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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 the notes are printed on one line.
219 @strong{@emph{TabStaff}}
221 Context for generating tablature. By default lays the music
222 expression out as a guitar tablature, printed on six lines.
224 @strong{@emph{DrumStaff}}
226 Handles typesetting for percussion. Can contain @code{DrumVoice}
228 @strong{@emph{VaticanaStaff}}
230 Same as @code{Staff}, except that it is designed for typesetting
231 a piece in gregorian style.
233 @strong{@emph{MensuralStaff}}
235 Same as @code{Staff}, except that it is designed for typesetting
236 a piece in mensural style.
238 @node Bottom-level contexts - voices
239 @unnumberedsubsubsec Bottom-level contexts - voices
241 Voice-level contexts initialise certain properties and start
242 appropriate engravers. A bottom-level context is one without
243 @code{defaultchild}. While it is possible to let it
244 accept/@/contain subcontexts, they can only be created and entered
247 @strong{@emph{Voice}}
249 Corresponds to a voice on a staff. This context handles the
250 conversion of dynamic signs, stems, beams, super- and sub-scripts,
251 slurs, ties, and rests. You have to instantiate this explicitly
252 if you require multiple voices on the same staff.
254 @strong{@emph{VaticanaVoice}}
256 Same as @code{Voice}, except that it is designed for typesetting
257 a piece in gregorian style.
259 @strong{@emph{MensuralVoice}}
261 Same as @code{Voice}, with modifications for typesetting a piece in
264 @strong{@emph{Lyrics}}
266 Corresponds to a voice with lyrics. Handles the printing of a
267 single line of lyrics.
269 @strong{@emph{DrumVoice}}
271 The voice context used in a percussion staff.
273 @strong{@emph{FiguredBass}}
275 The context in which @code{BassFigure} objects are created from
276 input entered in @code{\figuremode} mode.
278 @strong{@emph{TabVoice}}
280 The voice context used within a @code{TabStaff} context. Usually
281 left to be created implicitly.
283 @strong{@emph{CueVoice}}
285 A voice context used to render notes of a reduced size, intended
286 primarily for adding cue notes to a staff, see @ref{Formatting
287 cue notes}. Usually left to be created implicitly.
289 @strong{@emph{ChordNames}}
291 Typesets chord names.
296 Then the following, which I don't know what to do with:
298 * GregorianTranscriptionVoice
299 * GregorianTranscriptionStaff
302 Engraves fretboards from chords. Not easy... Not
304 There is now some documentation on FretBoards in the NR, under
305 instrument-specific notation -- cds.
310 Hard coded entry point for LilyPond. Cannot be tuned.
312 Silently discards all musical information given to this
317 @node Creating and referencing contexts
318 @subsection Creating and referencing contexts
323 @cindex referencing contexts
324 @cindex Contexts, creating and referencing
326 LilyPond will create lower-level contexts automatically if a music
327 expression is encountered before a suitable context exists, but this
328 is usually successful only for simple scores or music fragments like
329 the ones in the documentation. For more complex scores it is
330 advisable to specify all contexts explicitly with either the
331 @code{\new} or @code{\context} command. The syntax of
332 these two commands is very similar:
335 [\new | \context] @var{Context} [ = @var{name}] [@var{music-expression}]
339 where either @code{\new} or @code{\context} may be specified.
340 @var{Context} is the type of context which is to be created,
341 @var{name} is an optional name to be given to the particular context
342 being created and @var{music-expression} is a single music expression
343 that is to be interpreted by the engravers and performers in this
346 The @code{\new} prefix without a name is commonly used to create
347 scores with many staves:
349 @lilypond[quote,verbatim,relative=2]
352 % leave the Voice context to be created implicitly
362 and to place several voices into one staff:
364 @lilypond[quote,verbatim,relative=2]
380 @code{\new} should always be used to specify unnamed contexts.
382 The difference between @code{\new} and @code{\context} is in the
387 @code{\new} with or without a name will always create a fresh,
388 distinct, context, even if one with the same name already exists:
390 @lilypond[quote,verbatim,relative=2]
406 @code{\context} with a name specified will create a distinct context
407 only if a context of the same type with the same name in the same
408 context hierarchy does not already exist. Otherwise it will be taken
409 as a reference to that previously created context, and its music
410 expression will be passed to that context for interpretation.
412 One application of named contexts is in separating the score layout
413 from the musical content. Either of these two forms is valid:
415 @lilypond[quote,verbatim]
429 \context Voice = "one" {
434 \context Voice = "two" {
443 @lilypond[quote,verbatim]
448 \context Voice = "one" {
451 \context Voice = "two" {
457 \context Voice = "one" {
462 \context Voice = "two" {
472 Alternatively, variables may be employed to similar effect. See
473 @rlearning{Organizing pieces with variables}.
476 @code{\context} with no name will match the first of any previously
477 created contexts of the same type in the same context heirarchy,
478 even one that has been given a name, and its music expression will be
479 passed to that context for interpretation. This form is rarely
480 useful. However, @code{\context} with no name and no music expression
481 is used to set the context in which a Scheme procedure specified with
482 @code{\applyContext} is executed:
485 \new Staff \relative c' @{
488 \applyContext #(lambda (ctx)
490 (display (ly:context-current-moment ctx)))
497 A context must be named if it is to be referenced later, for example
498 when lyrics are associated with music:
501 \new Voice = "tenor" @var{music}
503 \new Lyrics \lyricsto "tenor" @var{lyrics}
507 For details of associating lyrics with music see
508 @ref{Automatic syllable durations}.
510 The properties of all contexts of a particular type can be modified
511 in a @code{\layout} block (with a different syntax), see
512 @ref{Changing all contexts of the same type}. This construct also
513 provides a means of keeping layout instructions separate from the
514 musical content. If a single context is to be modified, a @code{\with}
515 block must be used, see @ref{Changing just one specific context}.
519 @rlearning{Organizing pieces with variables}.
522 @ref{Changing just one specific context},
523 @ref{Automatic syllable durations}.
526 @node Keeping contexts alive
527 @subsection Keeping contexts alive
529 @cindex contexts, keeping alive
530 @cindex contexts, lifetime
532 Contexts are usually terminated at the first musical moment in
533 which they have nothing to do. So @code{Voice} contexts die as
534 soon as they contain no events; @code{Staff} contexts die as soon
535 as all the @code{Voice} contexts within them contain no events; etc.
536 This can cause difficulties if earlier contexts which have died
537 have to be referenced, for example, when changing staves with
538 @code{\change} commands, associating lyrics with a voice with
539 @code{\lyricsto} commands, or when adding further musical events to
542 There is an exception to this general rule: just one of the
543 @code{Voice} contexts in a @code{Staff} context or in a
544 @code{<<@dots{}>>} construct will always persist to the end of the
545 enclosing @code{Staff} context or @code{<<@dots{}>>} construct, even
546 though there may be periods when it has nothing to do. The context
547 to persist in this way will be the first one encountered in the
548 first enclosed @code{@{@dots{}@}} construct, ignoring any in enclosed
549 @code{<<@dots{}>>} constructs.
551 Any context can be kept alive by ensuring it has something to do at
552 every musical moment. @code{Staff} contexts are kept alive by
553 ensuring one of their voices is kept alive. One way of doing this
554 is to add spacer rests to a voice in parallel with the real music.
555 These need to be added to every @code{Voice} context which needs to
556 be kept alive. If several voices are to be used sporadically it is
557 safest to keep them all alive rather than attempting to rely on the
558 exceptions mentioned above.
560 In the following example, both voice A and voice B are kept alive
561 in this way for the duration of the piece:
563 @lilypond[quote,verbatim]
564 musicA = \relative c'' { d4 d d d }
565 musicB = \relative c'' { g4 g g g }
568 \new Voice = "A" { s1*5 } % Keep Voice "A" alive for 5 bars
569 \new Voice = "B" { s1*5 } % Keep Voice "B" alive for 5 bars
574 \context Voice = "A" {
578 \context Voice = "B" {
582 \context Voice = "A" { \musicA }
583 \context Voice = "B" { \musicB }
584 \context Voice = "A" { \musicA }
595 @cindex lyrics, aligning with sporadic melody
597 The following example shows how a sporadic melody line with lyrics
598 might be written using this approach. In a real situation the
599 melody and accompaniment would consist of several different
602 @lilypond[quote,verbatim]
603 melody = \relative c'' { a4 a a a }
604 accompaniment = \relative c' { d4 d d d }
605 words = \lyricmode { These words fol -- low the mel -- o -- dy }
608 \new Staff = "music" {
610 \new Voice = "melody" {
612 s1*4 % Keep Voice "melody" alive for 4 bars
615 \new Voice = "accompaniment" {
620 \context Voice = "melody" { \melody }
621 \context Voice = "accompaniment" { \accompaniment }
623 \context Voice = "accompaniment" { \accompaniment }
625 \context Voice = "melody" { \melody }
626 \context Voice = "accompaniment" { \accompaniment }
631 \new Lyrics \with { alignAboveContext = #"music" }
632 \lyricsto "melody" { \words }
637 An alternative way, which may be better in many circumstances, is
638 to keep the melody line alive by simply including spacer notes to
639 line it up correctly with the accompaniment:
641 @lilypond[quote,verbatim]
642 melody = \relative c'' {
648 accompaniment = \relative c' {
654 words = \lyricmode { These words fol -- low the mel -- o -- dy }
658 \new Staff = "music" {
660 \new Voice = "melody" {
664 \new Voice = "accompaniment" {
670 \new Lyrics \with { alignAboveContext = #"music" }
671 \lyricsto "melody" { \words }
677 @node Modifying context plug-ins
678 @subsection Modifying context plug-ins
680 @c TODO Should this be Modifying engravers or Modifying contexts?
682 Notation contexts (like @code{Score} and @code{Staff}) not only store
683 properties, they also contain plug-ins called @q{engravers} that create
684 notation elements. For example, the @code{Voice} context contains a
685 @code{Note_heads_engraver} and the @code{Staff} context contains a
688 For a full a description of each plug-in, see
690 @rinternals{Engravers and Performers}.
693 Internals Reference @expansion{} Translation @expansion{} Engravers.
695 Every context described in
697 @rinternals{Contexts}
700 Internals Reference @expansion{} Translation @expansion{} Context.
702 lists the engravers used for that context.
705 It can be useful to shuffle around these plug-ins. This is done by
706 starting a new context with @code{\new} or @code{\context}, and
712 \new @var{context} \with @{
720 @emph{@dots{}music@dots{}}
725 where the @dots{} should be the name of an engraver. Here is a simple
726 example which removes @code{Time_signature_engraver} and
727 @code{Clef_engraver} from a @code{Staff} context,
729 @lilypond[quote,relative=1,verbatim]
735 \remove "Time_signature_engraver"
736 \remove "Clef_engraver"
743 In the second staff there are no time signature or clef symbols. This
744 is a rather crude method of making objects disappear since it will affect
745 the entire staff. This method also influences the spacing, which may or
746 may not be desirable. More sophisticated methods of blanking objects
747 are shown in @rlearning{Visibility and color of objects}.
749 The next example shows a practical application. Bar lines and time
750 signatures are normally synchronized across the score. This is done
751 by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
752 This plug-in keeps an administration of time signature, location
753 within the measure, etc. By moving these engraver from @code{Score} to
754 @code{Staff} context, we can have a score where each staff has its own
757 @cindex polymetric scores
758 @cindex Time signatures, multiple
760 @lilypond[quote,verbatim]
764 \consists "Timing_translator"
765 \consists "Default_bar_line_engraver"
772 \consists "Timing_translator"
773 \consists "Default_bar_line_engraver"
783 \remove "Timing_translator"
784 \remove "Default_bar_line_engraver"
792 The order in which the engravers are specified is the order in
793 which they are called to carry out their processing. Usually the
794 order in which the engravers are specified does not matter, but in
795 a few special cases the order is important, for example where one
796 engraver writes a property and another reads it, or where one
797 engraver creates a grob and another must process it.
799 The following orderings are important:
803 the @code{Bar_engraver} must normally be first,
806 the @code{New_fingering_engraver} must come before the
807 @code{Script_column_engraver},
810 the @code{Timing_translator} must come before the
811 @code{Bar_number_engraver}.
817 @file{ly/engraver-init.ly}.
820 @node Changing context default settings
821 @subsection Changing context default settings
823 @cindex default context properties, changing
824 @cindex context properties, changing defaults
826 Context and grob properties can be changed with @code{\set}
827 and @code{\override} commands, as described in
828 @ref{Modifying properties}. These commands create music events,
829 making the changes take effect at the point in time the music
832 In contrast, this section explains how to change the @emph{default}
833 values of context and grob properties at the time the context is
834 created. There are two ways of doing this. One modifies the default
835 values in all contexts of a particular type, the other modifies the
836 default values in just one particular instance of a context.
839 * Changing all contexts of the same type::
840 * Changing just one specific context::
841 * Order of precedence::
844 @node Changing all contexts of the same type
845 @unnumberedsubsubsec Changing all contexts of the same type
847 @cindex \context in \layout block
851 The default context settings which are to be used for typesetting in
852 @code{Score}, @code{Staff}, @code{Voice} and other contexts may be
853 specified in a @code{\context} block within any @code{\layout}
856 Settings for Midi output as opposed to typesetting will have to be
857 separately specified in @code{\midi} blocks (see @ref{Output
858 definitions - blueprints for contexts}).
860 The @code{\layout} block should be placed within the @code{\score}
861 block to which it is to apply, after the music.
867 [context settings for all Voice contexts]
871 [context settings for all Staff contexts]
876 The following types of settings may be specified:
880 An @code{\override} command, but with the context name omitted
882 @lilypond[quote,verbatim]
885 a4^"Thicker stems" a a a
891 \override Stem.thickness = #4.0
898 Directly setting a context property
900 @lilypond[quote,verbatim]
903 a4^"Smaller font" a a a
916 A predefined command such as @code{\dynamicUp} or a music
917 expression like @code{\accidentalStyle dodecaphonic}
919 @lilypond[quote,verbatim]
922 a4^"Dynamics above" a a a
932 \accidentalStyle dodecaphonic
939 A user-defined variable containing a @code{\with} block; for details
940 of the @code{\with} block see
941 @ref{Changing just one specific context}.
943 @lilypond[quote,verbatim]
944 StaffDefaults = \with {
951 a4^"Smaller font" a a a
966 Property-setting commands can be placed in a @code{\layout} block
967 without being enclosed in a @code{\context} block. Such settings
968 are equivalent to including the same property-setting commands at
969 the start of every context of the type specified. If no context
970 is specified @emph{every} bottom-level context is affected, see
971 @ref{Bottom-level contexts - voices}. The syntax of a
972 property-setting command in a @code{\layout} block is the same as
973 the same command written in the music stream.
