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13 @node Changing defaults
14 @chapter Changing defaults
16 The purpose of LilyPond's design is to provide the finest quality
17 output by default. Nevertheless, it may happen that you need to
18 change this default layout. The layout is controlled through a large
19 number of @q{knobs and switches} collectively called @q{properties}.
20 A tutorial introduction to accessing and modifying these properties
21 can be found in the Learning Manual, see @rlearning{Tweaking output}.
22 This should be read first. This chapter covers similar ground, but
23 in a style more appropriate to a reference manual.
25 @cindex Internals Reference
27 The definitive description of the controls available for tuning can
28 be found in a separate document: @rinternalsnamed{Top,the Internals
29 Reference}. That manual lists all the variables, functions and
30 options available in LilyPond. It is written as a HTML document,
32 @c leave the @uref as one long line.
33 @uref{http://@/lilypond@/.org/@/doc/@/stable/@/Documentation/@/internals/,on@/-line},
34 and is also included with the LilyPond documentation package.
36 Internally, LilyPond uses Scheme (a LISP dialect) to provide
37 infrastructure. Overriding layout decisions in effect accesses the
38 program internals, which requires Scheme input. Scheme elements are
39 introduced in a @file{.ly} file with the hash
40 mark@tie{}@code{#}.@footnote{@rextend{Scheme tutorial}, contains a
41 short tutorial on entering numbers, lists, strings, and symbols in
46 * Interpretation contexts::
47 * Explaining the Internals Reference::
48 * Modifying properties::
49 * Useful concepts and properties::
51 * Using music functions::
55 @node Interpretation contexts
56 @section Interpretation contexts
58 This section describes what contexts are, and how to modify them.
61 * Contexts explained::
62 * Creating and referencing contexts::
63 * Keeping contexts alive::
64 * Modifying context plug-ins::
65 * Changing context default settings::
66 * Defining new contexts::
67 * Context layout order::
72 @rlearning{Contexts and engravers}.
75 @file{ly/engraver-init.ly},
76 @file{ly/performer-init.ly}.
79 @rlsr{Contexts and engravers}.
82 @rinternals{Contexts},
83 @rinternals{Engravers and Performers}.
86 @node Contexts explained
87 @subsection Contexts explained
90 @c TODO Rethink and rewrite
92 >> > > - list of contexts: my *danger unmaintainable*
93 >> > > alarm just went off. I'm
95 I knew it would... And leaving out some of them is perfectly fine
97 I do think that a list like this, with the main contexts and a
99 description of what they do (perhaps also with a note about what
101 behavior is associated with each of them, but this may be
103 should be there, and then we could simply list the remaining ones
105 further explanation and with links to the IR.
108 @c TODO Improve layout, order and consistency of wording -td
110 @c TODO Add introduction which explains contexts in generality -td
112 @c TODO Describe propagation of property values -td
114 Contexts are arranged hierarchically:
117 * Output definitions - blueprints for contexts::
118 * Score - the master of all contexts::
119 * Top-level contexts - staff containers::
120 * Intermediate-level contexts - staves::
121 * Bottom-level contexts - voices::
124 @node Output definitions - blueprints for contexts
125 @unnumberedsubsubsec Output definitions - blueprints for contexts
127 This section explains the relevance of output definitions when
128 working with contexts. Examples for actual output definitions are
129 given later (see @ref{Changing all contexts of the same type}).
131 @cindex output definitions
133 While music written in a file may refer to context types and
134 names, contexts are created only when the music is actually being
135 interpreted. LilyPond interprets music under control of an
136 @q{output definition} and may do so for several different output
137 definitions, resulting in different output. The output definition
138 relevant for printing music is specified using @code{\layout}.
141 A much simpler output definition used for producing Midi output is
142 specified using @code{\midi}. Several other output definitions
143 are used by LilyPond internally, like when using the part combiner
144 (@ref{Automatic part combining}) or creating music quotes
145 (@ref{Quoting other voices}).
147 Output definitions define the relation between contexts as well as
148 their respective default settings. While most changes will
149 usually be made inside of a @code{\layout} block, Midi-related
150 settings will only have an effect when made within a @code{\midi}
153 @funindex autoBeaming
154 Some settings affect several outputs: for example, if
155 @code{autoBeaming} is turned off in some context, beams count as
156 melismata for the purpose of matching music to lyrics as described
157 in @ref{Automatic syllable durations}. This matching is done both
158 for printed output as well as for Midi. If changes made to
159 @code{autoBeaming} within a context definition of a @code{\layout}
160 block are not repeated in the corresponding @code{\midi} block,
161 lyrics and music will get out of sync in Midi.
165 @file{ly/engraver-init.ly}.
166 @file{ly/performer-init.ly}.
168 @node Score - the master of all contexts
169 @unnumberedsubsubsec Score - the master of all contexts
171 This is the top level notation context. No other context can
172 contain a Score context. By default the Score context handles
173 the administration of time signatures and makes sure that items
174 such as clefs, time signatures, and key-signatures are aligned
177 A Score context is instantiated implicitly when a
178 @code{\score @{@dots{}@}} block is processed.
180 @node Top-level contexts - staff containers
181 @unnumberedsubsubsec Top-level contexts - staff containers
183 @strong{@emph{StaffGroup}}
185 Groups staves while adding a bracket on the left side, grouping
186 the staves together. The bar lines of the contained staves are
187 connected vertically. @code{StaffGroup} only consists of a collection
188 of staves, with a bracket in front and spanning bar lines.
190 @strong{@emph{ChoirStaff}}
192 Identical to @code{StaffGroup} except that the bar lines of the
193 contained staves are not connected vertically.
195 @strong{@emph{GrandStaff}}
197 A group of staves, with a brace on the left side, grouping the
198 staves together. The bar lines of the contained staves are
199 connected vertically.
201 @strong{@emph{PianoStaff}}
203 Just like @code{GrandStaff}, but with support for instrument names
204 to the left of each system.
206 @node Intermediate-level contexts - staves
207 @unnumberedsubsubsec Intermediate-level contexts - staves
209 @strong{@emph{Staff}}
211 Handles clefs, bar lines, keys, accidentals. It can contain
212 @code{Voice} contexts.
214 @strong{@emph{RhythmicStaff}}
216 Like @code{Staff} but for printing rhythms. Pitches are ignored
217 when engraving; the notes are printed on one line. The MIDI
218 rendition retains pitches unchanged.
220 @strong{@emph{TabStaff}}
222 Context for generating tablature. By default lays the music
223 expression out as a guitar tablature, printed on six lines.
225 @strong{@emph{DrumStaff}}
227 Handles typesetting for percussion. Can contain @code{DrumVoice}
229 @strong{@emph{VaticanaStaff}}
231 Same as @code{Staff}, except that it is designed for typesetting
232 a piece in gregorian style.
234 @strong{@emph{MensuralStaff}}
236 Same as @code{Staff}, except that it is designed for typesetting
237 a piece in mensural style.
239 @node Bottom-level contexts - voices
240 @unnumberedsubsubsec Bottom-level contexts - voices
242 Voice-level contexts initialise certain properties and start
243 appropriate engravers. A bottom-level context is one without
244 @code{defaultchild}. While it is possible to let it
245 accept/@/contain subcontexts, they can only be created and entered
248 @strong{@emph{Voice}}
250 Corresponds to a voice on a staff. This context handles the
251 conversion of dynamic signs, stems, beams, super- and sub-scripts,
252 slurs, ties, and rests. You have to instantiate this explicitly
253 if you require multiple voices on the same staff.
