation of the
4512 value needed which is then used by the first function to get the real
4513 value which is then used for fine-tuning much later during the spacing
4516 @lilypond[verbatim,quote,ragged-right]
4517 #(define (square-line-circle-space grob)
4518 (let* ((pitch (ly:event-property (ly:grob-property grob 'cause) 'pitch))
4519 (notename (ly:pitch-notename pitch)))
4520 (if (= 0 (modulo notename 2))
4521 (make-circle-stencil 0.5 0.0 #t)
4522 (make-filled-box-stencil '(0 . 1.0)
4525 squareLineCircleSpace = {
4526 \override NoteHead.stencil = #square-line-circle-space
4529 smartSquareLineCircleSpace = {
4530 \squareLineCircleSpace
4531 \override NoteHead.Y-extent =
4532 #(ly:make-unpure-pure-container
4533 ly:grob::stencil-height
4534 (lambda (grob start end) (ly:grob::stencil-height grob)))
4537 \new Voice \with { \remove "Stem_engraver" }
4539 \squareLineCircleSpace
4541 \smartSquareLineCircleSpace
4546 In the first measure, without the unpure-pure container, the spacing
4547 engine does not know the width of the note head and lets it collide with
4548 the accidentals. In the second measure, with unpure-pure containers,
4549 the spacing engine knows the width of the note heads and avoids the
4550 collision by lengthening the line accordingly.
4552 Usually for simple calculations nearly-identical functions for both the
4553 @q{unpure} and @q{pure} parts can be used, by only changing the number
4554 of arguments passed to, and the scope of, the function.
4556 @warning{If a function is labeled as @q{pure} and it turns out not to
4557 be, the results can be unexpected.}
4560 @node Using music functions
4561 @section Using music functions
4563 @c TODO -- add @seealso, etc. to these subsections
4565 Where tweaks need to be reused with different music expressions,
4566 it is often convenient to make the tweak part of a @emph{music
4567 function}. In this section, we discuss only @emph{substitution}
4568 functions, where the object is to substitute a variable into a
4569 piece of LilyPond input code. Other more complex functions are
4570 described in @rextend{Music functions}.
4573 * Substitution function syntax::
4574 * Substitution function examples::
4577 @node Substitution function syntax
4578 @subsection Substitution function syntax
4580 Making a function that substitutes a variable into LilyPond
4581 code is easy. The general form of these functions is
4585 #(define-music-function
4586 (parser location @var{arg1} @var{arg2} @dots{})
4587 (@var{type1?} @var{type2?} @dots{})
4589 @var{@dots{}music@dots{}}
4596 @multitable @columnfractions .33 .66
4597 @item @code{@var{argN}}
4598 @tab @var{n}th argument
4600 @item @code{@var{typeN?}}
4601 @tab a scheme @emph{type predicate} for which @code{@var{argN}}
4602 must return @code{#t}.
4604 @item @code{@var{@dots{}music@dots{}}}
4605 @tab normal LilyPond input, using @code{$} (in places where only
4606 Lilypond constructs are allowed) or @code{#} (to use it as a Scheme
4607 value or music function argument or music inside of music lists) to
4612 The @code{parser} and @code{location} arguments are mandatory, and
4613 are used in some advanced situations as described in the
4614 @q{Extending} manual (see @rextend{Music functions}). For
4615 substitution functions, just be sure to include them.
4617 The list of type predicates is also required. Some of the most
4618 common type predicates used in music functions are:
4622 cheap-list? @emph{(use instead of }@q{list?}@emph{ for faster processing)}
4634 For a list of available type predicates, see
4635 @ref{Predefined type predicates}. User-defined type predicates
4640 @ref{Predefined type predicates}.
4643 @rextend{Music functions}.
4646 @file{lily/music-scheme.cc},
4648 @file{scm/lily.scm}.
4651 @node Substitution function examples
4652 @subsection Substitution function examples
4654 This section introduces some substitution function examples.
4655 These are not intended to be exhaustive, but rather to demonstrate
4656 some of the possibilities of simple substitution functions.
4658 In the first example, a function is defined that simplifies
4659 setting the padding of a TextScript:
4661 @lilypond[quote,verbatim,ragged-right]
4663 #(define-music-function
4664 (parser location padding)
4667 \once \override TextScript.padding = #padding
4671 c4^"piu mosso" b a b
4673 c4^"piu mosso" b a b
4675 c4^"piu mosso" b a b
4679 In addition to numbers, we can use music expressions such
4680 as notes for arguments to music functions:
4682 @lilypond[quote,verbatim,ragged-right]
4684 #(define-music-function
4685 (parser location note)
4688 \tweak NoteHead.stencil #ly:text-interface::print
4689 \tweak NoteHead.text
4690 \markup \musicglyph #"custodes.mensural.u0"
4691 \tweak Stem.stencil ##f
4695 \relative c' { c4 d e f \custosNote g }
4698 Substitution functions with multiple arguments can be defined:
4700 @lilypond[quote,verbatim,ragged-right]
4702 #(define-music-function
4703 (parser location padding tempotext)
4706 \once \override Score.MetronomeMark.padding = #padding
4707 \tempo \markup { \bold #tempotext }
4711 \tempo \markup { "Low tempo" }
4713 \tempoPadded #4.0 "High tempo"
4718 @c TODO: add appropriate @@ref's here.