975 @lilypond[quote,verbatim]
979 a4^"Smaller font" a a a
984 \accidentalStyle dodecaphonic
986 \override Voice.Stem.thickness = #4.0
992 @node Changing just one specific context
993 @unnumberedsubsubsec Changing just one specific context
998 The context properties of just one specific context instance can be
999 changed in a @code{\with} block. All other context instances of the
1000 same type retain the default settings built into LilyPond and modified
1001 by any @code{\layout} block within scope. The @code{\with} block
1002 must be placed immediately after the @code{\new} @var{context-type}
1006 \new Staff \with @{ [context settings for this context instance only] @}
1012 Since such a @q{context modification} is specified inside of
1013 music, it will affect @emph{all} outputs (typesetting @emph{and}
1014 Midi) as opposed to changes within an output definition.
1016 The following types of settings may be specified:
1020 An @code{\override} command, but with the context name omitted
1022 @lilypond[quote,verbatim]
1025 \new Voice \with { \override Stem.thickness = #4.0 }
1028 a4^"Thick stems" a a a
1037 Directly setting a context property
1039 @lilypond[quote,verbatim]
1044 a4^"Default font" a a a
1048 \new Staff \with { fontSize = #-4 }
1051 a4^"Smaller font" a a a
1060 A predefined command such as @code{\dynamicUp}
1062 @lilypond[quote,verbatim]
1068 a4^"Dynamics below" a a a
1073 \new Staff \with { \accidentalStyle dodecaphonic }
1075 \new Voice \with { \dynamicUp }
1078 a4^"Dynamics above" a a a
1089 @node Order of precedence
1090 @unnumberedsubsubsec Order of precedence
1092 The value of a property which applies at a particular time is
1093 determined as follows:
1097 if an @code{\override} or @code{\set} command in the input stream is
1098 in effect that value is used,
1101 otherwise the default value taken from a @code{\with} statement
1102 on the context initiation statement is used,
1105 otherwise the default value taken from the most recent appropriate
1106 @code{\context} block in the @code{\layout} or @code{\midi} blocks
1110 otherwise the LilyPond built-in default is used.
1115 @rlearning{Modifying context properties}.
1118 @ref{Contexts explained},
1119 @ref{Bottom-level contexts - voices},
1120 @ref{The set command},
1121 @ref{The override command},
1122 @ref{The layout block,,The @code{@bs{}layout} block}.
1125 @node Defining new contexts
1126 @subsection Defining new contexts
1128 @cindex contexts, defining new
1129 @cindex engravers, including in contexts
1144 Specific contexts, like @code{Staff} and @code{Voice}, are made from
1145 simple building blocks. It is possible to create new types of
1146 contexts with different combinations of engraver plug-ins.
1148 The next example shows how to build a different type of
1149 @code{Voice} context from scratch. It will be similar to
1150 @code{Voice}, but only prints centered slash note heads. It can be used
1151 to indicate improvisation in jazz pieces,
1153 @lilypond[quote,ragged-right]
1154 \layout { \context {
1156 \type "Engraver_group"
1157 \consists "Note_heads_engraver"
1158 \consists "Rhythmic_column_engraver"
1159 \consists "Text_engraver"
1160 \consists "Pitch_squash_engraver"
1161 squashedPosition = #0
1162 \override NoteHead.style = #'slash
1167 \accepts "ImproVoice"
1171 a4 d8 bes8 \new ImproVoice { c4^"ad lib" c
1172 c4 c^"undress" c_"while playing :)" c }
1178 These settings are defined within a @code{\context} block inside a
1179 @code{\layout} block,
1189 In the following discussion, the example input shown should go in place
1190 of the @dots{} in the previous fragment.
1192 First it is necessary to define a name for the new context:
1198 Since it is similar to the @code{Voice} context, we want commands that
1199 work in (existing) @code{Voice} contexts to continue working. This is
1200 achieved by giving the new context an alias of @code{Voice},
1206 The context will print notes and instructive texts, so we need to add
1207 the engravers which provide this functionality, plus the engraver which
1208 groups notes, stems and rests which occur at the same musical moment
1212 \consists "Note_heads_engraver"
1213 \consists "Text_engraver"
1214 \consists "Rhythmic_column_engraver"
1217 The note heads should all be placed on the center line,
1220 \consists "Pitch_squash_engraver"
1221 squashedPosition = #0
1224 The @code{Pitch_squash_engraver} modifies note heads (created
1225 by the @code{Note_heads_engraver}) and sets their vertical
1226 position to the value of @code{squashedPosition}, in this
1227 case@tie{}@code{0}, the center line.
1229 The notes look like a slash, and have no stem,
1232 \override NoteHead.style = #'slash
1236 All these plug-ins have to communicate under the control of the
1237 context. The mechanisms with which contexts communicate are
1238 established by declaring the context @code{\type}. Within a
1239 @code{\layout} block, most contexts will be of type
1240 @code{Engraver_group}. Some special contexts and contexts in
1241 @code{\midi} blocks use other context types. Copying and
1242 modifying an existing context definition will also fill in the
1243 type. Since this example creates a definition from scratch, it
1244 needs to be specified explicitly.
1247 \type "Engraver_group"
1250 Put together, we get
1255 \type "Engraver_group"
1256 \consists "Note_heads_engraver"
1257 \consists "Text_engraver"
1258 \consists "Rhythmic_column_engraver"
1259 \consists "Pitch_squash_engraver"
1260 squashedPosition = #0
1261 \override NoteHead.style = #'slash
1268 Contexts form hierarchies. We want to place the @code{ImproVoice}
1269 context within the @code{Staff} context, just like normal @code{Voice}
1270 contexts. Therefore, we modify the @code{Staff} definition with the
1271 @code{\accepts} command,
1281 The opposite of @code{\accepts} is @code{\denies},
1282 which is sometimes needed when reusing existing context definitions.
1284 Putting both into a @code{\layout} block, like
1294 \accepts "ImproVoice"
1299 Then the output at the start of this subsection can be entered as
1307 c c_"while playing :)"
1313 To complete this example, changes affecting the context hierarchy
1314 should be repeated in a @code{\midi} block so that Midi output
1315 depends on the same context relations.
1319 Internals Reference:
1320 @rinternals{Engraver_group},
1321 @rinternals{Note_heads_engraver},
1322 @rinternals{Text_engraver},
1323 @rinternals{Rhythmic_column_engraver},
1324 @rinternals{Pitch_squash_engraver}.
1327 @node Context layout order
1328 @subsection Context layout order
1330 @cindex contexts, layout order
1334 Contexts are normally positioned in a system from top to bottom
1335 in the order in which they are encountered in the input file. When
1336 contexts are nested, the outer context will include inner nested
1337 contexts as specified in the input file, provided the inner contexts
1338 are included in the outer context's @qq{accepts} list. Nested
1339 contexts which are not included in the outer context's @qq{accepts}
1340 list will be repositioned below the outer context rather than nested
1343 The @qq{accepts} list of a context can be changed with the
1344 @code{\accepts} and @code{\denies} commands. @code{\accepts} adds a
1345 context to the @qq{accepts} list and @code{\denies} removes a context
1346 from the list. For example, it would not normally be desirable for
1347 chord names to be nested within a @code{Staff} context, so the
1348 @code{ChordNames} context is not included by default in the @qq{accepts}
1349 list of the @code{Staff} context, but if this were to be required it can
1352 @lilypond[verbatim,quote]
1356 \chords { d1:m7 b1:min7.5- }
1361 @lilypond[verbatim,quote]
1365 \chords { d1:m7 b1:min7.5- }
1370 \accepts "ChordNames"
1376 @code{\denies} is mainly used when a new context is being based on
1377 another, but the required nesting differs. For example, the
1378 @code{VaticanaStaff} context is based on the @code{Staff} context, but
1379 with the @code{VaticanaVoice} context substituted for the @code{Voice}
1380 context in the @qq{accepts} list.
1382 @cindex contexts, implicit
1383 @cindex implicit contexts
1384 @funindex \defaultchild
1386 Note that a context will be silently created implicitly if a
1387 command is encountered when there is no suitable context available
1390 Within a context definition, the type of subcontext to be
1391 implicitly created is specified using @code{\defaultchild}. A
1392 number of music events require a @samp{Bottom} context: when such
1393 an event is encountered, subcontexts are created recursively until
1394 reaching a context with no @samp{defaultchild} setting.
1396 Implicit context creation can at times give rise to unexpected new
1397 staves or scores. Using @code{\new} to create contexts explicitly
1398 avoids those problems.
1400 @cindex alignAboveContext
1401 @cindex alignBelowContext
1402 @funindex alignAboveContext
1403 @funindex alignBelowContext
1405 Sometimes a context is required to exist for just a brief period, a
1406 good example being the staff context for an ossia. This is usually
1407 achieved by introducing the context definition at the appropriate
1408 place in parallel with corresponding section of the main music.
1409 By default, the temporary context will be placed below all the
1410 existing contexts. To reposition it above the context called
1411 @qq{main}, it should be defined like this:
1414 @code{\new Staff \with @{ alignAboveContext = #"main" @} }
1417 A similar situation arises when positioning a temporary lyrics
1418 context within a multi-staved layout such as a @code{ChoirStaff},
1419 for example, when adding a second verse to a repeated section.
1420 By default the temporary lyrics context will be placed beneath the
1421 lower staves. By defining the temporary lyrics context with
1422 @code{alignBelowContext} it can be positioned correctly beneath
1423 the (named) lyrics context containing the first verse.
1425 Examples showing this repositioning of temporary contexts can be
1426 found elsewhere --- see @rlearning{Nesting music expressions},
1427 @ref{Modifying single staves} and @ref{Techniques specific to lyrics}.
1431 @rlearning{Nesting music expressions}.
1434 @ref{Modifying single staves},
1435 @ref{Techniques specific to lyrics}.
1438 @rprogram{An extra staff appears}.
1441 @file{ly/engraver-init.ly}.
1444 @node Explaining the Internals Reference
1445 @section Explaining the Internals Reference
1448 * Navigating the program reference::
1449 * Layout interfaces::
1450 * Determining the grob property::
1451 * Naming conventions::
1454 @node Navigating the program reference
1455 @subsection Navigating the program reference
1457 @c TODO remove this (it's in the LM)
1458 @c Replace with more factual directions
1460 Suppose we want to move the fingering indication in the fragment
1463 @lilypond[quote,relative=2,verbatim]
1469 If you visit the documentation on fingering instructions (in
1470 @ref{Fingering instructions}), you will notice:
1475 Internals Reference: @rinternals{Fingering}.
1480 @c outdated info; probably will delete.
1482 This fragment points to two parts of the program reference: a page
1483 on @code{FingeringEvent} and one on @code{Fingering}.
1485 The page on @code{FingeringEvent} describes the properties of the music
1486 expression for the input @w{@code{-2}}. The page contains many links
1487 forward. For example, it says
1490 Accepted by: @rinternals{Fingering_engraver},
1494 That link brings us to the documentation for the Engraver, the
1498 This engraver creates the following layout objects: @rinternals{Fingering}.
1501 In other words, once the @code{FingeringEvent}s are interpreted, the
1502 @code{Fingering_engraver} plug-in will process them.
1506 @c I can't figure out what this is supposed to mean. -gp
1508 The @code{Fingering_engraver} is also listed to create
1509 @rinternals{Fingering} objects,
1511 @c old info? it doesn't make any sense to me with our current docs.
1513 second bit of information listed under @b{See also} in the Notation
1518 The programmer's reference is available as an HTML document. It is
1519 highly recommended that you read it in HTML form, either online or
1520 by downloading the HTML documentation. This section will be much more
1521 difficult to understand if you are using the
1525 Follow the link to @rinternals{Fingering}. At the top of the
1529 Fingering objects are created by: @rinternals{Fingering_engraver} and
1530 @rinternals{New_fingering_engraver}.
1533 By following related links inside the program reference, we can follow the
1534 flow of information within the program:
1538 @item @rinternals{Fingering}:
1539 @rinternals{Fingering} objects are created by:
1540 @rinternals{Fingering_engraver}
1542 @item @rinternals{Fingering_engraver}:
1543 Music types accepted: @rinternals{fingering-event}
1545 @item @rinternals{fingering-event}:
1546 Music event type @code{fingering-event} is in Music expressions named
1547 @rinternals{FingeringEvent}
1550 This path goes against the flow of information in the program: it
1551 starts from the output, and ends at the input event. You could
1552 also start at an input event, and read with the flow of
1553 information, eventually ending up at the output object(s).
1555 The program reference can also be browsed like a normal document. It
1556 contains chapters on
1558 @rinternals{Music definitions},
1561 @code{Music definitions}
1563 on @rinternals{Translation}, and the @rinternals{Backend}. Every
1564 chapter lists all the definitions used and all properties that may be
1568 @node Layout interfaces
1569 @subsection Layout interfaces
1571 @cindex interface, layout
1572 @cindex layout interface
1575 The HTML page that we found in the previous section describes the
1576 layout object called @rinternals{Fingering}. Such an object is a
1577 symbol within the score. It has properties that store numbers (like
1578 thicknesses and directions), but also pointers to related objects. A
1579 layout object is also called a @emph{Grob}, which is short for Graphical
1580 Object. For more details about Grobs, see @rinternals{grob-interface}.
1582 The page for @code{Fingering} lists the definitions for the
1583 @code{Fingering} object. For example, the page says
1586 @code{padding} (dimension, in staff space):
1592 which means that the number will be kept at a distance of at least 0.5
1596 Each layout object may have several functions as a notational or
1597 typographical element. For example, the Fingering object
1598 has the following aspects
1602 Its size is independent of the horizontal spacing, unlike slurs or beams.
1605 It is a piece of text. Granted, it is usually a very short text.
1608 That piece of text is typeset with a font, unlike slurs or beams.
1611 Horizontally, the center of the symbol should be aligned to the
1612 center of the note head.
1615 Vertically, the symbol is placed next to the note and the staff.
1618 The vertical position is also coordinated with other superscript
1619 and subscript symbols.
1622 Each of these aspects is captured in so-called @emph{interface}s,
1623 which are listed on the @rinternals{Fingering} page at the bottom
1626 This object supports the following interfaces:
1627 @rinternals{item-interface},
1628 @rinternals{self-alignment-interface},
1629 @rinternals{side-position-interface}, @rinternals{text-interface},
1630 @rinternals{text-script-interface}, @rinternals{font-interface},
1631 @rinternals{finger-interface}, and @rinternals{grob-interface}.
1634 Clicking any of the links will take you to the page of the respective
1635 object interface. Each interface has a number of properties. Some of
1636 them are not user-serviceable (@q{Internal properties}), but others
1639 We have been talking of @emph{the} @code{Fingering} object, but actually it
1640 does not amount to much. The initialization file (see
1641 @rlearning{Other sources of information})
1642 @file{scm/define-grobs.scm} shows the soul of the @q{object},
1647 (avoid-slur . around)
1648 (slur-padding . 0.2)
1649 (staff-padding . 0.5)
1650 (self-alignment-X . 0)
1651 (self-alignment-Y . 0)
1652 (script-priority . 100)
1653 (stencil . ,ly:text-interface::print)
1654 (direction . ,ly:script-interface::calc-direction)
1655 (font-encoding . fetaText)
1656 (font-size . -5) ; don't overlap when next to heads.
1657 (meta . ((class . Item)
1658 (interfaces . (finger-interface
1660 text-script-interface
1662 side-position-interface
1663 self-alignment-interface
1664 item-interface))))))
1668 As you can see, the @code{Fingering} object is nothing more than a
1669 bunch of variable settings, and the webpage in the Internals Reference
1670 is directly generated from this definition.