255 @strong{@emph{VaticanaVoice}}
257 Same as @code{Voice}, except that it is designed for typesetting
258 a piece in gregorian style.
260 @strong{@emph{MensuralVoice}}
262 Same as @code{Voice}, with modifications for typesetting a piece in
265 @strong{@emph{Lyrics}}
267 Corresponds to a voice with lyrics. Handles the printing of a
268 single line of lyrics.
270 @strong{@emph{DrumVoice}}
272 The voice context used in a percussion staff.
274 @strong{@emph{FiguredBass}}
276 The context in which @code{BassFigure} objects are created from
277 input entered in @code{\figuremode} mode.
279 @strong{@emph{TabVoice}}
281 The voice context used within a @code{TabStaff} context. Usually
282 left to be created implicitly.
284 @strong{@emph{CueVoice}}
286 A voice context used to render notes of a reduced size, intended
287 primarily for adding cue notes to a staff, see @ref{Formatting
288 cue notes}. Usually left to be created implicitly.
290 @strong{@emph{ChordNames}}
292 Typesets chord names.
297 Then the following, which I don't know what to do with:
299 * GregorianTranscriptionVoice
300 * GregorianTranscriptionStaff
303 Engraves fretboards from chords. Not easy... Not
305 There is now some documentation on FretBoards in the NR, under
306 instrument-specific notation -- cds.
311 Hard coded entry point for LilyPond. Cannot be tuned.
313 Silently discards all musical information given to this
318 @node Creating and referencing contexts
319 @subsection Creating and referencing contexts
324 @cindex referencing contexts
325 @cindex Contexts, creating and referencing
327 LilyPond will create lower-level contexts automatically if a music
328 expression is encountered before a suitable context exists, but this
329 is usually successful only for simple scores or music fragments like
330 the ones in the documentation. For more complex scores it is
331 advisable to specify all contexts explicitly with either the
332 @code{\new} or @code{\context} command. The syntax of
333 these two commands is very similar:
336 [\new | \context] @var{Context} [ = @var{name}] [@var{music-expression}]
340 where either @code{\new} or @code{\context} may be specified.
341 @var{Context} is the type of context which is to be created,
342 @var{name} is an optional name to be given to the particular context
343 being created and @var{music-expression} is a single music expression
344 that is to be interpreted by the engravers and performers in this
347 The @code{\new} prefix without a name is commonly used to create
348 scores with many staves:
350 @lilypond[quote,verbatim]
352 \new Staff \relative {
353 % leave the Voice context to be created implicitly
356 \new Staff \relative {
363 and to place several voices into one staff:
365 @lilypond[quote,verbatim]
367 \new Voice \relative {
371 \new Voice \relative {
379 @code{\new} should always be used to specify unnamed contexts.
381 The difference between @code{\new} and @code{\context} is in the
386 @code{\new} with or without a name will always create a fresh,
387 distinct, context, even if one with the same name already exists:
389 @lilypond[quote,verbatim]
391 \new Voice = "A" \relative {
395 \new Voice = "A" \relative {
403 @code{\context} with a name specified will create a distinct context
404 only if a context of the same type with the same name in the same
405 context hierarchy does not already exist. Otherwise it will be taken
406 as a reference to that previously created context, and its music
407 expression will be passed to that context for interpretation.
409 One application of named contexts is in separating the score layout
410 from the musical content. Either of these two forms is valid:
412 @lilypond[quote,verbatim]
426 \context Voice = "one" {
431 \context Voice = "two" {
440 @lilypond[quote,verbatim]
445 \context Voice = "one" {
448 \context Voice = "two" {
454 \context Voice = "one" {
459 \context Voice = "two" {
469 Alternatively, variables may be employed to similar effect. See
470 @rlearning{Organizing pieces with variables}.
473 @code{\context} with no name will match the first of any previously
474 created contexts of the same type in the same context heirarchy,
475 even one that has been given a name, and its music expression will be
476 passed to that context for interpretation. This form is rarely
477 useful. However, @code{\context} with no name and no music expression
478 is used to set the context in which a Scheme procedure specified with
479 @code{\applyContext} is executed:
482 \new Staff \relative @{
485 \applyContext #(lambda (ctx)
487 (display (ly:context-current-moment ctx)))
494 A context must be named if it is to be referenced later, for example
495 when lyrics are associated with music:
498 \new Voice = "tenor" @var{music}
500 \new Lyrics \lyricsto "tenor" @var{lyrics}
504 For details of associating lyrics with music see
505 @ref{Automatic syllable durations}.
507 The properties of all contexts of a particular type can be modified
508 in a @code{\layout} block (with a different syntax), see
509 @ref{Changing all contexts of the same type}. This construct also
510 provides a means of keeping layout instructions separate from the
511 musical content. If a single context is to be modified, a @code{\with}
512 block must be used, see @ref{Changing just one specific context}.
516 @rlearning{Organizing pieces with variables}.
519 @ref{Changing just one specific context},
520 @ref{Automatic syllable durations}.
523 @node Keeping contexts alive
524 @subsection Keeping contexts alive
526 @cindex contexts, keeping alive
527 @cindex contexts, lifetime
529 Contexts are usually terminated at the first musical moment in
530 which they have nothing to do. So @code{Voice} contexts die as
531 soon as they contain no events; @code{Staff} contexts die as soon
532 as all the @code{Voice} contexts within them contain no events; etc.
533 This can cause difficulties if earlier contexts which have died
534 have to be referenced, for example, when changing staves with
535 @code{\change} commands, associating lyrics with a voice with
536 @code{\lyricsto} commands, or when adding further musical events to
539 There is an exception to this general rule: inside of an
540 @code{@{@dots{}@}} construct (sequential music), the construct's
541 notion of the ``current context'' will descend whenever an element
542 of the sequence ends in a subcontext of the previous current
543 context. This avoids spurious creation of implicit contexts in a
544 number of situations but means that the first context descended
545 into will be kept alive until the end of the expression.
547 In contrast, the contexts of a @code{<<@dots{}>>} construct's
548 (simultaneous music) expression are not carried forth, so
549 enclosing a context creating command in an extra pair of
550 @code{<<@dots{}>>} will keep the context from persisting through
551 all of the enclosing @code{@{@dots{}@}} sequence.
553 Any context can be kept alive by ensuring it has something to do at
554 every musical moment. @code{Staff} contexts are kept alive by
555 ensuring one of their voices is kept alive. One way of doing this
556 is to add spacer rests to a voice in parallel with the real music.
557 These need to be added to every @code{Voice} context which needs to
558 be kept alive. If several voices are to be used sporadically it is
559 safest to keep them all alive rather than attempting to rely on the
560 exceptions mentioned above.