1673 @node Determining the grob property
1674 @subsection Determining the grob property
1676 @c TODO remove this (it's in the LM)
1677 @c Replace with more factual directions
1679 Recall that we wanted to change the position of the @b{2} in
1681 @lilypond[quote,relative=2,verbatim]
1687 Since the @b{2} is vertically positioned next to its note, we have to
1688 meddle with the interface associated with this positioning. This is
1689 done using @code{side-position-interface}. The page for this interface
1693 @code{side-position-interface}
1695 Position a victim object (this one) next to other objects (the
1696 support). The property @code{direction} signifies where to put the
1697 victim object relative to the support (left or right, up or down?)
1702 Below this description, the variable @code{padding} is described as
1707 (dimension, in staff space)
1709 Add this much extra space between objects that are next to each other.
1713 By increasing the value of @code{padding}, we can move the
1714 fingering away from the note head. The following command inserts
1715 3 staff spaces of white
1716 between the note and the fingering:
1718 \once \override Voice.Fingering.padding = #3
1721 Inserting this command before the Fingering object is created,
1722 i.e., before @code{c2}, yields the following result:
1724 @lilypond[quote,relative=2,verbatim]
1725 \once \override Voice.Fingering.padding = #3
1732 In this case, the context for this tweak is @code{Voice}. This
1733 fact can also be deduced from the program reference, for the page for
1734 the @rinternals{Fingering_engraver} plug-in says
1737 Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
1741 @node Naming conventions
1742 @subsection Naming conventions
1744 Another thing that is needed, is an overview of the various naming
1748 @item scheme functions: lowercase-with-hyphens (incl. one-word
1750 @item scheme functions: ly:plus-scheme-style
1751 @item music events, music classes and music properties:
1753 @item Grob interfaces: scheme-style
1754 @item backend properties: scheme-style (but X and Y!)
1755 @item contexts (and MusicExpressions and grobs): Capitalized or
1757 @item context properties: lowercaseFollowedByCamelCase
1759 Capitalized_followed_by_lowercase_and_with_underscores
1762 Questions to be answered:
1764 @item Which of these are conventions and which are rules?
1765 @item Which are rules of the underlying language, and which are
1769 @node Modifying properties
1770 @section Modifying properties
1772 @c TODO change the menu and subsection node names to use
1773 @c backslash once the new macro to handle the refs
1774 @c is available. Need to find and change all refs at
1775 @c the same time. -td
1778 * Overview of modifying properties::
1780 * The override command::
1781 * The tweak command::
1782 * set versus override::
1783 * Modifying alists::
1787 @node Overview of modifying properties
1788 @subsection Overview of modifying properties
1790 Each context is responsible for creating certain types of graphical
1791 objects. The settings used for printing these objects are also stored by
1792 context. By changing these settings, the appearance of objects can be
1795 There are two different kinds of properties stored in contexts:
1796 context properties and grob properties. Context properties are
1797 properties that apply to the context as a whole and control
1798 how the context itself is displayed. In contrast, grob properties
1799 apply to specific grob types that will be displayed in the context.
1801 The @code{\set} and @code{\unset} commands are used to change values
1802 for context properties. The @code{\override} and @code{\revert}
1803 commands are used to change values for grob properties.
1806 The syntax for this is
1809 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1812 Here @var{name} is the name of a graphical object, like
1813 @code{Stem} or @code{NoteHead}, and @var{property} is an internal
1814 variable of the formatting system (@q{grob property} or @q{layout
1815 property}). The latter is a symbol, so it must be quoted. The
1816 subsection @ref{Modifying properties}, explains what to fill in
1817 for @var{name}, @var{property}, and @var{value}. Here we only
1818 discuss the functionality of this command.
1823 \override Staff.Stem.thickness = #4.0
1827 makes stems thicker (the default is 1.3, with staff line thickness as a
1828 unit). Since the command specifies @code{Staff} as context, it only
1829 applies to the current staff. Other staves will keep their normal
1830 appearance. Here we see the command in action:
1832 @lilypond[quote,verbatim,relative=2]
1834 \override Staff.Stem.thickness = #4.0
1840 The @code{\override} command changes the definition of the @code{Stem}
1841 within the current @code{Staff}. After the command is interpreted
1842 all stems are thickened.
1844 Analogous to @code{\set}, the @var{context} argument may be left out,
1845 causing the default context @code{Voice} to be used. Adding
1846 @code{\once} applies the change during one timestep only.
1848 @lilypond[quote,verbatim,relative=2]
1850 \once \override Stem.thickness = #4.0
1855 The @code{\override} must be done before the object is
1856 started. Therefore, when altering @emph{Spanner} objects such as slurs
1857 or beams, the @code{\override} command must be executed at the moment
1858 when the object is created. In this example,
1860 @lilypond[quote,verbatim,relative=2]
1861 \override Slur.thickness = #3.0
1863 \override Beam.beam-thickness = #0.6
1868 the slur is fatter but the beam is not. This is because the command for
1869 @code{Beam} comes after the Beam is started, so it has no effect.
1871 Analogous to @code{\unset}, the @code{\revert} command for a context
1872 undoes an @code{\override} command; like with @code{\unset}, it only
1873 affects settings that were made in the same context. In other words, the
1874 @code{\revert} in the next example does not do anything.
1877 \override Voice.Stem.thickness = #4.0
1878 \revert Staff.Stem.thickness
1881 Some tweakable options are called @q{subproperties} and reside inside
1882 properties. To tweak those, use commands of the form
1884 @c leave this as a long long
1886 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
1893 \override Stem.details.beamed-lengths = #'(4 4 3)
1899 Internals Reference:
1900 @rinternals{Backend},
1901 @rinternals{All layout objects},
1902 @rinternals{OverrideProperty},
1903 @rinternals{RevertProperty},
1904 @rinternals{PropertySet}.
1907 The back-end is not very strict in type-checking object properties.
1908 Cyclic references in Scheme values for properties can cause hangs
1909 or crashes, or both.
1912 @node The set command
1913 @subsection The @code{@bs{}set} command
1917 @cindex changing properties
1919 Each context has a set of @emph{properties}, variables contained
1920 in that context. Context properties are changed with the @code{\set}
1921 command, which has the following syntax:
1924 \set @var{context}.@var{property} = #@var{value}
1927 @var{value} is a Scheme object, which is why it must be preceded by
1928 the @code{#}@tie{}character.
1930 Contexts properties are usually named in
1931 @code{studlyCaps}. They mostly control the translation from
1932 music to notation, e.g. @code{localKeySignature} (for determining
1933 whether to print accidentals), or @code{measurePosition} (for
1934 determining when to print a bar line). Context properties can
1935 change value over time while interpreting a piece of music;
1936 @code{measurePosition} is an obvious example of
1937 this. Context properties are modified with @code{\set}.
1939 For example, multimeasure rests will be combined into a single bar
1940 if the context property @code{skipBars} is set to @code{#t}:
1942 @lilypond[quote,verbatim,relative=2]
1944 \set Score.skipBars = ##t
1948 If the @var{context} argument is left out, then the property will be
1949 set in the current bottom context (typically @code{ChordNames},
1950 @code{Voice}, @code{TabVoice}, or @code{Lyrics}).
1952 @lilypond[quote,verbatim,relative=2]
1953 \set Score.autoBeaming = ##f
1957 \set autoBeaming = ##t
1965 The change is applied @q{on-the-fly}, during the music, so that the
1966 setting only affects the second group of eighth notes.
1968 Note that the bottom-most context does not always contain the property
1969 that you wish to change -- for example, attempting to set the
1970 @code{skipBars} property of the default bottom context, in this case
1971 @code{Voice}, will have no effect, because skipBars is a property of
1972 the @code{Score} context.
1974 @lilypond[quote,verbatim,relative=2]
1980 Contexts are hierarchical, so if an enclosing context was specified, for
1981 example @code{Staff}, then the change would also apply to all
1982 @code{Voice}s in the current staff.
1986 The @code{\unset} command:
1989 \unset @var{context}.@var{property}
1993 is used to remove the definition of @var{property} from
1994 @var{context}. This command removes
1995 the definition only if it is set in @var{context}.
1996 Properties that have been set in enclosing contexts will
1997 not be altered by an unset in an enclosed context:
1999 @lilypond[quote,verbatim,relative=2]
2000 \set Score.autoBeaming = ##t
2005 \unset Score.autoBeaming
2013 Like @code{\set}, the @var{context} argument does not have to be
2014 specified for a bottom context, so the two statements
2017 \set Voice.autoBeaming = ##t
2018 \set autoBeaming = ##t
2022 are equivalent if the current bottom context is @code{Voice}.
2026 Preceding a @code{\set} command by @code{\once} makes the
2027 setting apply to only a single time-step:
2029 @lilypond[quote,verbatim,relative=2]
2031 \once \set fontSize = #4.7
2036 A full description of all available context properties is in the
2037 internals reference, see
2039 @rinternals{Tunable context properties}.
2042 Translation @expansion{} Tunable context properties.
2046 Internals Reference:
2047 @rinternals{Tunable context properties}.
2050 @node The override command
2051 @subsection The @code{\override} command
2053 @cindex grob properties
2054 @cindex properties, grob
2057 There is a special type of context property: the grob
2058 description. Grob descriptions are named in @code{StudlyCaps}
2059 (starting with capital letters). They contain the
2060 @q{default settings} for a particular kind of grob as an
2061 association list. See @file{scm/define-grobs.scm}
2062 to see the settings for each grob description. Grob descriptions
2063 are modified with @code{\override}.
2065 The syntax for the @code{\override} command is
2068 \override [@var{context}.]@var{GrobName}.@var{property} = #@var{value}
2071 For example, we can increase the thickness of a note stem by
2072 overriding the @code{thickness} property of the @code{Stem}
2075 @lilypond[quote,verbatim,relative=2]
2077 \override Voice.Stem.thickness = #3.0
2081 If no context is specified in an @code{\override}, the bottom
2084 @lilypond[quote,verbatim,relative=2]
2085 { \override Staff.Stem.thickness = #3.0
2089 \override Stem.thickness = #0.5
2098 Some tweakable options are called @q{subproperties} and reside inside
2099 properties. To tweak those, use commands in the form
2102 \override Stem.details.beamed-lengths = #'(4 4 3)
2105 or to modify the ends of spanners, use a form like these
2108 \override TextSpanner.bound-details.left.text = #"left text"
2109 \override TextSpanner.bound-details.right.text = #"right text"
2113 @cindex reverting overrides
2114 @cindex overrides, reverting
2116 The effects of @code{\override} can be undone by @code{\revert}.
2118 The syntax for the @code{\revert} command is
2121 \revert [@var{context}.]@var{GrobName}.@var{property}
2126 @lilypond[quote,verbatim,relative=2]
2128 \override Voice.Stem.thickness = #3.0
2130 \revert Voice.Stem.thickness
2134 The effects of @code{\override} and @code{\revert} apply to all
2135 grobs in the affected context from the current time forward:
2137 @lilypond[quote,verbatim,relative=2]
2142 \override Staff.Stem.thickness = #3.0
2146 \revert Staff.Stem.thickness
2154 @cindex overriding for only one moment
2156 @code{\once} can be used with @code{\override}
2157 to affect only the current time step:
2159 @lilypond[quote,verbatim,relative=2]
2163 \override Stem.thickness = #3.0
2167 \once \override Stem.thickness = #3.0
2176 Commands which change output generally look like
2179 \override Voice.Stem.thickness = #3.0
2183 To construct this tweak we must determine these bits of information:
2186 @item the context: here @code{Voice}.
2187 @item the layout object: here @code{Stem}.
2188 @item the layout property: here @code{thickness}.
2189 @item a sensible value: here @code{3.0}.
2192 @cindex internal documentation
2193 @cindex finding graphical objects
2194 @cindex graphical object descriptions
2197 @cindex internal documentation
2199 For many properties, regardless of the data type of the property, setting the
2200 property to false (@code{#f}) will result in turning it off, causing
2201 LilyPond to ignore that property entirely. This is particularly useful for
2202 turning off grob properties which may otherwise be causing problems.
2204 We demonstrate how to glean this information from the notation manual
2205 and the program reference.
2209 Internals Reference:
2210 @rinternals{Backend}
2213 @node The tweak command
2214 @subsection The @code{\tweak} command
2219 Changing grob properties
2220 with @code{\override} causes the changes to apply to all of the
2221 given grobs in the context at the moment the change applies.
2222 Sometimes, however, it is desirable to have changes apply to just
2223 one grob, rather than to all grobs in the affected context. This is
2224 accomplished with the @code{\tweak} command, which has the following
2228 \tweak [@var{layout-object}.]@var{grob-property} @var{value}
2231 Specifying @var{layout-object} is optional.
2232 The @code{\tweak} command applies to the music object that immediately
2233 follows @var{value} in the music stream.
2236 In some cases, it is possible to take a short-cut for tuning
2237 graphical objects. For objects that are created directly from
2238 an item in the input file, you can use the @code{\tweak} command.
2241 @lilypond[relative=2,verbatim,quote]
2246 \tweak duration-log #1
2255 The main use of the @code{\tweak} command is to modify just
2256 one of a number of notation elements which start at the same musical
2257 moment, like the notes of a chord, or tuplet brackets which start
2260 The @code{\tweak} command sets a property in the following object
2261 directly, without requiring the grob name or context to be
2262 specified. For this to work, it is necessary for the @code{\tweak}
2263 command to remain immediately adjacent to the object to which it is
2264 to apply after the input file has been converted to a music stream.
2265 This is often not the case, as many additional elements are inserted
2266 into the music stream implicitly. For example, when a note which is
2267 not part of a chord is processed, LilyPond implicitly inserts a
2268 @code{ChordEvent} event before the note, so separating the tweak
2269 from the note. However, if chord symbols are placed round the
2270 tweak and the note, the @code{\tweak} command comes after the
2271 @code{ChordEvent} in the music stream, so remaining adjacent to the
2272 note, and able to modify it.
2276 @lilypond[relative=2,verbatim,quote]
2277 <\tweak color #red c>4
2283 @lilypond[relative=2,verbatim,quote]
2284 \tweak color #red c4
2289 For an introduction to the syntax and uses of the tweak command
2290 see @rlearning{Tweaking methods}.
2292 When several similar items are placed at the same musical moment,
2293 the @code{\override} command cannot be used to modify just one of
2294 them -- this is where the @code{\tweak} command must be used.
2295 Items which may appear more than once at the same musical moment
2296 include the following:
2298 @c TODO expand to include any further uses of \tweak
2300 @item note heads of notes inside a chord
2301 @item articulation signs on a single note
2302 @item ties between notes in a chord
2303 @item tuplet brackets starting at the same time
2306 @c TODO add examples of these
2308 @cindex chord, modifying one note in
2310 In this example, the color of one note head and the type of another
2311 note head are modified within a single chord:
2313 @lilypond[relative=2,verbatim,quote]
2318 \tweak duration-log #1
2323 @code{\tweak} can be used to modify slurs:
2325 @lilypond[verbatim,quote,relative=1]
2326 c-\tweak thickness #5 ( d e f)
2330 For the @code{\tweak} command to work, it must
2331 remain immediately adjacent to the object to which it is
2332 to apply after the input file has been converted to a music stream.
2333 Tweaking a whole chord does not do anything since its music event
2334 only acts as a container, and all layout objects are created from events
2335 inside of the @code{EventChord}:
2337 @lilypond[relative=2,verbatim,quote]
2338 \tweak color #red c4
2339 \tweak color #red <c e>4
2340 <\tweak color #red c e>4
2343 The simple @code{\tweak} command cannot be used to modify any object
2344 that is not directly created from the input. In particular
2345 it will not affect stems, automatic
2346 beams or accidentals, since these are generated later by
2347 @code{NoteHead} layout objects rather than by music elements in the
2350 Such indirectly created layout objects can be tweaked using the form
2351 of the @code{\tweak} command in which the grob name is specified
2354 @lilypond[relative=2,verbatim,quote]
2355 \tweak Stem.color #red
2356 \tweak Beam.color #green c8 e
2357 <c e \tweak Accidental.font-size #-3 ges>4
2360 @code{\tweak} cannot be used to modify clefs or time
2361 signatures, since these become separated from any preceding
2362 @code{\tweak} command in the input stream by the automatic
2363 insertion of extra elements required to specify the context.
2365 Several @code{\tweak} commands may be placed before a
2366 notational element -- all affect it:
2368 @lilypond[verbatim,quote,relative=1]
2370 -\tweak style #'dashed-line
2371 -\tweak dash-fraction #0.2
2372 -\tweak thickness #3
2378 The music stream which is generated from a section of an input file,
2379 including any automatically inserted elements, may be examined,
2380 see @rextend{Displaying music expressions}. This may be helpful in
2381 determining what may be modified by a @code{\tweak} command, or
2382 in determining how to adjust the input to make a @code{\tweak}
2387 @rlearning{Tweaking methods}.
2390 @rextend{Displaying music expressions}.
2394 @cindex tweaking control points
2395 @cindex control points, tweaking
2397 The @code{\tweak} command cannot be used to modify the control
2398 points of just one of several ties in a chord, other than the first
2399 one encountered in the input file.
2401 @node set versus override
2402 @subsection @code{\set} vs. @code{\override}
2404 @c TODO Should't a bunch of that be explained earlier?
2408 Both @code{\set} and @code{\override} manipulate properties
2409 associated with contexts. In either case, properties heed the
2410 hierarchy of contexts: properties not set in a context itself show
2411 the values of the respective parent context.
2413 Values and lifetime of context properties are dynamic and only
2414 available when music is being interpreted, @q{iterated}. At the
2415 time of context creation, properties are initialized from the
2416 corresponding context definition and possible context
2417 modifications. Afterwards, changes are achieved with
2418 property-setting commands in the music itself.
2420 Now grob definitions are a special category of context properties.
2421 Since their structure, bookkeeping and use is different from
2422 ordinary context properties, they are accessed with a different
2423 set of commands, and treated separately in the documentation.
2425 As opposed to plain context properties, grob definitions are
2426 subdivided into grob properties. A @qq{grob} (graphical object)
2427 is usually created by an engraver at the time of interpreting a
2428 music expression and receives its initial properties from the
2429 current grob definition of the engraver's context. The engraver
2430 (or other @q{backend} parts of LilyPond) may subsequently add or
2431 change properties to the grob, but that does not affect the
2432 context's grob definition.
2434 What we call @q{grob properties} in the context of user-level
2435 tweaking are actually the properties of a context's grob
2436 definition. In contrast to ordinary context properties, grob
2437 definitions have the bookkeeping required to keep track of its
2438 parts, the individual grob properties (and even subproperties of
2439 them) separately so that it is possible to define those parts in
2440 different contexts and have the overall grob definition at the
2441 time of grob creation be assembled from pieces provided in
2442 different contexts among the current context and its parents.
2444 Grob definitions are manipulated using @code{\override} and
2445 @code{\revert} and have a name starting with a capital letter
2446 (like @samp{NoteHead}) whereas ordinary context properties are
2447 manipulated using @code{\set} and @code{\unset} and are named
2448 starting with a lowercase letter.
2450 @cindex tweak, relation to @code{\override}
2452 @funindex \overrideProperty
2453 The special commands @code{\tweak} and @code{\overrideProperty}
2454 change grob properties bypassing context properties completely.
2455 Instead they catch grobs as they are being created and then
2456 directly set properties on them when they originate from a tweaked
2457 music event or are of a particular kind, respectively.
2459 @node Modifying alists
2460 @subsection Modifying alists
2462 Some user-configurable properties are internally represented as
2463 @emph{alists} (association lists), which store pairs of
2464 @emph{keys} and @emph{values}. The structure of an alist is:
2467 '((@var{key1} . @var{value1})
2468 (@var{key2} . @var{value2})
2469 (@var{key3} . @var{value3})
2473 If an alist is a grob property or @code{\paper} variable, its keys
2474 can be modified individually without affecting other keys.
2476 For example, to reduce the space between adjacent staves in a
2477 staff-group, use the @code{staff-staff-spacing} property of the
2478 @code{StaffGrouper} grob. The property is an alist with four
2479 keys: @code{basic-distance}, @code{minimum-distance},
2480 @code{padding}, and @code{stretchability}. The standard settings
2481 for this property are listed in the @qq{Backend} section of the
2482 Internals Reference (see @rinternals{StaffGrouper}):
2485 '((basic-distance . 9)
2486 (minimum-distance . 7)
2488 (stretchability . 5))
2491 One way to bring the staves closer together is by reducing the
2492 value of the @code{basic-distance} key (@code{9}) to match the
2493 value of @code{minimum-distance} (@code{7}). To modify a single
2494 key individually, use a @emph{nested declaration}:
2496 @lilypond[quote,verbatim]
2497 % default space between staves
2499 \new Staff { \clef treble c''1 }
2500 \new Staff { \clef bass c1 }
2503 % reduced space between staves
2504 \new PianoStaff \with {
2505 % this is the nested declaration
2506 \override StaffGrouper.staff-staff-spacing.basic-distance = #7
2508 \new Staff { \clef treble c''1 }
2509 \new Staff { \clef bass c1 }
2513 Using a nested declaration will update the specified key (such as
2514 @code{basic-distance} in the above example) without altering any
2515 other keys already set for the same property.
2517 Now suppose we want the staves to be as close as possible without
2518 overlapping. The simplest way to do this is to set all four alist
2519 keys to zero. However, it is not necessary to enter four nested
2520 declarations, one for each key. Instead, the property can be
2521 completely re-defined with one declaration, as an alist:
2523 @lilypond[quote,verbatim]
2524 \new PianoStaff \with {
2525 \override StaffGrouper.staff-staff-spacing =
2526 #'((basic-distance . 0)
2527 (minimum-distance . 0)
2529 (stretchability . 0))
2531 \new Staff { \clef treble c''1 }
2532 \new Staff { \clef bass c1 }
2536 Note that any keys not explicitly listed in the alist definition
2537 will be reset to their @emph{default-when-unset} values. In the
2538 case of @code{staff-staff-spacing}, any unset key-values would be
2539 reset to zero (except @code{stretchability}, which takes the value
2540 of @code{basic-distance} when unset). Thus the following two
2541 declarations are equivalent:
2544 \override StaffGrouper.staff-staff-spacing =
2545 #'((basic-distance . 7))
2547 \override StaffGrouper.staff-staff-spacing =
2548 #'((basic-distance . 7)
2549 (minimum-distance . 0)
2551 (stretchability . 7))
2554 One (possibly unintended) consequence of this is the removal of
2555 any standard settings that are set in an initialization file and
2556 loaded each time an input file is compiled. In the above example,
2557 the standard settings for @code{padding} and
2558 @code{minimum-distance} (defined in @file{scm/define-grobs.scm})
2559 are reset to their default-when-unset values (zero for both keys).
2560 Defining a property or variable as an alist (of any size) will
2561 always reset all unset key-values to their default-when-unset
2562 values. Unless this is the intended result, it is safer to update
2563 key-values individually with a nested declaration.
2565 @warning{Nested declarations will not work for context property
2566 alists (such as @code{beamExceptions}, @code{keySignature},
2567 @code{timeSignatureSettings}, etc.). These properties can only be
2568 modified by completely re-defining them as alists.}
2571 @node Useful concepts and properties
2572 @section Useful concepts and properties
2577 * Direction and placement::
2578 * Distances and measurements::
2579 * Staff symbol properties::
2581 * Visibility of objects::
2583 * Rotating objects::
2587 @subsection Input modes
2589 The way in which the notation contained within an input file is
2590 interpreted is determined by the current input mode.
2594 This is activated with the @code{\chordmode} command, and causes
2595 input to be interpreted with the syntax of chord notation, see
2596 @ref{Chord notation}. Chords are rendered as notes on a staff.
2598 Chord mode is also activated with the @code{\chords} command.
2599 This also creates a new @code{ChordNames} context and
2600 causes the following input to be interpreted with the syntax of
2601 chord notation and rendered as chord names in the @code{ChordNames}
2602 context, see @ref{Printing chord names}.
2606 This is activated with the @code{\drummode} command, and causes
2607 input to be interpreted with the syntax of drum notation, see
2608 @ref{Basic percussion notation}.
2610 Drum mode is also activated with the @code{\drums} command.
2611 This also creates a new @code{DrumStaff} context and causes the
2612 following input to be interpreted with the syntax of drum notation
2613 and rendered as drum symbols on a drum staff, see @ref{Basic
2614 percussion notation}.
2616 @strong{Figure mode}
2618 This is activated with the @code{\figuremode} command, and causes
2619 input to be interpreted with the syntax of figured bass, see
2620 @ref{Entering figured bass}.
2622 Figure mode is also activated with the @code{\figures} command.
2623 This also creates a new @code{FiguredBass} context and causes the
2624 following input to be interpreted with the figured bass syntax
2625 and rendered as figured bass symbols in the @code{FiguredBass}
2626 context, see @ref{Introduction to figured bass}.
2628 @strong{Fret and tab modes}
2630 There are no special input modes for entering fret and tab symbols.
2632 To create tab diagrams, enter notes or chords in note mode and
2633 render them in a @code{TabStaff} context, see
2634 @ref{Default tablatures}.
2636 To create fret diagrams above a staff, you have two choices.
2637 You can either use the @code{FretBoards} context (see
2638 @ref{Automatic fret diagrams} or you can enter them as a markup
2639 above the notes using the @code{\fret-diagram} command (see
2640 @ref{Fret diagram markups}).
2642 @strong{Lyrics mode}
2644 This is activated with the @code{\lyricmode} command, and causes
2645 input to be interpreted as lyric syllables with optional durations
2646 and associated lyric modifiers, see @ref{Vocal music}.
2648 Lyric mode is also activated with the @code{\addlyrics} command.
2649 This also creates a new @code{Lyrics} context and an implicit
2650 @code{\lyricsto} command which associates the following lyrics
2651 with the preceding music.
2653 @strong{Markup mode}
2655 This is activated with the @code{\markup} command, and causes
2656 input to be interpreted with the syntax of markup, see
2657 @ref{Text markup commands}.
2659 @c silly work-around for texinfo broken-ness
2660 @c (@strong{Note...} causes a spurious cross-reference in Info)
2663 This is the default mode or it may be activated with the
2664 @code{\notemode} command. Input is interpreted as pitches,
2665 durations, markup, etc and typeset as musical notation on a staff.
2667 It is not normally necessary to specify note mode explicitly, but
2668 it may be useful to do so in certain situations, for example if you
2669 are in lyric mode, chord mode or any other mode and want to insert
2670 something that only can be done with note mode syntax.
2672 For example, to indicate dynamic markings for the verses of a
2673 choral pieces it is necessary to enter note mode to interpret
2676 @lilypond[verbatim,relative=2,quote]
2679 \notemode{\set stanza = \markup{ \dynamic f 1. } }
2683 \notemode{\set stanza = \markup{ \dynamic p 2. } }
2690 @node Direction and placement
2691 @subsection Direction and placement
2693 In typesetting music the direction and placement of many items is
2694 a matter of choice. For example, the stems of notes can
2695 be directed up or down; lyrics, dynamics, and other expressive
2696 marks may be placed above or below the staff; text may be aligned
2697 left, right or center; etc. Most of these choices may be left to
2698 be determined automatically by LilyPond, but in some cases it may
2699 be desirable to force a particular direction or placement.
2702 * Articulation direction indicators::
2703 * The direction property::
2706 @node Articulation direction indicators
2707 @unnumberedsubsubsec Articulation direction indicators
2709 By default some directions are always up or always down (e.g.
2710 dynamics or fermata), while other things can alternate between
2711 up or down based on the stem direction (like slurs or accents).
2713 @c TODO Add table showing these
2715 The default action may be overridden by prefixing the articulation
2716 by a @emph{direction indicator}. Three direction indicators are
2717 available: @code{^} (meaning @qq{up}), @code{_} (meaning @qq{down})
2718 and @code{-} (meaning @qq{use default direction}). The direction
2719 indicator can usually be omitted, in which case @code{-} is assumed,
2720 but a direction indicator is @strong{always} required before
2723 @item @code{\tweak} commands
2724 @item @code{\markup} commands
2725 @item @code{\tag} commands
2726 @item string markups, e.g. -"string"
2727 @item fingering instructions, e.g. @w{@code{-1}}
2728 @item articulation shortcuts, e.g. @w{@code{-.}}, @w{@code{->}}, @w{@code{--}}
2731 Direction indicators affect only the next note:
2733 @lilypond[verbatim,quote,relative=2]
2740 @node The direction property
2741 @unnumberedsubsubsec The direction property
2743 The position or direction of many layout objects is controlled by the
2744 @code{direction} property.
2746 The value of the @code{direction} property may be set to @code{1},
2747 meaning @qq{up} or @qq{above}, or to @w{@code{-1}}, meaning @qq{down} or
2748 @qq{below}. The symbols @code{UP} and @code{DOWN} may be used instead
2749 of @code{1} and @w{@code{-1}} respectively. The default direction may
2750 be specified by setting @code{direction} to @code{0} or @code{CENTER}.
2751 Alternatively, in many cases predefined commands exist to specify the
2752 direction. These are of the form
2755 @code{\xxxUp}, @code{\xxxDown} or @code{\xxxNeutral}
2759 where @code{\xxxNeutral} means @qq{use the default} direction.
2760 See @rlearning{Within-staff objects}.
2762 In a few cases, arpeggio for example, the value of the @code{direction}
2763 property can specify whether the object is to be placed to the right or
2764 left of the parent. In this case @w{@code{-1}} or @code{LEFT} means
2765 @qq{to the left} and @code{1} or @code{RIGHT} means @qq{to the right}.
2766 @code{0} or @code{CENTER} means @qq{use the default} direction.
2769 These all have side-axis set to #X
2770 AmbitusAccidental - direction has no effect
2772 StanzaNumber - not tried
2773 TrillPitchAccidental - not tried
2774 TrillPitchGroup - not tried
2777 These indications affect all notes until they are canceled.
2779 @lilypond[verbatim,quote,relative=2]
2788 In polyphonic music, it is generally better to specify an explicit
2789 @code{voice} than change an object's direction. For more information.
2790 See @ref{Multiple voices}.
2794 @rlearning{Within-staff objects}.
2797 @ref{Multiple voices}.