562 In the following example, both voice A and voice B are kept alive
563 in this way for the duration of the piece:
565 @lilypond[quote,verbatim]
566 musicA = \relative { d''4 d d d }
567 musicB = \relative { g'4 g g g }
570 \new Voice = "A" { s1*5 } % Keep Voice "A" alive for 5 bars
571 \new Voice = "B" { s1*5 } % Keep Voice "B" alive for 5 bars
576 \context Voice = "A" {
580 \context Voice = "B" {
584 \context Voice = "A" { \musicA }
585 \context Voice = "B" { \musicB }
586 \context Voice = "A" { \musicA }
597 @cindex lyrics, aligning with sporadic melody
599 The following example shows how a sporadic melody line with lyrics
600 might be written using this approach. In a real situation the
601 melody and accompaniment would consist of several different
604 @lilypond[quote,verbatim]
605 melody = \relative { a'4 a a a }
606 accompaniment = \relative { d'4 d d d }
607 words = \lyricmode { These words fol -- low the mel -- o -- dy }
610 \new Staff = "music" {
612 \new Voice = "melody" {
614 s1*4 % Keep Voice "melody" alive for 4 bars
617 \new Voice = "accompaniment" {
622 \context Voice = "melody" { \melody }
623 \context Voice = "accompaniment" { \accompaniment }
625 \context Voice = "accompaniment" { \accompaniment }
627 \context Voice = "melody" { \melody }
628 \context Voice = "accompaniment" { \accompaniment }
633 \new Lyrics \with { alignAboveContext = #"music" }
634 \lyricsto "melody" { \words }
639 An alternative way, which may be better in many circumstances, is
640 to keep the melody line alive by simply including spacer notes to
641 line it up correctly with the accompaniment:
643 @lilypond[quote,verbatim]
650 accompaniment = \relative {
656 words = \lyricmode { These words fol -- low the mel -- o -- dy }
660 \new Staff = "music" {
662 \new Voice = "melody" {
666 \new Voice = "accompaniment" {
672 \new Lyrics \with { alignAboveContext = #"music" }
673 \lyricsto "melody" { \words }
679 @node Modifying context plug-ins
680 @subsection Modifying context plug-ins
682 @c TODO Should this be Modifying engravers or Modifying contexts?
684 Notation contexts (like @code{Score} and @code{Staff}) not only store
685 properties, they also contain plug-ins called @q{engravers} that create
686 notation elements. For example, the @code{Voice} context contains a
687 @code{Note_heads_engraver} and the @code{Staff} context contains a
690 For a full a description of each plug-in, see
692 @rinternals{Engravers and Performers}.
695 Internals Reference @expansion{} Translation @expansion{} Engravers.
697 Every context described in
699 @rinternals{Contexts}
702 Internals Reference @expansion{} Translation @expansion{} Context.
704 lists the engravers used for that context.
707 It can be useful to shuffle around these plug-ins. This is done by
708 starting a new context with @code{\new} or @code{\context}, and
714 \new @var{context} \with @{
722 @emph{@dots{}music@dots{}}
727 where the @dots{} should be the name of an engraver. Here is a simple
728 example which removes @code{Time_signature_engraver} and
729 @code{Clef_engraver} from a @code{Staff} context,
731 @lilypond[quote,verbatim]
733 \new Staff \relative {
737 \remove "Time_signature_engraver"
738 \remove "Clef_engraver"
745 In the second staff there are no time signature or clef symbols. This
746 is a rather crude method of making objects disappear since it will affect
747 the entire staff. This method also influences the spacing, which may or
748 may not be desirable. More sophisticated methods of blanking objects
749 are shown in @rlearning{Visibility and color of objects}.
751 The next example shows a practical application. Bar lines and time
752 signatures are normally synchronized across the score. This is done
753 by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
754 This plug-in keeps an administration of time signature, location
755 within the measure, etc. By moving these engraver from @code{Score} to
756 @code{Staff} context, we can have a score where each staff has its own
759 @cindex polymetric scores
760 @cindex time signature, multiple
762 @lilypond[quote,verbatim]
766 \consists "Timing_translator"
767 \consists "Default_bar_line_engraver"
774 \consists "Timing_translator"
775 \consists "Default_bar_line_engraver"
785 \remove "Timing_translator"
786 \remove "Default_bar_line_engraver"
794 The order in which the engravers are specified is the order in
795 which they are called to carry out their processing. Usually the
796 order in which the engravers are specified does not matter, but in
797 a few special cases the order is important, for example where one
798 engraver writes a property and another reads it, or where one
799 engraver creates a grob and another must process it.
801 The following orderings are important:
805 the @code{Bar_engraver} must normally be first,
808 the @code{New_fingering_engraver} must come before the
809 @code{Script_column_engraver},
812 the @code{Timing_translator} must come before the
813 @code{Bar_number_engraver}.
819 @file{ly/engraver-init.ly}.
822 @node Changing context default settings
823 @subsection Changing context default settings
825 @cindex default context properties, changing
826 @cindex context properties, changing defaults
828 Context and grob properties can be changed with @code{\set}
829 and @code{\override} commands, as described in
830 @ref{Modifying properties}. These commands create music events,
831 making the changes take effect at the point in time the music
834 In contrast, this section explains how to change the @emph{default}
835 values of context and grob properties at the time the context is
836 created. There are two ways of doing this. One modifies the default
837 values in all contexts of a particular type, the other modifies the
838 default values in just one particular instance of a context.
841 * Changing all contexts of the same type::
842 * Changing just one specific context::
843 * Order of precedence::
846 @node Changing all contexts of the same type
847 @unnumberedsubsubsec Changing all contexts of the same type
849 @cindex \context in \layout block
853 The default context settings which are to be used for typesetting in
854 @code{Score}, @code{Staff}, @code{Voice} and other contexts may be
855 specified in a @code{\context} block within any @code{\layout}
858 Settings for Midi output as opposed to typesetting will have to be
859 separately specified in @code{\midi} blocks (see @ref{Output
860 definitions - blueprints for contexts}).
862 The @code{\layout} block should be placed within the @code{\score}
863 block to which it is to apply, after the music.
869 [context settings for all Voice contexts]
873 [context settings for all Staff contexts]
878 The following types of settings may be specified:
882 An @code{\override} command, but with the context name omitted
884 @lilypond[quote,verbatim]
887 a'4^"Thicker stems" a a a
893 \override Stem.thickness = #4.0
900 Directly setting a context property
902 @lilypond[quote,verbatim]
905 a'4^"Smaller font" a a a
918 A predefined command such as @code{\dynamicUp} or a music
919 expression like @code{\accidentalStyle dodecaphonic}
921 @lilypond[quote,verbatim]
924 a'4^"Dynamics above" a a a
934 \accidentalStyle dodecaphonic
941 A user-defined variable containing a @code{\with} block; for details
942 of the @code{\with} block see
943 @ref{Changing just one specific context}.
945 @lilypond[quote,verbatim]
946 StaffDefaults = \with {
953 a'4^"Smaller font" a a a
968 Property-setting commands can be placed in a @code{\layout} block
969 without being enclosed in a @code{\context} block. Such settings
970 are equivalent to including the same property-setting commands at
971 the start of every context of the type specified. If no context
972 is specified @emph{every} bottom-level context is affected, see
973 @ref{Bottom-level contexts - voices}. The syntax of a
974 property-setting command in a @code{\layout} block is the same as
975 the same command written in the music stream.
977 @lilypond[quote,verbatim]
981 a'4^"Smaller font" a a a
986 \accidentalStyle dodecaphonic
988 \override Voice.Stem.thickness = #4.0
994 @node Changing just one specific context
995 @unnumberedsubsubsec Changing just one specific context
1000 The context properties of just one specific context instance can be
1001 changed in a @code{\with} block. All other context instances of the
1002 same type retain the default settings built into LilyPond and modified
1003 by any @code{\layout} block within scope. The @code{\with} block
1004 must be placed immediately after the @code{\new} @var{context-type}
1008 \new Staff \with @{ [context settings for this context instance only] @}
1014 Since such a @q{context modification} is specified inside of
1015 music, it will affect @emph{all} outputs (typesetting @emph{and}
1016 Midi) as opposed to changes within an output definition.
1018 The following types of settings may be specified:
1022 An @code{\override} command, but with the context name omitted
1024 @lilypond[quote,verbatim]
1027 \new Voice \with { \override Stem.thickness = #4.0 }
1030 a'4^"Thick stems" a a a
1039 Directly setting a context property
1041 @lilypond[quote,verbatim]
1046 a'4^"Default font" a a a
1050 \new Staff \with { fontSize = #-4 }
1053 a'4^"Smaller font" a a a
1062 A predefined command such as @code{\dynamicUp}
1064 @lilypond[quote,verbatim]
1070 a'4^"Dynamics below" a a a
1075 \new Staff \with { \accidentalStyle dodecaphonic }
1077 \new Voice \with { \dynamicUp }
1080 a'4^"Dynamics above" a a a
1091 @node Order of precedence
1092 @unnumberedsubsubsec Order of precedence
1094 The value of a property which applies at a particular time is
1095 determined as follows:
1099 if an @code{\override} or @code{\set} command in the input stream is
1100 in effect that value is used,
1103 otherwise the default value taken from a @code{\with} statement
1104 on the context initiation statement is used,
1107 otherwise the default value taken from the most recent appropriate
1108 @code{\context} block in the @code{\layout} or @code{\midi} blocks
1112 otherwise the LilyPond built-in default is used.
1117 @rlearning{Modifying context properties}.
1120 @ref{Contexts explained},
1121 @ref{Bottom-level contexts - voices},
1122 @ref{The set command},
1123 @ref{The override command},
1124 @ref{The layout block,,The @code{@bs{}layout} block}.
1127 @node Defining new contexts
1128 @subsection Defining new contexts
1130 @cindex contexts, defining new
1131 @cindex engravers, including in contexts
1146 Specific contexts, like @code{Staff} and @code{Voice}, are made from
1147 simple building blocks. It is possible to create new types of
1148 contexts with different combinations of engraver plug-ins.
1150 The next example shows how to build a different type of
1151 @code{Voice} context from scratch. It will be similar to
1152 @code{Voice}, but only prints centered slash note heads. It can be used
1153 to indicate improvisation in jazz pieces,
1155 @lilypond[quote,ragged-right]
1156 \layout { \context {
1158 \type "Engraver_group"
1159 \consists "Note_heads_engraver"
1160 \consists "Rhythmic_column_engraver"
1161 \consists "Text_engraver"
1162 \consists "Pitch_squash_engraver"
1163 squashedPosition = #0
1164 \override NoteHead.style = #'slash
1169 \accepts "ImproVoice"
1173 a'4 d8 bes8 \new ImproVoice { c4^"ad lib" c
1174 c4 c^"undress" c_"while playing :)" c }
1180 These settings are defined within a @code{\context} block inside a
1181 @code{\layout} block,
1191 In the following discussion, the example input shown should go in place
1192 of the @dots{} in the previous fragment.
1194 First it is necessary to define a name for the new context:
1200 Since it is similar to the @code{Voice} context, we want commands that
1201 work in (existing) @code{Voice} contexts to continue working. This is
1202 achieved by giving the new context an alias of @code{Voice},
1208 The context will print notes and instructive texts, so we need to add
1209 the engravers which provide this functionality, plus the engraver which
1210 groups notes, stems and rests which occur at the same musical moment
1214 \consists "Note_heads_engraver"
1215 \consists "Text_engraver"
1216 \consists "Rhythmic_column_engraver"
1219 The note heads should all be placed on the center line,
1222 \consists "Pitch_squash_engraver"
1223 squashedPosition = #0
1226 The @code{Pitch_squash_engraver} modifies note heads (created
1227 by the @code{Note_heads_engraver}) and sets their vertical
1228 position to the value of @code{squashedPosition}, in this
1229 case@tie{}@code{0}, the center line.
1231 The notes look like a slash, and have no stem,
1234 \override NoteHead.style = #'slash
1238 All these plug-ins have to communicate under the control of the
1239 context. The mechanisms with which contexts communicate are
1240 established by declaring the context @code{\type}. Within a
1241 @code{\layout} block, most contexts will be of type
1242 @code{Engraver_group}. Some special contexts and contexts in
1243 @code{\midi} blocks use other context types. Copying and
1244 modifying an existing context definition will also fill in the
1245 type. Since this example creates a definition from scratch, it
1246 needs to be specified explicitly.
1249 \type "Engraver_group"
1252 Put together, we get
1257 \type "Engraver_group"
1258 \consists "Note_heads_engraver"
1259 \consists "Text_engraver"
1260 \consists "Rhythmic_column_engraver"
1261 \consists "Pitch_squash_engraver"
1262 squashedPosition = #0
1263 \override NoteHead.style = #'slash
1270 Contexts form hierarchies. We want to place the @code{ImproVoice}
1271 context within the @code{Staff} context, just like normal @code{Voice}
1272 contexts. Therefore, we modify the @code{Staff} definition with the
1273 @code{\accepts} command,
1282 @funindex \inherit-acceptability
1283 Often when reusing an existing context definition, the resulting
1284 context can be used anywhere where the original context would have
1290 \inherit-acceptability @var{to} @var{from}
1295 will arrange to have contexts of type @var{to} accepted by all
1296 contexts also accepting @var{from}. For example, using
1301 \inherit-acceptability "ImproVoice" "Voice"
1306 will add an @code{\accepts} for @code{ImproVoice} to both
1307 @code{Staff} and @code{RhythmicStaff} definitions.
1310 The opposite of @code{\accepts} is @code{\denies},
1311 which is sometimes needed when reusing existing context definitions.
1313 Arranging the required pieces into a @code{\layout} block leaves
1322 \inherit-acceptability "ImproVoice" "Voice"
1326 Then the output at the start of this subsection can be entered as
1334 c c_"while playing :)"
1340 To complete this example, changes affecting the context hierarchy
1341 should be repeated in a @code{\midi} block so that Midi output
1342 depends on the same context relations.
1346 Internals Reference:
1347 @rinternals{Note_heads_engraver},
1348 @rinternals{Text_engraver},
1349 @rinternals{Rhythmic_column_engraver},
1350 @rinternals{Pitch_squash_engraver}.
1353 @node Context layout order
1354 @subsection Context layout order
1356 @cindex contexts, layout order
1360 Contexts are normally positioned in a system from top to bottom
1361 in the order in which they are encountered in the input file. When
1362 contexts are nested, the outer context will include inner nested
1363 contexts as specified in the input file, provided the inner contexts
1364 are included in the outer context's @qq{accepts} list. Nested
1365 contexts which are not included in the outer context's @qq{accepts}
1366 list will be repositioned below the outer context rather than nested
1369 The @qq{accepts} list of a context can be changed with the
1370 @code{\accepts} or @code{\denies} commands. @code{\accepts} adds a
1371 context to the @qq{accepts} list and @code{\denies} removes a context
1374 For example, a square-braced staff group is not usually found within a
1375 curved-braced staff with connecting staff bars, and a @code{GrandStaff}
1376 does not accept a @code{StaffGroup} inside it by default.
1378 @lilypond[verbatim,quote]
1385 \new Staff { \set Staff.instrumentName = bottom f'1 }
1390 However, by using the @code{\accepts} command, @code{StaffGroup} can be
1391 added to the @code{GrandStaff} context:
1393 @lilypond[verbatim,quote]
1400 \new Staff { \set Staff.instrumentName = bottom f'1 }
1405 \accepts "StaffGroup"
1411 @code{\denies} is mainly used when a new context is being based on
1412 another, but the required nesting differs. For example, the
1413 @code{VaticanaStaff} context is based on the @code{Staff} context, but
1414 with the @code{VaticanaVoice} context substituted for the @code{Voice}
1415 context in the @qq{accepts} list.