2800 @node Distances and measurements
2801 @subsection Distances and measurements
2803 @cindex distances, absolute
2804 @cindex distances, scaled
2811 Distances in LilyPond are of two types: absolute and scaled.
2813 Absolute distances are used for specifying margins, indents, and
2814 other page layout details, and are by default specified in
2815 millimeters. Distances may be specified in other units by
2816 following the quantity by @code{\mm}, @code{\cm},
2817 @code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27 of
2818 an inch). Page layout distances can also be specified in scalable
2819 units (see the following paragraph) by appending
2820 @code{\staff-space} to the quantity. Page layout is described in
2821 detail in @ref{Page layout}.
2823 Scaled distances are always specified in units of the staff-space
2824 or, rarely, the half staff-space. The staff-space is the distance
2825 between two adjacent staff lines. The default value can be changed
2826 globally by setting the global staff size, or it can be overridden
2827 locally by changing the @code{staff-space} property of
2828 @code{StaffSymbol}. Scaled distances automatically scale with any
2829 change to the either the global staff size or the
2830 @code{staff-space} property of @code{StaffSymbol}, but fonts scale
2831 automatically only with changes to the global staff size.
2832 The global staff size thus enables the overall size of a rendered
2833 score to be easily varied. For the methods of setting the global
2834 staff size see @ref{Setting the staff size}.
2838 If just a section of a score needs to be rendered to a different
2839 scale, for example an ossia section or a footnote, the global staff
2840 size cannot simply be changed as this would affect the entire score.
2841 In such cases the change in size is made by overriding both the
2842 @code{staff-space} property of @code{StaffSymbol} and the size of
2843 the fonts. A Scheme function, @code{magstep}, is available to
2844 convert from a font size change to the equivalent change in
2845 @code{staff-space}. For an explanation and an example of its use,
2846 see @rlearning{Length and thickness of objects}.
2850 @rlearning{Length and thickness of objects}.
2854 @ref{Setting the staff size}.
2857 @node Staff symbol properties
2858 @subsection Staff symbol properties
2860 @cindex adjusting staff symbol
2861 @cindex drawing staff symbol
2862 @cindex staff symbol, setting of
2864 @c TODO Extend or remove this section. See also NR 1.6.2 Staff symbol
2865 @c Need to think of uses for these properties. Eg 'line-positions
2866 @c is used in a snippet to thicken centre line.
2867 @c If retained, add @ref to here in 1.6.2 -td
2869 The vertical position of staff lines and the number of staff lines
2870 can be defined at the same time. As the following example shows,
2871 note positions are not influenced by the staff line positions.
2873 @warning{The @code{'line-positions} property overrides the
2874 @code{'line-count} property. The number of staff lines is
2875 implicitly defined by the number of elements in the list of values
2876 for @code{'line-positions}.}
2878 @lilypond[verbatim,quote,relative=1]
2880 \override StaffSymbol.line-positions = #'(7 3 0 -4 -6 -7)
2885 The width of a staff can be modified. The units are staff
2886 spaces. The spacing of objects inside the staff is not affected by
2889 @lilypond[verbatim,quote,relative=1]
2891 \override StaffSymbol.width = #23
2898 @subsection Spanners
2900 Many objects of musical notation extend over several notes or even
2901 several bars. Examples are slurs, beams, tuplet brackets, volta
2902 repeat brackets, crescendi, trills, and glissandi. Such objects
2903 are collectively called @qq{spanners}, and have special properties to control
2904 their appearance and behaviour. Some of these properties are common
2905 to all spanners; others are restricted to a sub-set of the spanners.
2907 All spanners support the @code{spanner-interface}. A few, essentially
2908 those that draw a straight line between the two objects, support in
2909 addition the @code{line-spanner-interface}.
2912 * Using the spanner-interface::
2913 * Using the line-spanner-interface::
2916 @node Using the spanner-interface
2917 @unnumberedsubsubsec Using the @code{spanner-interface}
2919 This interface provides two properties that apply to several spanners.
2921 @subsubsubheading The @code{minimum-length} property
2923 The minimum length of the spanner is specified by the
2924 @code{minimum-length} property. Increasing this usually has the
2925 necessary effect of increasing the spacing of the notes between the
2926 two end points. However, this override has no effect on
2927 many spanners, as their length is determined by other considerations.
2928 A few examples where it is effective are shown below.
2938 Works as long as callback is made:
2942 Works not at all for:
2951 @lilypond[verbatim,quote,relative=2]
2954 % increase the length of the tie
2955 -\tweak minimum-length #5
2959 @lilypond[verbatim,quote,relative=2]
2961 \compressFullBarRests
2963 % increase the length of the rest bar
2964 \once \override MultiMeasureRest.minimum-length = #20
2969 @lilypond[verbatim,quote,relative=2]
2971 % increase the length of the hairpin
2972 \override Hairpin.minimum-length = #20
2976 This override can also be used to increase the length of slurs and
2979 @lilypond[verbatim,quote,relative=2]
2982 -\tweak minimum-length #5
2987 -\tweak minimum-length #5
2991 For some layout objects, the @code{minimum-length} property becomes
2992 effective only if the @code{set-spacing-rods} procedure is called
2993 explicitly. To do this, the @code{springs-and-rods} property should
2994 be set to @code{ly:spanner::set-spacing-rods}. For example,
2995 the minimum length of a glissando has no effect unless the
2996 @code{springs-and-rods} property is set:
2998 @lilypond[verbatim,quote,relative=1]
3002 % not effective alone
3003 \once \override Glissando.minimum-length = #20
3006 % effective only when both overrides are present
3007 \once \override Glissando.minimum-length = #20
3008 \once \override Glissando.springs-and-rods = #ly:spanner::set-spacing-rods
3012 The same is true of the @code{Beam} object:
3014 @lilypond[verbatim,quote,relative=1]
3015 % not effective alone
3016 \once \override Beam.minimum-length = #20
3019 % effective only when both overrides are present
3020 \once \override Beam.minimum-length = #20
3021 \once \override Beam.springs-and-rods = #ly:spanner::set-spacing-rods
3025 @subsubsubheading The @code{to-barline} property
3027 The second useful property of the @code{spanner-interface} is
3028 @code{to-barline}. By default this is true, causing hairpins and
3029 other spanners which are terminated on the first note of a measure to
3030 end instead on the immediately preceding bar line. If set to false,
3031 the spanner will extend beyond the bar line and end on the note
3034 @lilypond[verbatim,quote,relative=2]
3035 a \< a a a a \! a a a \break
3036 \override Hairpin.to-barline = ##f
3037 a \< a a a a \! a a a
3040 This property is not effective for all spanners. For example,
3041 setting it to @code{#t} has no effect on slurs or phrasing slurs
3042 or on other spanners for which terminating on the bar line would
3045 @node Using the line-spanner-interface
3046 @unnumberedsubsubsec Using the @code{line-spanner-interface}
3048 Objects which support the @code{line-spanner-interface} include
3051 @item @code{DynamicTextSpanner}
3052 @item @code{Glissando}
3053 @item @code{TextSpanner}
3054 @item @code{TrillSpanner}
3055 @item @code{VoiceFollower}
3058 The routine responsible for drawing the stencils for these spanners is
3059 @code{ly:line-interface::print}. This routine determines the
3060 exact location of the two end points and draws a line
3061 between them, in the style requested. The locations of the two
3062 end points of the spanner are computed on-the-fly, but it is
3063 possible to override their Y-coordinates. The
3064 properties which need to be specified are nested
3065 two levels down within the property hierarchy, but the syntax of
3066 the @code{\override} command is quite simple:
3068 @lilypond[relative=2,quote,verbatim]
3070 \once \override Glissando.bound-details.left.Y = #3
3071 \once \override Glissando.bound-details.right.Y = #-2
3075 The units for the @code{Y} property are @code{staff-space}s,
3076 with the center line of the staff being the zero point.
3077 For the glissando, this is the value for @code{Y} at the
3078 X-coordinate corresponding to the center point of each note head,
3079 if the line is imagined to be extended to there.
3081 If @code{Y} is not set, the value is computed from the vertical
3082 position of the corresponding attachment point of the spanner.
3084 In case of a line break, the values for the end points are
3085 specified by the @code{left-broken} and @code{right-broken}
3086 sub-lists of @code{bound-details}. For example:
3088 @lilypond[relative=2,ragged-right,verbatim,quote]
3089 \override Glissando.breakable = ##t
3090 \override Glissando.bound-details.right-broken.Y = #-3
3091 c1 \glissando \break
3096 A number of further properties of the @code{left} and
3097 @code{right} sub-lists of the @code{bound-details} property
3098 may be modified in the same way as @code{Y}:
3102 This sets the Y-coordinate of the end point, in @code{staff-space}s
3103 offset from the staff center line. By default, it is the center of
3104 the bound object, so a glissando points to the vertical center of
3107 For horizontal spanners, such as text spanners and trill spanners,
3108 it is hardcoded to 0.
3111 This determines where the line starts and ends in the X-direction,
3112 relative to the bound object. So, a value of @w{@code{-1}} (or
3113 @code{LEFT}) makes the line start/end at the left side of the note
3114 head it is attached to.
3117 This is the absolute X-coordinate of the end point. It is usually
3118 computed on the fly, and overriding it has little useful effect.
3121 Line spanners may have symbols at the beginning or end, which is
3122 contained in this sub-property. This is for internal use; it is
3123 recommended that @code{text} be used instead.
3126 This is a markup that is evaluated to yield the stencil. It is used
3127 to put @i{cresc.}, @i{tr} and other text on horizontal spanners.
3129 @lilypond[quote,ragged-right,relative=2,verbatim]
3130 \override TextSpanner.bound-details.left.text
3131 = \markup { \small \bold Slower }
3132 c2\startTextSpan b c a\stopTextSpan
3135 @item stencil-align-dir-y
3136 @item stencil-offset
3137 Without setting one of these, the stencil is simply put at the
3138 end-point, centered on the line, as defined by the @code{X} and
3139 @code{Y} sub-properties. Setting either @code{stencil-align-dir-y}
3140 or @code{stencil-offset} will move the symbol at the edge vertically
3141 relative to the end point of the line:
3143 @lilypond[relative=1,quote,verbatim]
3144 \override TextSpanner.bound-details.left.stencil-align-dir-y = #-2
3145 \override TextSpanner.bound-details.right.stencil-align-dir-y = #UP
3147 \override TextSpanner.bound-details.left.text = #"ggg"
3148 \override TextSpanner.bound-details.right.text = #"hhh"
3149 c4^\startTextSpan c c c \stopTextSpan
3152 Note that negative values move the text @emph{up}, contrary to the
3153 effect that might be expected, as a value of @w{@code{-1}} or
3154 @code{DOWN} means align the @emph{bottom} edge of the text with
3155 the spanner line. A value of @code{1} or @code{UP} aligns
3156 the top edge of the text with the spanner line.
3159 Setting this sub-property to @code{#t} produces an arrowhead at the
3163 This sub-property controls the space between the specified
3164 end point of the line and the actual end. Without padding, a
3165 glissando would start and end in the center of each note head.
3169 The music function @code{\endSpanners} terminates the spanner
3170 which starts on the immediately following note prematurely. It
3171 is terminated after exactly one note, or at the following bar line
3172 if @code{to-barline} is true and a bar line occurs before the next
3175 @lilypond[verbatim,quote,ragged-right,relative=2]
3177 c2 \startTextSpan c2 c2
3182 When using @code{\endSpanners} it is not necessary to close
3183 \startTextSpan with \stopTextSpan, nor is it necessary to close
3184 hairpins with @code{\!}.
3187 Internals Reference:
3188 @rinternals{TextSpanner},
3189 @rinternals{Glissando},
3190 @rinternals{VoiceFollower},
3191 @rinternals{TrillSpanner},
3192 @rinternals{line-spanner-interface}.
3195 @node Visibility of objects
3196 @subsection Visibility of objects
3198 @cindex objects, visibility of
3199 @cindex grobs, visibility of
3200 @cindex visibility of objects
3202 There are four main ways in which the visibility of layout objects
3203 can be controlled: their stencil can be removed, they can be made
3204 transparent, they can be colored white, or their
3205 @code{break-visibility} property can be overridden. The first
3206 three apply to all layout objects; the last to just a few -- the
3207 @emph{breakable} objects. The Learning Manual introduces these
3208 four techniques, see @rlearning{Visibility and color of objects}.
3210 There are also a few other techniques which are specific to
3211 certain layout objects. These are covered under Special
3215 * Removing the stencil::
3216 * Making objects transparent::
3217 * Painting objects white::
3218 * Using break-visibility::
3219 * Special considerations::
3223 @node Removing the stencil
3224 @unnumberedsubsubsec Removing the stencil
3226 @cindex stencil, removing
3229 Every layout object has a stencil property. By default this is set
3230 to the specific function which draws that object. If this property
3231 is overridden to @code{#f} no function will be called and the object
3232 will not be drawn. The default action can be recovered with
3235 @lilypond[quote,verbatim,relative=1]
3237 \override Score.BarLine.stencil = ##f
3239 \revert Score.BarLine.stencil
3243 This rather common operation has a shortcut @code{\omit}:
3245 @lilypond[quote,verbatim,relative=1]
3249 \undo \omit Score.BarLine
3253 @node Making objects transparent
3254 @unnumberedsubsubsec Making objects transparent
3256 @cindex transparent, making objects
3259 Every layout object has a transparent property which by default is
3260 set to @code{#f}. If set to @code{#t} the object still occupies
3261 space but is made invisible.
3263 @lilypond[quote,verbatim,relative=2]
3265 \once \override NoteHead.transparent = ##t
3269 This rather common operation has a shortcut @code{\hide}:
3271 @lilypond[quote,verbatim,relative=2]
3273 \once \hide NoteHead
3277 @node Painting objects white
3278 @unnumberedsubsubsec Painting objects white
3280 @cindex objects, coloring
3281 @cindex coloring objects
3283 @cindex printing order
3284 @cindex overwriting objects
3285 @cindex objects, overwriting
3286 @cindex grobs, overwriting
3288 Every layout object has a color property which by default is set
3289 to @code{black}. If this is overridden to @code{white} the object
3290 will be indistinguishable from the white background. However,
3291 if the object crosses other objects the color of the crossing
3292 points will be determined by the order in which they are drawn,
3293 and this may leave a ghostly image of the white object, as shown
3296 @lilypond[quote,verbatim,relative=2]
3297 \override Staff.Clef.color = #white
3301 This may be avoided by changing the order of printing the objects.
3302 All layout objects have a @code{layer} property which should be set
3303 to an integer. Objects with the lowest value of @code{layer} are
3304 drawn first, then objects with progressively higher values are drawn,
3305 so objects with higher values overwrite objects with lower values.
3306 By default most objects are assigned a @code{layer} value of
3307 @code{1}, although a few objects, including @code{StaffSymbol} and
3308 @code{BarLine}, are assigned a value of @code{0}. The order of
3309 printing objects with the same value of @code{layer} is indeterminate.
3311 In the example above the white clef, with a default @code{layer}
3312 value of @code{1}, is drawn after the staff lines (default
3313 @code{layer} value @code{0}), so overwriting them. To change this,
3314 the @code{Clef} object must be given in a lower value of
3315 @code{layer}, say @w{@code{-1}}, so that it is drawn earlier:
3317 @lilypond[quote,verbatim,relative=2]
3318 \override Staff.Clef.color = #white
3319 \override Staff.Clef.layer = #-1
3323 @node Using break-visibility
3324 @unnumberedsubsubsec Using break-visibility
3326 @c TODO Add making other objects breakable
3328 @cindex break-visibility
3330 Most layout objects are printed only once, but some like
3331 bar lines, clefs, time signatures and key signatures, may need
3332 to be printed twice when a line break occurs -- once at the end
3333 of the line and again at the start of the next line. Such
3334 objects are called @emph{breakable}, and have a property, the
3335 @code{break-visibility} property to control their visibility
3336 at the three positions in which they may appear -- at the
3337 start of a line, within a line if they are changed, and at the
3338 end of a line if a change takes place there.