1417 @cindex contexts, implicit
1418 @cindex implicit contexts
1419 @funindex \defaultchild
1421 Note that a context will be silently created implicitly if a
1422 command is encountered when there is no suitable context available
1425 Within a context definition, the type of subcontext to be
1426 implicitly created is specified using @code{\defaultchild}. A
1427 number of music events require a @samp{Bottom} context: when such
1428 an event is encountered, subcontexts are created recursively until
1429 reaching a context with no @samp{defaultchild} setting.
1431 Implicit context creation can at times give rise to unexpected new
1432 staves or scores. Using @code{\new} to create contexts explicitly
1433 avoids those problems.
1435 @cindex alignAboveContext
1436 @cindex alignBelowContext
1437 @funindex alignAboveContext
1438 @funindex alignBelowContext
1440 Sometimes a context is required to exist for just a brief period, a
1441 good example being the staff context for an ossia. This is usually
1442 achieved by introducing the context definition at the appropriate
1443 place in parallel with corresponding section of the main music.
1444 By default, the temporary context will be placed below all the
1445 existing contexts. To reposition it above the context called
1446 @qq{main}, it should be defined like this:
1449 @code{\new Staff \with @{ alignAboveContext = #"main" @} }
1452 A similar situation arises when positioning a temporary lyrics
1453 context within a multi-staved layout such as a @code{ChoirStaff},
1454 for example, when adding a second verse to a repeated section.
1455 By default the temporary lyrics context will be placed beneath the
1456 lower staves. By defining the temporary lyrics context with
1457 @code{alignBelowContext} it can be positioned correctly beneath
1458 the (named) lyrics context containing the first verse.
1460 Examples showing this repositioning of temporary contexts can be
1461 found elsewhere --- see @rlearning{Nesting music expressions},
1462 @ref{Modifying single staves} and @ref{Techniques specific to lyrics}.
1466 @rlearning{Nesting music expressions}.
1469 @ref{Modifying single staves},
1470 @ref{Techniques specific to lyrics}.
1473 @rprogram{An extra staff appears}.
1476 @file{ly/engraver-init.ly}.
1479 @node Explaining the Internals Reference
1480 @section Explaining the Internals Reference
1483 * Navigating the program reference::
1484 * Layout interfaces::
1485 * Determining the grob property::
1486 * Naming conventions::
1489 @node Navigating the program reference
1490 @subsection Navigating the program reference
1492 @c TODO remove this (it's in the LM)
1493 @c Replace with more factual directions
1495 Suppose we want to move the fingering indication in the fragment
1498 @lilypond[quote,fragment,verbatim]
1502 If you visit the documentation on fingering instructions (in
1503 @ref{Fingering instructions}), you will notice:
1508 Internals Reference: @rinternals{Fingering}.
1513 @c outdated info; probably will delete.
1515 This fragment points to two parts of the program reference: a page
1516 on @code{FingeringEvent} and one on @code{Fingering}.
1518 The page on @code{FingeringEvent} describes the properties of the music
1519 expression for the input @w{@code{-2}}. The page contains many links
1520 forward. For example, it says
1523 Accepted by: @rinternals{Fingering_engraver},
1527 That link brings us to the documentation for the Engraver, the
1531 This engraver creates the following layout objects: @rinternals{Fingering}.
1534 In other words, once the @code{FingeringEvent}s are interpreted, the
1535 @code{Fingering_engraver} plug-in will process them.
1539 @c I can't figure out what this is supposed to mean. -gp
1541 The @code{Fingering_engraver} is also listed to create
1542 @rinternals{Fingering} objects,
1544 @c old info? it doesn't make any sense to me with our current docs.
1546 second bit of information listed under @b{See also} in the Notation
1551 The programmer's reference is available as an HTML document. It is
1552 highly recommended that you read it in HTML form, either online or
1553 by downloading the HTML documentation. This section will be much more
1554 difficult to understand if you are using the
1558 Follow the link to @rinternals{Fingering}. At the top of the
1562 Fingering objects are created by: @rinternals{Fingering_engraver} and
1563 @rinternals{New_fingering_engraver}.
1566 By following related links inside the program reference, we can follow the
1567 flow of information within the program:
1571 @item @rinternals{Fingering}:
1572 @rinternals{Fingering} objects are created by:
1573 @rinternals{Fingering_engraver}
1575 @item @rinternals{Fingering_engraver}:
1576 Music types accepted: @rinternals{fingering-event}
1578 @item @rinternals{fingering-event}:
1579 Music event type @code{fingering-event} is in Music expressions named
1580 @rinternals{FingeringEvent}
1583 This path goes against the flow of information in the program: it
1584 starts from the output, and ends at the input event. You could
1585 also start at an input event, and read with the flow of
1586 information, eventually ending up at the output object(s).
1588 The program reference can also be browsed like a normal document. It
1589 contains chapters on
1591 @rinternals{Music definitions},
1594 @code{Music definitions}
1596 on @rinternals{Translation}, and the @rinternals{Backend}. Every
1597 chapter lists all the definitions used and all properties that may be
1601 @node Layout interfaces
1602 @subsection Layout interfaces
1604 @cindex interface, layout
1605 @cindex layout interface
1608 The HTML page that we found in the previous section describes the
1609 layout object called @rinternals{Fingering}. Such an object is a
1610 symbol within the score. It has properties that store numbers (like
1611 thicknesses and directions), but also pointers to related objects. A
1612 layout object is also called a @emph{Grob}, which is short for Graphical
1613 Object. For more details about Grobs, see @rinternals{grob-interface}.
1615 The page for @code{Fingering} lists the definitions for the
1616 @code{Fingering} object. For example, the page says
1619 @code{padding} (dimension, in staff space):
1625 which means that the number will be kept at a distance of at least 0.5
1629 Each layout object may have several functions as a notational or
1630 typographical element. For example, the Fingering object
1631 has the following aspects
1635 Its size is independent of the horizontal spacing, unlike slurs or beams.
1638 It is a piece of text. Granted, it is usually a very short text.
1641 That piece of text is typeset with a font, unlike slurs or beams.
1644 Horizontally, the center of the symbol should be aligned to the
1645 center of the note head.
1648 Vertically, the symbol is placed next to the note and the staff.
1651 The vertical position is also coordinated with other superscript
1652 and subscript symbols.
1655 Each of these aspects is captured in so-called @emph{interface}s,
1656 which are listed on the @rinternals{Fingering} page at the bottom
1659 This object supports the following interfaces:
1660 @rinternals{item-interface},
1661 @rinternals{self-alignment-interface},
1662 @rinternals{side-position-interface}, @rinternals{text-interface},
1663 @rinternals{text-script-interface}, @rinternals{font-interface},
1664 @rinternals{finger-interface}, and @rinternals{grob-interface}.
1667 Clicking any of the links will take you to the page of the respective
1668 object interface. Each interface has a number of properties. Some of
1669 them are not user-serviceable (@q{Internal properties}), but others
1672 We have been talking of @emph{the} @code{Fingering} object, but actually it
1673 does not amount to much. The initialization file (see
1674 @rlearning{Other sources of information})
1675 @file{scm/define-grobs.scm} shows the soul of the @q{object},
1680 (avoid-slur . around)
1681 (slur-padding . 0.2)
1682 (staff-padding . 0.5)
1683 (self-alignment-X . 0)
1684 (self-alignment-Y . 0)
1685 (script-priority . 100)
1686 (stencil . ,ly:text-interface::print)
1687 (direction . ,ly:script-interface::calc-direction)
1688 (font-encoding . fetaText)
1689 (font-size . -5) ; don't overlap when next to heads.
1690 (meta . ((class . Item)
1691 (interfaces . (finger-interface
1693 text-script-interface
1695 side-position-interface
1696 self-alignment-interface
1697 item-interface))))))
1701 As you can see, the @code{Fingering} object is nothing more than a
1702 bunch of variable settings, and the webpage in the Internals Reference
1703 is directly generated from this definition.
1706 @node Determining the grob property
1707 @subsection Determining the grob property
1709 @c TODO remove this (it's in the LM)
1710 @c Replace with more factual directions
1712 Recall that we wanted to change the position of the @b{2} in
1714 @lilypond[quote,fragment,verbatim]
1718 Since the @b{2} is vertically positioned next to its note, we have to
1719 meddle with the interface associated with this positioning. This is
1720 done using @code{side-position-interface}. The page for this interface
1724 @code{side-position-interface}
1726 Position a victim object (this one) next to other objects (the
1727 support). The property @code{direction} signifies where to put the
1728 victim object relative to the support (left or right, up or down?)
1733 Below this description, the variable @code{padding} is described as
1738 (dimension, in staff space)
1740 Add this much extra space between objects that are next to each other.
1744 By increasing the value of @code{padding}, we can move the
1745 fingering away from the note head. The following command inserts
1746 3 staff spaces of white
1747 between the note and the fingering:
1749 \once \override Voice.Fingering.padding = #3
1752 Inserting this command before the Fingering object is created,
1753 i.e., before @code{c2}, yields the following result:
1755 @lilypond[quote,fragment,verbatim]
1756 \once \override Voice.Fingering.padding = #3
1761 In this case, the context for this tweak is @code{Voice}. This
1762 fact can also be deduced from the program reference, for the page for
1763 the @rinternals{Fingering_engraver} plug-in says
1766 Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
1770 @node Naming conventions
1771 @subsection Naming conventions
1773 Another thing that is needed, is an overview of the various naming
1777 @item scheme functions: lowercase-with-hyphens (incl. one-word
1779 @item scheme functions: ly:plus-scheme-style
1780 @item music events, music classes and music properties:
1782 @item Grob interfaces: scheme-style
1783 @item backend properties: scheme-style (but X and Y!)
1784 @item contexts (and MusicExpressions and grobs): Capitalized or
1786 @item context properties: lowercaseFollowedByCamelCase
1788 Capitalized_followed_by_lowercase_and_with_underscores
1791 Questions to be answered:
1793 @item Which of these are conventions and which are rules?
1794 @item Which are rules of the underlying language, and which are
1798 @node Modifying properties
1799 @section Modifying properties
1801 @c TODO change the menu and subsection node names to use
1802 @c backslash once the new macro to handle the refs
1803 @c is available. Need to find and change all refs at
1804 @c the same time. -td
1807 * Overview of modifying properties::
1809 * The override command::
1810 * The tweak command::
1811 * set versus override::
1812 * Modifying alists::
1816 @node Overview of modifying properties
1817 @subsection Overview of modifying properties
1819 Each context is responsible for creating certain types of graphical
1820 objects. The settings used for printing these objects are also stored by
1821 context. By changing these settings, the appearance of objects can be
1824 There are two different kinds of properties stored in contexts:
1825 context properties and grob properties. Context properties are
1826 properties that apply to the context as a whole and control
1827 how the context itself is displayed. In contrast, grob properties
1828 apply to specific grob types that will be displayed in the context.
1830 The @code{\set} and @code{\unset} commands are used to change values
1831 for context properties. The @code{\override} and @code{\revert}
1832 commands are used to change values for grob properties.
1835 The syntax for this is
1838 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1841 Here @var{name} is the name of a graphical object, like
1842 @code{Stem} or @code{NoteHead}, and @var{property} is an internal
1843 variable of the formatting system (@q{grob property} or @q{layout
1844 property}). The latter is a symbol, so it must be quoted. The
1845 subsection @ref{Modifying properties}, explains what to fill in
1846 for @var{name}, @var{property}, and @var{value}. Here we only
1847 discuss the functionality of this command.
1852 \override Staff.Stem.thickness = #4.0
1856 makes stems thicker (the default is 1.3, with staff line thickness as a
1857 unit). Since the command specifies @code{Staff} as context, it only
1858 applies to the current staff. Other staves will keep their normal
1859 appearance. Here we see the command in action:
1861 @lilypond[quote,fragment,verbatim]
1863 \override Staff.Stem.thickness = #4.0
1869 The @code{\override} command changes the definition of the @code{Stem}
1870 within the current @code{Staff}. After the command is interpreted
1871 all stems are thickened.
1873 Analogous to @code{\set}, the @var{context} argument may be left out,
1874 causing the default context @code{Voice} to be used. Adding
1875 @code{\once} applies the change during one timestep only.
1877 @lilypond[quote,fragment,verbatim]
1879 \once \override Stem.thickness = #4.0
1884 The @code{\override} must be done before the object is
1885 started. Therefore, when altering @emph{Spanner} objects such as slurs
1886 or beams, the @code{\override} command must be executed at the moment
1887 when the object is created. In this example,
1889 @lilypond[quote,fragment,verbatim]
1890 \override Slur.thickness = #3.0
1892 \override Beam.beam-thickness = #0.6
1897 the slur is fatter but the beam is not. This is because the command for
1898 @code{Beam} comes after the Beam is started, so it has no effect.
1900 Analogous to @code{\unset}, the @code{\revert} command for a context
1901 undoes an @code{\override} command; like with @code{\unset}, it only
1902 affects settings that were made in the same context. In other words, the
1903 @code{\revert} in the next example does not do anything.
1906 \override Voice.Stem.thickness = #4.0
1907 \revert Staff.Stem.thickness
1910 Some tweakable options are called @q{subproperties} and reside inside
1911 properties. To tweak those, use commands of the form
1913 @c leave this as a long long
1915 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
1922 \override Stem.details.beamed-lengths = #'(4 4 3)
1928 Internals Reference:
1929 @rinternals{Backend},
1930 @rinternals{All layout objects},
1931 @rinternals{OverrideProperty},
1932 @rinternals{RevertProperty},
1933 @rinternals{PropertySet}.
1936 The back-end is not very strict in type-checking object properties.
1937 Cyclic references in Scheme values for properties can cause hangs
1938 or crashes, or both.
1941 @node The set command
1942 @subsection The @code{@bs{}set} command
1946 @cindex changing properties
1948 Each context has a set of @emph{properties}, variables contained
1949 in that context. Context properties are changed with the @code{\set}
1950 command, which has the following syntax:
1953 \set @var{context}.@var{property} = #@var{value}
1956 @var{value} is a Scheme object, which is why it must be preceded by
1957 the @code{#}@tie{}character.
1959 Contexts properties are usually named in
1960 @code{studlyCaps}. They mostly control the translation from
1961 music to notation, e.g. @code{localAlterations} (for determining
1962 whether to print accidentals), or @code{measurePosition} (for
1963 determining when to print a bar line). Context properties can
1964 change value over time while interpreting a piece of music;
1965 @code{measurePosition} is an obvious example of
1966 this. Context properties are modified with @code{\set}.
1968 For example, multimeasure rests will be combined into a single bar
1969 if the context property @code{skipBars} is set to @code{#t}:
1971 @lilypond[quote,fragment,verbatim]
1973 \set Score.skipBars = ##t
1977 If the @var{context} argument is left out, then the property will be
1978 set in the current bottom context (typically @code{ChordNames},
1979 @code{Voice}, @code{TabVoice}, or @code{Lyrics}).
1981 @lilypond[quote,fragment,verbatim]
1982 \set Score.autoBeaming = ##f
1985 \set autoBeaming = ##t
1993 The change is applied @q{on-the-fly}, during the music, so that the
1994 setting only affects the second group of eighth notes.