3340 For example, the time signature
3341 by default will be printed at the start of the first line, but
3342 nowhere else unless it changes, when it will be printed at the
3343 point at which the change occurs. If this change occurs at the
3344 end of a line the new time signature will be printed at the start
3345 of the next line and a cautionary time signature will be printed
3346 at the end of the previous line as well.
3348 This behaviour is controlled by the @code{break-visibility}
3349 property, which is explained in
3350 @c Leave this ref on a newline - formats incorrectly otherwise -td
3351 @rlearning{Visibility and color of objects}. This property takes
3352 a vector of three booleans which, in order, determine whether the
3353 object is printed at the end of, within the body of, or at the
3354 beginning of a line. Or to be more precise, before a line break,
3355 where there is no line break, or after a line break.
3357 Alternatively, these eight combinations may be specified
3358 by pre-defined functions, defined in @file{scm/output-lib.scm},
3359 where the last three columns indicate whether the layout objects
3360 will be visible in the positions shown at the head of the columns:
3362 @multitable {@code{begin-of-line-invisible}} {@code{'#(#t #t #t)}} {Before} {At no} {After}
3363 @headitem Function @tab Vector @tab Before @tab At no @tab After
3364 @headitem form @tab form @tab break @tab break @tab break
3366 @item @code{all-visible} @tab @code{'#(#t #t #t)} @tab yes @tab yes @tab yes
3367 @item @code{begin-of-line-visible} @tab @code{'#(#f #f #t)} @tab no @tab no @tab yes
3368 @item @code{center-visible} @tab @code{'#(#f #t #f)} @tab no @tab yes @tab no
3369 @item @code{end-of-line-visible} @tab @code{'#(#t #f #f)} @tab yes @tab no @tab no
3370 @item @code{begin-of-line-invisible} @tab @code{'#(#t #t #f)} @tab yes @tab yes @tab no
3371 @item @code{center-invisible} @tab @code{'#(#t #f #t)} @tab yes @tab no @tab yes
3372 @item @code{end-of-line-invisible} @tab @code{'#(#f #t #t)} @tab no @tab yes @tab yes
3373 @item @code{all-invisible} @tab @code{'#(#f #f #f)} @tab no @tab no @tab no
3376 The default settings of @code{break-visibility} depend on the
3377 layout object. The following table shows all the layout objects
3378 of interest which are affected by @code{break-visibility} and the
3379 default setting of this property:
3381 @multitable @columnfractions .3 .3 .4
3383 @headitem Layout object @tab Usual context @tab Default setting
3385 @c omit Ambitus as it appears not to be affected by break-visibility -td
3386 @c @item @code{Ambitus} @tab as specified @tab @code{begin-of-line-visible}
3387 @item @code{BarLine} @tab @code{Score} @tab calculated
3388 @item @code{BarNumber} @tab @code{Score} @tab @code{begin-of-line-visible}
3389 @c omit the following item until it can be explained -td
3390 @c @item @code{BreakAlignGroup} @tab @code{Score} @tab calculated
3391 @item @code{BreathingSign} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3392 @item @code{Clef} @tab @code{Staff} @tab @code{begin-of-line-visible}
3393 @item @code{Custos} @tab @code{Staff} @tab @code{end-of-line-visible}
3394 @item @code{DoublePercentRepeat} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3395 @item @code{KeyCancellation} @tab @code{Staff} @tab @code{begin-of-line-invisible}
3396 @item @code{KeySignature} @tab @code{Staff} @tab @code{begin-of-line-visible}
3397 @c omit LeftEdge until it can be explained -td
3398 @c @item @code{LeftEdge} @tab @code{Score} @tab @code{center-invisible}
3399 @item @code{ClefModifier} @tab @code{Staff} @tab @code{begin-of-line-visible}
3400 @item @code{RehearsalMark} @tab @code{Score} @tab @code{end-of-line-invisible}
3401 @item @code{TimeSignature} @tab @code{Staff} @tab @code{all-visible}
3405 The example below shows the use of the vector form to control the
3406 visibility of bar lines:
3408 @lilypond[quote,verbatim,relative=1,ragged-right]
3411 % Remove bar line at the end of the current line
3412 \once \override Score.BarLine.break-visibility = ##(#f #t #t)
3418 Although all three components of the vector used to override
3419 @code{break-visibility} must be present, not all of them are
3420 effective with every layout object, and some combinations may
3421 even give errors. The following limitations apply:
3424 @item Bar lines cannot be printed at start of line.
3425 @item A bar number cannot be printed at the start of the first
3426 line unless it is set to be different from 1.
3427 @item Clef -- see below
3428 @item Double percent repeats are either all printed or all
3429 suppressed. Use begin-of line-invisible to print and
3430 all-invisible to suppress.
3431 @item Key signature -- see below
3432 @item ClefModifier -- see below
3435 @node Special considerations
3436 @unnumberedsubsubsec Special considerations
3438 @subsubsubheading Visibility following explicit changes
3440 @cindex key signature, visibility following explicit change
3441 @cindex explicitKeySignatureVisibility
3442 @cindex clef, visibility following explicit change
3443 @cindex explicitClefVisibility
3445 The @code{break-visibility} property controls the visibility of
3446 key signatures and changes of clef only at the start of lines,
3447 i.e. after a break. It has no effect on the visibility of the
3448 key signature or clef following an explicit key change or an
3449 explicit clef change within or at the end of a line. In the
3450 following example the key signature following the explicit change
3451 to B-flat major is still visible, even though @code{all-invisible}
3454 @lilypond[quote,verbatim,relative=1,ragged-right]
3457 % Try to remove all key signatures
3458 \override Staff.KeySignature.break-visibility = #all-invisible
3466 The visibility of such explicit key signature and clef changes is
3467 controlled by the @code{explicitKeySignatureVisibility} and
3468 @code{explicitClefVisibility} properties. These are the equivalent
3469 of the @code{break-visibility} property and both take a vector of
3470 three booleans or the predefined functions listed above, exactly like
3471 @code{break-visibility}. Both are properties of the Staff context,
3472 not the layout objects themselves, and so they are set using the
3473 @code{\set} command. Both are set by default to @code{all-visible}.
3474 These properties control only the visibility of key signatures and
3475 clefs resulting from explicit changes and do not affect key
3476 signatures and clefs at the beginning of lines;
3477 @code{break-visibility} must still be overridden in the appropriate
3478 object to remove these.
3480 @lilypond[quote,verbatim,relative=1,ragged-right]
3483 \set Staff.explicitKeySignatureVisibility = #all-invisible
3484 \override Staff.KeySignature.break-visibility = #all-invisible
3491 @subsubsubheading Visibility of cancelling accidentals
3493 To remove the cancelling accidentals printed at an explicit key
3494 change, set the Staff context property @code{printKeyCancellation}
3497 @lilypond[quote,verbatim,relative=1,ragged-right]
3500 \set Staff.explicitKeySignatureVisibility = #all-invisible
3501 \set Staff.printKeyCancellation = ##f
3502 \override Staff.KeySignature.break-visibility = #all-invisible
3509 With these overrides only the accidentals before the notes remain
3510 to indicate the change of key.
3512 Note that when changing the key to C@tie{}major or A@tie{}minor
3513 the cancelling accidentals would be the @emph{only} indication of
3514 the key change. In this case setting @code{printKeyCancellation} to
3515 @code{#f} has no effect:
3517 @lilypond[quote,verbatim,relative=1,ragged-right]
3520 \set Staff.explicitKeySignatureVisibility = #all-invisible
3521 \set Staff.printKeyCancellation = ##f
3528 To suppress the cancelling accidentals even when the key is
3529 changed to C@tie{}major or A@tie{}minor, override
3530 the visibility of the @code{KeyCancellation} grob instead:
3532 @lilypond[quote,verbatim,relative=1,ragged-right]
3535 \set Staff.explicitKeySignatureVisibility = #all-invisible
3536 \override Staff.KeyCancellation.break-visibility = #all-invisible
3543 @c TODO Add visibility of cautionary accidentals before notes
3545 @subsubsubheading Automatic bars
3547 @cindex automaticBars
3548 @cindex bar lines, suppressing
3550 As a special case, the printing of bar lines can also be turned off
3551 by setting the @code{automaticBars} property in the Score context.
3552 If set to @code{#f}, bar lines will not be printed automatically;
3553 they must be explicitly created with a @code{\bar} command. Unlike
3554 the @code{\cadenzaOn} predefined command, measures are still counted.
3555 Bar generation will resume according to that count if this property
3556 is later set to @code{#t}. When set to @code{#f}, line breaks can
3557 occur only at explicit @code{\bar} commands.
3561 @subsubsubheading Transposed clefs
3563 @cindex transposed clefs, visibility of
3564 @cindex visibility of transposed clefs
3565 @cindex clefs, visibility of transposition
3567 The small transposition symbol on transposed clefs is produced by the
3568 @code{ClefModifier} layout object. Its visibility is automatically
3569 inherited from the @code{Clef} object, so it is not necessary to apply
3570 any required @code{break-visibility} overrides to the @code{ClefModifier}
3571 layout objects to suppress transposition symbols for invisible clefs.
3573 For explicit clef changes, the @code{explicitClefVisibility}
3574 property controls both the clef symbol and any transposition symbol
3579 @rlearning{Visibility and color of objects}.
3583 @subsection Line styles
3585 Some performance indications, e.g., @i{rallentando} and
3586 @i{accelerando} and @i{trills} are written as text and are
3587 extended over many measures with lines, sometimes dotted or wavy.
3589 These all use the same routines as the glissando for drawing the
3590 texts and the lines, and tuning their behavior is therefore also
3591 done in the same way. It is done with a spanner, and the routine
3592 responsible for drawing the spanners is
3593 @code{ly:line-interface::print}. This routine determines the
3594 exact location of the two @i{span points} and draws a line
3595 between them, in the style requested.
3597 Here is an example showing the different line styles available,
3598 and how to tune them.
3600 @lilypond[relative=2,ragged-right,verbatim,quote]
3602 \once \override Glissando.style = #'dashed-line
3604 \override Glissando.style = #'dotted-line
3606 \override Glissando.style = #'zigzag
3608 \override Glissando.style = #'trill
3612 The locations of the end-points of the spanner are computed
3613 on-the-fly for every graphic object, but it is possible to
3617 @lilypond[relative=2,ragged-right,verbatim,quote]
3619 \once \override Glissando.bound-details.right.Y = #-2
3623 The value for @code{Y} is set to @w{@code{-2}} for the right end
3624 point. The left side may be similarly adjusted by specifying
3625 @code{left} instead of @code{right}.
3627 If @code{Y} is not set, the value is computed from the vertical
3628 position of the left and right attachment points of the spanner.
3630 Other adjustments of spanners are possible, for details, see
3633 @node Rotating objects
3634 @subsection Rotating objects
3636 Both layout objects and elements of markup text can be rotated by
3637 any angle about any point, but the method of doing so differs.
3640 * Rotating layout objects::
3644 @node Rotating layout objects
3645 @unnumberedsubsubsec Rotating layout objects
3647 @cindex rotating objects
3648 @cindex objects, rotating
3650 All layout objects which support the @code{grob-interface} can be
3651 rotated by setting their @code{rotation} property. This takes a
3652 list of three items: the angle of rotation counter-clockwise,
3653 and the x and y coordinates of the point relative to the object's
3654 reference point about which the rotation is to be performed. The
3655 angle of rotation is specified in degrees and the coordinates in
3658 The angle of rotation and the coordinates of the rotation point must
3659 be determined by trial and error.
3661 @cindex hairpins, angled
3662 @cindex angled hairpins
3664 There are only a few situations where the rotation of layout
3665 objects is useful; the following example shows one situation where
3668 @lilypond[quote,verbatim,relative=1]
3670 \override Hairpin.rotation = #'(20 -1 0)
3674 @node Rotating markup
3675 @unnumberedsubsubsec Rotating markup
3677 All markup text can be rotated to lie at any angle by prefixing it
3678 with the @code{\rotate} command. The command takes two arguments:
3679 the angle of rotation in degrees counter-clockwise and the text to
3680 be rotated. The extents of the text are not rotated: they take
3681 their values from the extremes of the x and y coordinates of the
3682 rotated text. In the following example the
3683 @code{outside-staff-priority} property for text is set to @code{#f}
3684 to disable the automatic collision avoidance, which would push some
3685 of the text too high.
3687 @lilypond[quote,verbatim,relative=1]
3688 \override TextScript.outside-staff-priority = ##f
3689 g4^\markup { \rotate #30 "a G" }
3690 b^\markup { \rotate #30 "a B" }
3691 des^\markup { \rotate #30 "a D-Flat" }
3692 fis^\markup { \rotate #30 "an F-Sharp" }
3695 @node Advanced tweaks
3696 @section Advanced tweaks
3698 This section discusses various approaches to fine tuning the
3699 appearance of the printed score.
3702 * Aligning objects::
3703 * Vertical grouping of grobs::
3704 * Modifying stencils::
3705 * Modifying shapes::
3706 * Modifying broken spanners::
3707 * Unpure-pure containers::
3712 @rlearning{Tweaking output},
3713 @rlearning{Other sources of information}.
3716 @ref{Explaining the Internals Reference},
3717 @ref{Modifying properties}.
3720 @rextend{Interfaces for programmers}.
3723 @file{scm/define-grobs.scm}.
3726 @rlsr{Tweaks and overrides}.
3728 Internals Reference:
3729 @rinternals{All layout objects}.
3732 @node Aligning objects
3733 @subsection Aligning objects
3735 Graphical objects which support the @code{self-alignment-interface}
3736 and/or the @code{side-position-interface} can be aligned to a previously
3737 placed object in a variety of ways. For a list of these objects, see
3738 @rinternals{self-alignment-interface} and @rinternals{side-position-interface}.
3740 All graphical objects have a reference point, a horizontal extent and a
3741 vertical extent. The horizontal extent is a pair of numbers
3742 giving the displacements from the reference point of the left and
3743 right edges, displacements to the left being negative. The vertical
3744 extent is a pair of numbers giving the displacement from the reference
3745 point to the bottom and top edges, displacements down being negative.
3747 An object's position on a staff is given by the values of the
3748 @code{X-offset} and @code{Y-offset} properties. The value of
3749 @code{X-offset} gives the displacement from the X coordinate of
3750 the reference point of the parent object, and the value of
3751 @code{Y-offset} gives the displacement from the center line of the
3752 staff. The values of @code{X-offset} and @code{Y-offset} may
3753 be set directly or may be set to be calculated by procedures in order
3754 to achieve alignment with the parent object.