1996 Note that the bottom-most context does not always contain the property
1997 that you wish to change -- for example, attempting to set the
1998 @code{skipBars} property of the default bottom context, in this case
1999 @code{Voice}, will have no effect, because skipBars is a property of
2000 the @code{Score} context.
2002 @lilypond[quote,fragment,verbatim]
2008 Contexts are hierarchical, so if an enclosing context was specified, for
2009 example @code{Staff}, then the change would also apply to all
2010 @code{Voice}s in the current staff.
2014 The @code{\unset} command:
2017 \unset @var{context}.@var{property}
2021 is used to remove the definition of @var{property} from
2022 @var{context}. This command removes
2023 the definition only if it is set in @var{context}.
2024 Properties that have been set in enclosing contexts will
2025 not be altered by an unset in an enclosed context:
2027 @lilypond[quote,fragment,verbatim]
2028 \set Score.autoBeaming = ##t
2032 \unset Score.autoBeaming
2040 Like @code{\set}, the @var{context} argument does not have to be
2041 specified for a bottom context, so the two statements
2044 \set Voice.autoBeaming = ##t
2045 \set autoBeaming = ##t
2049 are equivalent if the current bottom context is @code{Voice}.
2053 Preceding a @code{\set} or @code{\unset} command by @code{\once}
2054 makes the setting apply to only a single time-step:
2056 @lilypond[quote,fragment,verbatim]
2058 \once \set fontSize = #4.7
2063 A full description of all available context properties is in the
2064 internals reference, see
2066 @rinternals{Tunable context properties}.
2069 Translation @expansion{} Tunable context properties.
2073 Internals Reference:
2074 @rinternals{Tunable context properties}.
2077 @node The override command
2078 @subsection The @code{\override} command
2080 @cindex grob properties
2081 @cindex properties, grob
2084 There is a special type of context property: the grob
2085 description. Grob descriptions are named in @code{StudlyCaps}
2086 (starting with capital letters). They contain the
2087 @q{default settings} for a particular kind of grob as an
2088 association list. See @file{scm/define-grobs.scm}
2089 to see the settings for each grob description. Grob descriptions
2090 are modified with @code{\override}.
2092 The syntax for the @code{\override} command is
2095 \override [@var{context}.]@var{GrobName}.@var{property} = #@var{value}
2098 For example, we can increase the thickness of a note stem by
2099 overriding the @code{thickness} property of the @code{Stem}
2102 @lilypond[quote,fragment,verbatim]
2104 \override Voice.Stem.thickness = #3.0
2108 If no context is specified in an @code{\override}, the bottom
2111 @lilypond[quote,fragment,verbatim]
2112 \override Staff.Stem.thickness = #3.0
2116 \override Stem.thickness = #0.5
2125 Some tweakable options are called @q{subproperties} and reside inside
2126 properties. To tweak those, use commands in the form
2129 \override Stem.details.beamed-lengths = #'(4 4 3)
2132 or to modify the ends of spanners, use a form like these
2135 \override TextSpanner.bound-details.left.text = #"left text"
2136 \override TextSpanner.bound-details.right.text = #"right text"
2140 @cindex reverting overrides
2141 @cindex overrides, reverting
2143 The effects of @code{\override} can be undone by @code{\revert}.
2145 The syntax for the @code{\revert} command is
2148 \revert [@var{context}.]@var{GrobName}.@var{property}
2153 @lilypond[quote,verbatim]
2156 \override Voice.Stem.thickness = #3.0
2158 \revert Voice.Stem.thickness
2163 The effects of @code{\override} and @code{\revert} apply to all
2164 grobs in the affected context from the current time forward:
2166 @lilypond[quote,verbatim]
2170 \override Staff.Stem.thickness = #3.0
2175 \revert Staff.Stem.thickness
2182 @cindex overriding for only one moment
2184 @code{\once} can be used with @code{\override} or @code{\revert}
2185 to affect only the current time step:
2187 @lilypond[quote,verbatim]
2190 \override Stem.thickness = #3.0
2195 \once \override Stem.thickness = #3.0
2203 Commands which change output generally look like
2206 \override Voice.Stem.thickness = #3.0
2210 To construct this tweak we must determine these bits of information:
2213 @item the context: here @code{Voice}.
2214 @item the layout object: here @code{Stem}.
2215 @item the layout property: here @code{thickness}.
2216 @item a sensible value: here @code{3.0}.
2219 @cindex internal documentation
2220 @cindex finding graphical objects
2221 @cindex graphical object descriptions
2224 @cindex internal documentation
2226 For many properties, regardless of the data type of the property, setting the
2227 property to false (@code{#f}) will result in turning it off, causing
2228 LilyPond to ignore that property entirely. This is particularly useful for
2229 turning off grob properties which may otherwise be causing problems.
2231 We demonstrate how to glean this information from the notation manual
2232 and the program reference.
2236 Internals Reference:
2237 @rinternals{Backend}
2240 @node The tweak command
2241 @subsection The @code{\tweak} command
2246 Changing grob properties
2247 with @code{\override} causes the changes to apply to all of the
2248 given grobs in the context at the moment the change applies.
2249 Sometimes, however, it is desirable to have changes apply to just
2250 one grob, rather than to all grobs in the affected context. This is
2251 accomplished with the @code{\tweak} command, which has the following
2255 \tweak [@var{layout-object}.]@var{grob-property} @var{value}
2258 Specifying @var{layout-object} is optional.
2259 The @code{\tweak} command applies to the music object that immediately
2260 follows @var{value} in the music stream.
2263 In some cases, it is possible to take a short-cut for tuning
2264 graphical objects. For objects that are created directly from
2265 an item in the input file, you can use the @code{\tweak} command.
2268 @lilypond[verbatim,quote]
2274 \tweak duration-log #1
2284 The main use of the @code{\tweak} command is to modify just
2285 one of a number of notation elements which start at the same musical
2286 moment, like the notes of a chord, or tuplet brackets which start
2289 The @code{\tweak} command sets a property in the following object
2290 directly, without requiring the grob name or context to be
2291 specified. For this to work, it is necessary for the @code{\tweak}
2292 command to remain immediately adjacent to the object to which it is
2293 to apply after the input file has been converted to a music stream.
2294 This is often not the case, as many additional elements are inserted
2295 into the music stream implicitly. For example, when a note which is
2296 not part of a chord is processed, LilyPond implicitly inserts a
2297 @code{ChordEvent} event before the note, so separating the tweak
2298 from the note. However, if chord symbols are placed round the
2299 tweak and the note, the @code{\tweak} command comes after the
2300 @code{ChordEvent} in the music stream, so remaining adjacent to the
2301 note, and able to modify it.
2305 @lilypond[verbatim,fragment,quote]
2306 <\tweak color #red c''>4
2312 @lilypond[verbatim,fragment,quote]
2313 \tweak color #red c''4
2318 For an introduction to the syntax and uses of the tweak command
2319 see @rlearning{Tweaking methods}.
2321 When several similar items are placed at the same musical moment,
2322 the @code{\override} command cannot be used to modify just one of
2323 them -- this is where the @code{\tweak} command must be used.
2324 Items which may appear more than once at the same musical moment
2325 include the following:
2327 @c TODO expand to include any further uses of \tweak
2329 @item note heads of notes inside a chord
2330 @item articulation signs on a single note
2331 @item ties between notes in a chord
2332 @item tuplet brackets starting at the same time
2335 @c TODO add examples of these
2337 @cindex chord, modifying one note in
2339 In this example, the color of one note head and the type of another
2340 note head are modified within a single chord:
2342 @lilypond[verbatim,fragment,quote]
2347 \tweak duration-log #1
2352 @code{\tweak} can be used to modify slurs:
2354 @lilypond[verbatim,quote]
2355 \relative { c'-\tweak thickness #5 ( d e f) }
2359 For the @code{\tweak} command to work, it must
2360 remain immediately adjacent to the object to which it is
2361 to apply after the input file has been converted to a music stream.