3756 @warning{Many objects have special positioning considerations which
3757 cause any setting of @code{X-offset} or @code{Y-offset} to be
3758 ignored or modified, even though the object supports the
3759 @code{self-alignment-interface}. Overriding the @code{X-offset}
3760 or @code{Y-offset} properties to a fixed value causes the respective
3761 @code{self-alignment} property to be disregarded.}
3763 For example, an accidental can be repositioned vertically by setting
3764 @code{Y-offset} but any changes to @code{X-offset} have no effect.
3766 Rehearsal marks may be aligned with breakable objects such as bar
3767 lines, clef symbols, time signature symbols and key signatures. There
3768 are special properties to be found in the @code{break-aligned-interface}
3769 for positioning rehearsal marks on such objects.
3773 @ref{Using the break-alignable-interface}.
3776 @rextend{Callback functions}.
3779 * Setting X-offset and Y-offset directly::
3780 * Using the side-position-interface::
3781 * Using the self-alignment-interface::
3782 * Using the break-alignable-interface::
3785 @node Setting X-offset and Y-offset directly
3786 @unnumberedsubsubsec Setting @code{X-offset} and @code{Y-offset} directly
3788 Numerical values may be given to the @code{X-offset} and @code{Y-offset}
3789 properties of many objects. The following example shows three
3790 notes with the default fingering position and the positions with @code{X-offset}
3791 and @code{Y-offset} modified.
3793 @lilypond[verbatim,quote,relative=2]
3800 -\tweak X-offset #-1
3807 @node Using the side-position-interface
3808 @unnumberedsubsubsec Using the @code{side-position-interface}
3810 An object which supports the @code{side-position-interface} can be
3811 placed next to its parent object so that
3812 the specified edges of the two objects touch. The object may be
3813 placed above, below, to the right or to the left of the parent.
3814 The parent cannot be specified; it is determined by the order of
3815 elements in the input stream. Most objects have the associated
3816 note head as their parent.
3818 The values of the @code{side-axis} and @code{direction} properties
3819 determine where the object is to be placed, as follows:
3821 @c TODO add an example of each to the table
3823 @multitable @columnfractions .3 .3 .3
3824 @headitem @code{side-axis} @tab @code{direction} @tab
3825 @headitem property @tab property @tab Placement
3827 @item @code{0} @tab @code{-1} @tab left
3828 @item @code{0} @tab @code{1} @tab right
3829 @item @code{1} @tab @code{-1} @tab below
3830 @item @code{1} @tab @code{1} @tab above
3834 When @code{side-axis} is @code{0}, @code{X-offset} should be set to
3835 the procedure @code{ly:side-position-interface::x-aligned-side}.
3836 This procedure will return the correct value of @code{X-offset} to
3837 place the object to the left or right side of the parent according
3838 to value of @code{direction}.
3840 When @code{side-axis} is @code{1}, @code{Y-offset} should be set to
3841 the procedure @code{ly:side-position-interface::y-aligned-side}.
3842 This procedure will return the correct value of @code{Y-offset} to
3843 place the object to the top or bottom of the parent according
3844 to value of @code{direction}.
3846 @c TODO Add examples
3848 @node Using the self-alignment-interface
3849 @unnumberedsubsubsec Using the @code{self-alignment-interface}
3851 @subsubsubheading Self-aligning objects horizontally
3853 The horizontal alignment of an object which supports the
3854 @code{self-alignment-interface} is controlled by the value of
3855 the @code{self-alignment-X} property, provided the object's
3856 @code{X-offset} property is set to
3857 @code{ly:self-alignment-interface::x-aligned-on-self}.
3858 @code{self-alignment-X} may be given any
3859 real value, in units of half the total X extent of the
3860 object. Negative values move the object to the right, positive
3861 to the left. A value of @code{0} centers the object on the
3862 reference point of its parent, a value of @w{@code{-1}} aligns the
3863 left edge of the object on the reference point of its parent,
3864 and a value of @code{1} aligns the right edge of the object on the
3865 reference point of its parent. The symbols @code{LEFT},
3866 @code{CENTER}, and @code{RIGHT} may be used instead of the values
3867 @w{@code{-1}}, @code{0}, and @code{1}, respectively.
3869 Normally the @code{\override} command would be used to modify the
3870 value of @code{self-alignment-X}, but the @code{\tweak} command
3871 can be used to separately align several annotations on a single
3874 @lilypond[quote,verbatim,relative=1]
3876 -\tweak self-alignment-X #-1
3878 -\tweak self-alignment-X #0
3880 -\tweak self-alignment-X #RIGHT
3882 -\tweak self-alignment-X #-2.5
3883 ^"aligned further to the right"
3886 @subsubsubheading Self-aligning objects vertically
3888 Objects may be aligned vertically in an analogous way to aligning
3889 them horizontally if the @code{Y-offset} property is set to
3890 @code{ly:self-alignment-interface::y-aligned-on-self}. However,
3891 other mechanisms are often involved in vertical alignment: the
3892 value of @code{Y-offset} is just one variable taken into account.
3893 This may make adjusting the value of some objects tricky.
3894 The units are just half the vertical extent of the object, which
3895 is usually quite small, so quite large numbers may be required.
3896 A value of @w{@code{-1}} aligns the lower edge of the object with
3897 the reference point of the parent object, a value of @code{0}
3898 aligns the center of the object with the reference point of the
3899 parent, and a value of @code{1} aligns the top edge of the object
3900 with the reference point of the parent. The symbols @code{DOWN},
3901 @code{CENTER}, and @code{UP} may be substituted for @w{@code{-1}},
3902 @code{0}, and @code{1}, respectively.
3904 @subsubsubheading Self-aligning objects in both directions
3906 By setting both @code{X-offset} and @code{Y-offset}, an object may
3907 be aligned in both directions simultaneously.
3909 The following example shows how to adjust a fingering mark so
3910 that it nestles close to the note head.
3912 @lilypond[quote,verbatim,relative=2]
3914 -\tweak self-alignment-X #0.5 % move horizontally left
3915 -\tweak Y-offset #ly:self-alignment-interface::y-aligned-on-self
3916 -\tweak self-alignment-Y #-1 % move vertically up
3921 @unnumberedsubsubsec Using the @code{aligned-on-parent} procedures
3923 @c Cannot document as they do not seem to operate consistently on all objects -td
3924 @c TODO investigate further
3926 The @code{aligned-on-parent} procedures are used in the same way
3927 as the @code{aligned-on-self} procedures, they difference being
3928 that they permit an object to be aligned with the @emph{edges} of
3929 the parent rather than the parent's reference point. The following
3930 example shows the difference:
3934 @lilypond[verbatim,quote]
3940 @unnumberedsubsubsec Using the @code{centered-on-parent} procedures
3942 @c Cannot document as they do not seem to operate consistently on all objects -td
3943 @c TODO investigate further
3947 @c TODO The align-interface, BassFigureAlignment and VerticalAlignment
3949 @node Using the break-alignable-interface
3950 @unnumberedsubsubsec Using the @code{break-alignable-interface}
3952 @cindex align to objects
3953 @cindex break-align-symbols
3955 Rehearsal marks and bar numbers may be aligned with notation
3956 objects other than bar lines. These objects include @code{ambitus},
3957 @code{breathing-sign}, @code{clef}, @code{custos}, @code{staff-bar},
3958 @code{left-edge}, @code{key-cancellation}, @code{key-signature}, and
3959 @code{time-signature}.
3961 Each type of object has its own default reference point, to which
3962 rehearsal marks are aligned:
3964 @lilypond[verbatim,quote,relative=1]
3965 % The rehearsal mark will be aligned to the right edge of the Clef
3966 \override Score.RehearsalMark.break-align-symbols = #'(clef)
3971 % The rehearsal mark will be aligned to the left edge of the Time Signature
3972 \override Score.RehearsalMark.break-align-symbols = #'(time-signature)
3978 % The rehearsal mark will be centered above the Breath Mark
3979 \override Score.RehearsalMark.break-align-symbols = #'(breathing-sign)
3988 A list of possible target alignment objects may be specified. If
3989 some of the objects are invisible at that point due to the setting
3990 of @code{break-visibility} or the explicit visibility settings for
3991 keys and clefs, the rehearsal mark or bar number is aligned to the
3992 first object in the list which is visible. If no objects in the
3993 list are visible the object is aligned to the bar line. If the bar
3994 line is invisible the object is aligned to the place where the bar
3997 @lilypond[verbatim,quote,relative=1]
3998 % The rehearsal mark will be aligned to the right edge of the Key Signature
3999 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4004 % The rehearsal mark will be aligned to the right edge of the Clef
4005 \set Staff.explicitKeySignatureVisibility = #all-invisible
4006 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4011 % The rehearsal mark will be centered above the Bar Line
4012 \set Staff.explicitKeySignatureVisibility = #all-invisible
4013 \set Staff.explicitClefVisibility = #all-invisible
4014 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4021 The alignment of the rehearsal mark relative to the notation object
4022 can be changed, as shown in the following example. In a score with
4023 multiple staves, this setting should be done for all the staves.
4025 @lilypond[verbatim,quote,relative=1]
4026 % The RehearsalMark will be aligned with the right edge of the Key Signature
4027 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4033 % The RehearsalMark will be centered above the Key Signature
4034 \once \override Score.KeySignature.break-align-anchor-alignment = #CENTER
4038 % The RehearsalMark will be aligned with the left edge of the Key Signature
4039 \once \override Score.KeySignature.break-align-anchor-alignment = #LEFT
4045 The rehearsal mark can also be offset to the right or left of the left
4046 edge by an arbitrary amount. The units are staff-spaces:
4048 @lilypond[verbatim,quote,relative=1]
4049 % The RehearsalMark will be aligned with the left edge of the Key Signature
4050 % and then shifted right by 3.5 staff-spaces
4051 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4052 \once \override Score.KeySignature.break-align-anchor = #3.5
4056 % The RehearsalMark will be aligned with the left edge of the Key Signature
4057 % and then shifted left by 2 staff-spaces
4058 \once \override Score.KeySignature.break-align-anchor = #-2
4065 @node Vertical grouping of grobs
4066 @subsection Vertical grouping of grobs
4068 @c TODO Expand this section
4070 The VerticalAlignment and VerticalAxisGroup grobs work together.
4071 VerticalAxisGroup groups together different grobs like Staff, Lyrics,
4072 etc. VerticalAlignment then vertically aligns the different grobs
4073 grouped together by VerticalAxisGroup. There is usually only one
4074 VerticalAlignment per score but every Staff, Lyrics, etc. has its own
4078 @node Modifying stencils
4079 @subsection Modifying stencils
4081 All layout objects have a @code{stencil} property which is part of
4082 the @code{grob-interface}. By default, this property is usually
4083 set to a function specific to the object that is tailor-made to
4084 render the symbol which represents it in the output. For example,
4085 the standard setting for the @code{stencil} property of the
4086 @code{MultiMeasureRest} object is @code{ly:multi-measure-rest::print}.
4088 The standard symbol for any object can be replaced by modifying the
4089 @code{stencil} property to reference a different, specially-written,
4090 procedure. This requires a high level of knowledge of the internal
4091 workings of LilyPond, but there is an easier way which can often
4092 produce adequate results.
4094 This is to set the @code{stencil} property to the procedure which
4095 prints text -- @code{ly:text-interface::print} -- and to add a
4096 @code{text} property to the object which is set to contain the
4097 markup text which produces the required symbol. Due to the
4098 flexibility of markup, much can be achieved -- see in particular
4099 @ref{Graphic notation inside markup}.
4101 The following example demonstrates this by changing the note head
4102 symbol to a cross within a circle.
4104 @lilypond[verbatim,quote]
4106 \once \override NoteHead.stencil = #ly:text-interface::print
4107 \once \override NoteHead.text = \markup {
4109 \halign #-0.7 \draw-circle #0.85 #0.2 ##f
4110 \musicglyph #"noteheads.s2cross"
4118 Any of the glyphs in the feta Font can be supplied to the
4119 @code{\musicglyph} markup command -- see @ref{The Feta font}.
4121 @c TODO Add inserting eps files or ref to later
4123 @c TODO Add inserting Postscript or ref to later
4127 @ref{Graphic notation inside markup},
4128 @ref{Formatting text},
4129 @ref{Text markup commands},
4130 @ref{The Feta font}.
4133 @node Modifying shapes
4134 @subsection Modifying shapes
4137 * Modifying ties and slurs::
4140 @node Modifying ties and slurs
4141 @unnumberedsubsubsec Modifying ties and slurs
4143 @cindex slurs, modifying
4144 @cindex ties, modifying
4145 @cindex Bézier curves, control points
4146 @cindex control points, Bézier curves
4148 @code{Tie}s, @code{Slur}s, @code{PhrasingSlur}s,
4149 @code{LaissezVibrerTie}s and @code{RepeatTie}s are all drawn as
4150 third-order Bézier curves. If the shape of the tie or slur which
4151 is calculated automatically is not optimum, the shape may be
4152 modified manually in two ways:
4156 by specifying the displacements to be made to the control points
4157 of the automatically calculated Bézier curve, or
4160 by explicitly specifying the positions of the four control points
4161 required to define the wanted curve.
4164 Both methods are explained below. The first method is more suitable
4165 if only slight adjustments to the curve are required; the second may
4166 be better for creating curves which are related to just a single
4169 @subsubsubheading Cubic Bézier curves
4171 Third-order or cubic Bézier curves are defined by four control
4172 points. The first and fourth control points are precisely the
4173 starting and ending points of the curve. The intermediate two
4174 control points define the shape. Animations showing how the curve
4175 is drawn can be found on the web, but the following description
4176 may be helpful. The curve starts from the first control point
4177 heading directly towards the second, gradually bending over to
4178 head towards the third and continuing to bend over to head towards
4179 the fourth, arriving there travelling directly from the third
4180 control point. The curve is entirely contained in the
4181 quadrilateral defined by the four control points. Translations,
4182 rotations and scaling of the control points all result in exactly
4183 the same operations on the curve.
4185 @subsubsubheading Specifying displacements from current control points
4187 @cindex shaping slurs and ties
4190 In this example the automatic placement of the tie is not optimum,
4191 and @code{\tieDown} would not help.
4193 @lilypond[verbatim,quote,relative=1]
4197 { r4 <g c,> <g c,> <g c,> }
4201 Adjusting the control points of the tie with @code{\shape} allows
4202 the collisions to be avoided.
4204 The syntax of @code{\shape} is
4207 [-]@code{\shape} @var{displacements} @var{item}
4210 This will reposition the control-points of @var{item} by the amounts
4211 given by @var{displacements}. The @var{displacements} argument is a
4212 list of number pairs or a list of such lists. Each element of a pair
4213 represents the displacement of one of the coordinates of a
4214 control-point. If @var{item} is a string, the result is
4215 @code{\once\override} for the specified grob type. If @var{item} is
4216 a music expression, the result is the same music expression with an
4217 appropriate tweak applied.
4219 In other words, the @code{\shape} function can act as either a
4220 @code{\once\override} command or a @code{\tweak} command depending
4221 on whether the @var{item} argument is a grob name, like @qq{Slur},
4222 or a music expression, like @qq{(}. The @var{displacements} argument
4223 specifies the displacements of the four control points as a list of
4224 four pairs of (dx . dy) values in units of staff-spaces (or a list
4225 of such lists if the curve has more than one segment).
4227 The leading hyphen is required if and only if the @code{\tweak} form
4230 So, using the same example as above and the @code{\once\override}
4231 form of @code{\shape}, this will raise the tie by half a staff-space:
4233 @lilypond[verbatim,quote,relative=1]
4236 \shape #'((0 . 0.5) (0 . 0.5) (0 . 0.5) (0 . 0.5)) Tie
4240 { r4 <g c,> <g c,> <g c,> }
4244 This positioning of the tie is better, but maybe it should be raised
4245 more in the center. The following example does this, this time using
4246 the alternative @code{\tweak} form:
4248 @lilypond[verbatim,quote,relative=1]
4251 e1-\shape #'((0 . 0.5) (0 . 1) (0 . 1) (0 . 0.5)) ~ e
4254 { r4 <g c,> <g c,> <g c,> }
4258 Changes to the horizontal positions of the control points may be made
4259 in the same way, and two different curves starting at the same
4260 musical moment may also be shaped:
4262 @lilypond[verbatim,quote,ragged-right,relative=2]
4264 \shape #'((0.7 . -0.4) (0.5 . -0.4) (0.3 . -0.3) (0 . -0.2)) Slur
4265 \shape #'((0 . 0) (0 . 0.5) (0 . 0.5) (0 . 0)) PhrasingSlur
4269 The @code{\shape} function can also displace the control points of
4270 curves which stretch across line breaks. Each piece of the broken
4271 curve can be given its own list of offsets. If changes to a
4272 particular segment are not needed, the empty list can serve as a
4273 placeholder. In this example the line break makes the single slur
4276 @lilypond[verbatim,quote,ragged-right,relative=1]
4282 Changing the shapes of the two halves of the slur makes it clearer
4283 that the slur continues over the line break:
4285 @lilypond[verbatim,quote,ragged-right,relative=1]
4286 % () may be used as a shorthand for ((0 . 0) (0 . 0) (0 . 0) (0 . 0))
4287 % if any of the segments does not need to be changed
4289 (( 0 . 0) (0 . 0) (0 . 0) (0 . 1))
4290 ((0.5 . 1.5) (1 . 0) (0 . 0) (0 . -1.5))
4297 If an S-shaped curve is required the control points must always be
4298 adjusted manually --- LilyPond will never select such shapes
4301 @lilypond[verbatim,quote,relative=2]
4302 c8( e b-> f d' a e-> g)
4303 \shape #'((0 . -1) (5.5 . -0.5) (-5.5 . -10.5) (0 . -5.5)) PhrasingSlur
4304 c8\( e b-> f d' a e-> g\)
4307 @subsubsubheading Specifying control points explicitly
4309 The coordinates of the Bézier control points are specified in units
4310 of staff-spaces. The X@tie{}coordinate is relative to the reference
4311 point of the note to which the tie or slur is attached, and the
4312 Y@tie{}coordinate is relative to the staff center line. The
4313 coordinates are specified as a list of four pairs of decimal numbers
4314 (reals). One approach is to estimate the coordinates of the two
4315 end points, and then guess the two intermediate points. The optimum
4316 values are then found by trial and error. Be aware that these values
4317 may need to be manually adjusted if any further changes are made to
4318 the music or the layout.
4320 One situation where specifying the control points explicitly is
4321 preferable to specifying displacements is when they need to be
4322 specified relative to a single note. Here is an example of this.
4323 It shows one way of indicating a slur extending into alternative
4324 sections of a volta repeat.
4326 @lilypond[verbatim,quote,relative=2]
4328 \repeat volta 3 { c4 d( e f }
4333 % create a slur and move it to a new position
4334 % the <> is just an empty chord to carry the slur termination
4335 -\tweak control-points #'((-2 . 3.8) (-1 . 3.9) (0 . 4) (1 . 3.4)) ( <> )
4340 % create a slur and move it to a new position
4341 -\tweak control-points #'((-2 . 3) (-1 . 3.1) (0 . 3.2) (1 . 2.4)) ( <> )
4348 It is not possible to modify shapes of ties or slurs by changing
4349 the @code{control-points} property if there are multiple ties or slurs
4350 at the same musical moment -- the @code{\tweak} command will also not
4351 work in this case. However, the @code{tie-configuration} property of
4352 @code{TieColumn} can be overridden to set start line and direction as
4356 Internals Reference:
4357 @rinternals{TieColumn}.
4360 @node Modifying broken spanners
4361 @subsection Modifying broken spanners
4364 * Using alterBroken::
4367 @node Using alterBroken
4368 @unnumberedsubsubsec Using @code{\alterBroken}
4370 @cindex spanners, modifying
4371 @cindex broken spanners, modifying
4372 @funindex \alterBroken
4374 When a spanner crosses a line break or breaks, each piece
4375 inherits the attributes of the original spanner. Thus, ordinary
4376 tweaking of a broken spanner applies the same modifications to
4377 each of its segments. In the example below, overriding
4378 @code{thickness} affects the slur on either side of the line
4381 @lilypond[verbatim,quote,ragged-right,relative=2]
4383 \once\override Slur.thickness = 10
4389 Independently modifying the appearance of individual pieces
4390 of a broken spanner is possible with the @code{\alterBroken}
4391 command. This command can produce either an @code{\override}
4392 or a @code{\tweak} of a spanner property.
4394 The syntax for @code{\alterBroken} is
4397 [-]@code{\alterBroken} @var{property} @var{values} @var{item}
4400 The argument @var{values} is a list of values, one for each
4401 broken piece. If @var{item} is a grob name like @code{Slur} or
4402 @code{Staff.PianoPedalBracket}, the result is an @code{\override}
4403 of the specified grob type. If @var{item} is a music expression
4404 such as @qq{(} or @qq{[} the result is the same music expression
4405 with an appropriate tweak applied.
4407 The leading hyphen must be used with the @code{\tweak} form. Do
4408 not add it when @code{\alterBroken} is used as an
4411 In its @code{\override} usage, @code{\alterBroken} may be
4412 prefaced by @code{\once} or @code{\temporary} and reverted by
4413 using @code{\revert} with @var{property}.
4415 The following code applies an independent @code{\override} to
4416 each of the slur segments in the previous example:
4418 @lilypond[verbatim,quote,ragged-right,relative=2]
4420 \alterBroken thickness #'(10 1) Slur
4426 The @code{\alterBroken} command may be used with any spanner
4427 object, including @code{Tie}, @code{PhrasingSlur}, @code{Beam}
4428 and @code{TextSpanner}. For example, an editor preparing a
4429 scholarly edition may wish to indicate the absence of part of a
4430 phrasing slur in a source by dashing only the segment which has
4431 been added. The following example illustrates how this can be
4432 done, in this case using the @code{\tweak} form of the command:
4434 @lilypond[verbatim,quote,ragged-right,relative=2]
4435 % The empty list is conveniently used below, because it is the
4436 % default setting of dash-definition, resulting in a solid curve.
4437 c2-\alterBroken dash-definition #'(() ((0 1.0 0.4 0.75))) \(e
4442 It is important to understand that @code{\alterBroken} will set
4443 each piece of a broken spanner to the corresponding value in
4444 @var{values}. When there are fewer values than pieces, any
4445 additional piece will be assigned the empty list. This may lead
4446 to undesired results if the layout property is not set to the
4447 empty list by default. In such cases, each segment should be
4448 assigned an appropriate value.
4451 Line breaks may occur in different places following changes in
4452 layout. Settings chosen for @code{\alterBroken} may be unsuitable
4453 for a spanner that is no longer broken or is split into more
4454 segments than before. Explicit use of @code{\break} can guard
4455 against this situation.
4457 The @code{\alterBroken} command is ineffective for spanner
4458 properties accessed before line-breaking such as
4463 @rextend{Difficult tweaks}.
4466 @node Unpure-pure containers
4467 @subsection Unpure-pure containers
4469 @cindex Scheme, pure containers
4470 @cindex Scheme, unpure containers
4471 @cindex pure containers, Scheme
4472 @cindex unpure containers, Scheme
4473 @cindex horizontal spacing, overriding
4475 Unpure-pure containers are useful for overriding @emph{Y-axis} spacing
4476 calculations - specifically @code{Y-offset} and @code{Y-extent} - with a
4477 Scheme function instead of a literal (i.e. a number or pair).
4479 For certain grobs, the @code{Y-extent} is based on the @code{stencil}
4480 property, overriding the stencil property of one of these will
4481 require an additional @code{Y-extent} override with an unpure-pure
4482 container. When a function overrides a @code{Y-offset} and/or
4483 @code{Y-extent} it is assumed that this will trigger line breaking
4484 calculations too early during compilation. So the function is not
4485 evaluated at all (usually returning a value of @samp{0} or
4486 @samp{'(0 . 0)}) which can result in collisions. A @q{pure} function
4487 will not affect properties, objects or grob suicides and therefore will
4488 always have its Y-axis-related evaluated correctly.
4490 Currently, there are about thirty functions that are already considered
4491 @q{pure} and Unpure-pure containers are a way to set functions not on
4492 this list as @q{pure}. The @q{pure} function is evaluated @emph{before}
4493 any line-breaking and so the horizontal spacing can be adjusted
4494 @q{in time}. The @q{unpure} function is then evaluated @emph{after}
4497 @warning{As it is difficult to always know which functions are on this
4498 list we recommend that any @q{pure} functions you create do not use
4499 @code{Beam} or @code{VerticalAlignment} grobs.}
4501 An unpure-pure container is constructed as follows;
4503 @code{(ly:make-unpure-pure-container f0 f1)}
4505 where @code{f0} is a function taking @var{n} arguments (@var{n >= 1})
4506 and the first argument must always be the grob. This is the function
4507 that gives the actual result. @var{f1} is the function being labeled
4508 as @q{pure} that takes @var{n + 2} arguments. Again, the first argument
4509 must always still be the grob but the second and third are @q{start}
4510 and @q{end} arguments.
4512 @var{start} and @var{end} are, for all intents and purposes, dummy
4513 values that only matter for @code{Spanners} (i.e @code{Hairpin} or
4514 @code{Beam}), that can return different height estimations based on a
4515 starting and ending column.
4517 The rest are the other arguments to the first function (which
4518 may be none if @var{n = 1}).
4520 The results of the second function are used as an approximation of the
4521 value needed which is then used by the first function to get the real
4522 value which is then used for fine-tuning much later during the spacing
4525 @lilypond[verbatim,quote,ragged-right]
4526 #(define (square-line-circle-space grob)
4527 (let* ((pitch (ly:event-property (ly:grob-property grob 'cause) 'pitch))
4528 (notename (ly:pitch-notename pitch)))
4529 (if (= 0 (modulo notename 2))
4530 (make-circle-stencil 0.5 0.0 #t)
4531 (make-filled-box-stencil '(0 . 1.0)
4534 squareLineCircleSpace = {
4535 \override NoteHead.stencil = #square-line-circle-space
4538 smartSquareLineCircleSpace = {
4539 \squareLineCircleSpace
4540 \override NoteHead.Y-extent =
4541 #(ly:make-unpure-pure-container
4542 ly:grob::stencil-height
4543 (lambda (grob start end) (ly:grob::stencil-height grob)))
4546 \new Voice \with { \remove "Stem_engraver" }
4548 \squareLineCircleSpace
4550 \smartSquareLineCircleSpace
4555 In the first measure, without the unpure-pure container, the spacing
4556 engine does not know the width of the note head and lets it collide with
4557 the accidentals. In the second measure, with unpure-pure containers,
4558 the spacing engine knows the width of the note heads and avoids the
4559 collision by lengthening the line accordingly.
4561 Usually for simple calculations nearly-identical functions for both the
4562 @q{unpure} and @q{pure} parts can be used, by only changing the number
4563 of arguments passed to, and the scope of, the function.
4565 @warning{If a function is labeled as @q{pure} and it turns out not to
4566 be, the results can be unexpected.}
4569 @node Using music functions
4570 @section Using music functions
4572 @c TODO -- add @seealso, etc. to these subsections
4574 Where tweaks need to be reused with different music expressions,
4575 it is often convenient to make the tweak part of a @emph{music
4576 function}. In this section, we discuss only @emph{substitution}
4577 functions, where the object is to substitute a variable into a
4578 piece of LilyPond input code. Other more complex functions are
4579 described in @rextend{Music functions}.
4582 * Substitution function syntax::
4583 * Substitution function examples::
4586 @node Substitution function syntax
4587 @subsection Substitution function syntax
4589 Making a function that substitutes a variable into LilyPond
4590 code is easy. The general form of these functions is
4594 #(define-music-function
4595 (parser location @var{arg1} @var{arg2} @dots{})
4596 (@var{type1?} @var{type2?} @dots{})
4598 @var{@dots{}music@dots{}}
4605 @multitable @columnfractions .33 .66
4606 @item @code{@var{argN}}
4607 @tab @var{n}th argument
4609 @item @code{@var{typeN?}}
4610 @tab a scheme @emph{type predicate} for which @code{@var{argN}}
4611 must return @code{#t}.
4613 @item @code{@var{@dots{}music@dots{}}}
4614 @tab normal LilyPond input, using @code{$} (in places where only
4615 Lilypond constructs are allowed) or @code{#} (to use it as a Scheme
4616 value or music function argument or music inside of music lists) to
4621 The @code{parser} and @code{location} arguments are mandatory, and
4622 are used in some advanced situations as described in the
4623 @q{Extending} manual (see @rextend{Music functions}). For
4624 substitution functions, just be sure to include them.
4626 The list of type predicates is also required. Some of the most
4627 common type predicates used in music functions are:
4631 cheap-list? @emph{(use instead of }@q{list?}@emph{ for faster processing)}
4643 For a list of available type predicates, see
4644 @ref{Predefined type predicates}. User-defined type predicates
4649 @ref{Predefined type predicates}.
4652 @rextend{Music functions}.
4655 @file{lily/music-scheme.cc},
4657 @file{scm/lily.scm}.
4660 @node Substitution function examples
4661 @subsection Substitution function examples
4663 This section introduces some substitution function examples.
4664 These are not intended to be exhaustive, but rather to demonstrate
4665 some of the possibilities of simple substitution functions.
4667 In the first example, a function is defined that simplifies
4668 setting the padding of a TextScript:
4670 @lilypond[quote,verbatim,ragged-right]
4672 #(define-music-function
4673 (parser location padding)
4676 \once \override TextScript.padding = #padding
4680 c4^"piu mosso" b a b
4682 c4^"piu mosso" b a b
4684 c4^"piu mosso" b a b
4688 In addition to numbers, we can use music expressions such
4689 as notes for arguments to music functions:
4691 @lilypond[quote,verbatim,ragged-right]
4693 #(define-music-function
4694 (parser location note)
4697 \tweak NoteHead.stencil #ly:text-interface::print
4698 \tweak NoteHead.text
4699 \markup \musicglyph #"custodes.mensural.u0"
4700 \tweak Stem.stencil ##f
4704 \relative c' { c4 d e f \custosNote g }
4707 Substitution functions with multiple arguments can be defined:
4709 @lilypond[quote,verbatim,ragged-right]
4711 #(define-music-function
4712 (parser location padding tempotext)
4715 \once \override Score.MetronomeMark.padding = #padding
4716 \tempo \markup { \bold #tempotext }
4720 \tempo \markup { "Low tempo" }
4722 \tempoPadded #4.0 "High tempo"
4727 @c TODO: add appropriate @@ref's here.