2362 Tweaking a whole chord does not do anything since its music event
2363 only acts as a container, and all layout objects are created from events
2364 inside of the @code{EventChord}:
2366 @lilypond[verbatim,fragment,quote]
2367 \tweak color #red c''4
2368 \tweak color #red <c'' e''>4
2369 <\tweak color #red c'' e''>4
2372 The simple @code{\tweak} command cannot be used to modify any object
2373 that is not directly created from the input. In particular
2374 it will not affect stems, automatic
2375 beams or accidentals, since these are generated later by
2376 @code{NoteHead} layout objects rather than by music elements in the
2379 Such indirectly created layout objects can be tweaked using the form
2380 of the @code{\tweak} command in which the grob name is specified
2383 @lilypond[fragment,verbatim,quote]
2384 \tweak Stem.color #red
2385 \tweak Beam.color #green c''8 e''
2386 <c'' e'' \tweak Accidental.font-size #-3 ges''>4
2389 @code{\tweak} cannot be used to modify clefs or time
2390 signatures, since these become separated from any preceding
2391 @code{\tweak} command in the input stream by the automatic
2392 insertion of extra elements required to specify the context.
2394 Several @code{\tweak} commands may be placed before a
2395 notational element -- all affect it:
2397 @lilypond[verbatim,fragment,quote]
2399 -\tweak style #'dashed-line
2400 -\tweak dash-fraction #0.2
2401 -\tweak thickness #3
2407 The music stream which is generated from a section of an input file,
2408 including any automatically inserted elements, may be examined,
2409 see @rextend{Displaying music expressions}. This may be helpful in
2410 determining what may be modified by a @code{\tweak} command, or
2411 in determining how to adjust the input to make a @code{\tweak}
2416 @rlearning{Tweaking methods}.
2419 @rextend{Displaying music expressions}.
2423 @cindex tweaking control points
2424 @cindex control points, tweaking
2426 The @code{\tweak} command cannot be used to modify the control
2427 points of just one of several ties in a chord, other than the first
2428 one encountered in the input file.
2430 @node set versus override
2431 @subsection @code{\set} vs. @code{\override}
2433 @c TODO Should't a bunch of that be explained earlier?
2437 Both @code{\set} and @code{\override} manipulate properties
2438 associated with contexts. In either case, properties heed the
2439 hierarchy of contexts: properties not set in a context itself show
2440 the values of the respective parent context.
2442 Values and lifetime of context properties are dynamic and only
2443 available when music is being interpreted, @q{iterated}. At the
2444 time of context creation, properties are initialized from the
2445 corresponding context definition and possible context
2446 modifications. Afterwards, changes are achieved with
2447 property-setting commands in the music itself.
2449 Now grob definitions are a special category of context properties.
2450 Since their structure, bookkeeping and use is different from
2451 ordinary context properties, they are accessed with a different
2452 set of commands, and treated separately in the documentation.
2454 As opposed to plain context properties, grob definitions are
2455 subdivided into grob properties. A @qq{grob} (graphical object)
2456 is usually created by an engraver at the time of interpreting a
2457 music expression and receives its initial properties from the
2458 current grob definition of the engraver's context. The engraver
2459 (or other @q{backend} parts of LilyPond) may subsequently add or
2460 change properties to the grob, but that does not affect the
2461 context's grob definition.
2463 What we call @q{grob properties} in the context of user-level
2464 tweaking are actually the properties of a context's grob
2465 definition. In contrast to ordinary context properties, grob
2466 definitions have the bookkeeping required to keep track of its
2467 parts, the individual grob properties (and even subproperties of
2468 them) separately so that it is possible to define those parts in
2469 different contexts and have the overall grob definition at the
2470 time of grob creation be assembled from pieces provided in
2471 different contexts among the current context and its parents.
2473 Grob definitions are manipulated using @code{\override} and
2474 @code{\revert} and have a name starting with a capital letter
2475 (like @samp{NoteHead}) whereas ordinary context properties are
2476 manipulated using @code{\set} and @code{\unset} and are named
2477 starting with a lowercase letter.
2479 @cindex tweak, relation to @code{\override}
2481 @funindex \overrideProperty
2482 The special commands @code{\tweak} and @code{\overrideProperty}
2483 change grob properties bypassing context properties completely.
2484 Instead they catch grobs as they are being created and then
2485 directly set properties on them when they originate from a tweaked
2486 music event or are of a particular kind, respectively.
2488 @node Modifying alists
2489 @subsection Modifying alists
2491 Some user-configurable properties are internally represented as
2492 @emph{alists} (association lists), which store pairs of
2493 @emph{keys} and @emph{values}. The structure of an alist is:
2496 '((@var{key1} . @var{value1})
2497 (@var{key2} . @var{value2})
2498 (@var{key3} . @var{value3})
2502 If an alist is a grob property or @code{\paper} variable, its keys
2503 can be modified individually without affecting other keys.
2505 For example, to reduce the space between adjacent staves in a
2506 staff-group, use the @code{staff-staff-spacing} property of the
2507 @code{StaffGrouper} grob. The property is an alist with four
2508 keys: @code{basic-distance}, @code{minimum-distance},
2509 @code{padding}, and @code{stretchability}. The standard settings
2510 for this property are listed in the @qq{Backend} section of the
2511 Internals Reference (see @rinternals{StaffGrouper}):
2514 '((basic-distance . 9)
2515 (minimum-distance . 7)
2517 (stretchability . 5))
2520 One way to bring the staves closer together is by reducing the
2521 value of the @code{basic-distance} key (@code{9}) to match the
2522 value of @code{minimum-distance} (@code{7}). To modify a single
2523 key individually, use a @emph{nested declaration}:
2525 @lilypond[quote,verbatim]
2526 % default space between staves
2528 \new Staff { \clef treble c''1 }
2529 \new Staff { \clef bass c1 }
2532 % reduced space between staves
2533 \new PianoStaff \with {
2534 % this is the nested declaration
2535 \override StaffGrouper.staff-staff-spacing.basic-distance = #7
2537 \new Staff { \clef treble c''1 }
2538 \new Staff { \clef bass c1 }
2542 Using a nested declaration will update the specified key (such as
2543 @code{basic-distance} in the above example) without altering any
2544 other keys already set for the same property.
2546 Now suppose we want the staves to be as close as possible without
2547 overlapping. The simplest way to do this is to set all four alist
2548 keys to zero. However, it is not necessary to enter four nested
2549 declarations, one for each key. Instead, the property can be
2550 completely re-defined with one declaration, as an alist:
2552 @lilypond[quote,verbatim]
2553 \new PianoStaff \with {
2554 \override StaffGrouper.staff-staff-spacing =
2555 #'((basic-distance . 0)
2556 (minimum-distance . 0)
2558 (stretchability . 0))
2560 \new Staff { \clef treble c''1 }
2561 \new Staff { \clef bass c1 }
2565 Note that any keys not explicitly listed in the alist definition
2566 will be reset to their @emph{default-when-unset} values. In the
2567 case of @code{staff-staff-spacing}, any unset key-values would be
2568 reset to zero (except @code{stretchability}, which takes the value
2569 of @code{basic-distance} when unset). Thus the following two
2570 declarations are equivalent:
2573 \override StaffGrouper.staff-staff-spacing =
2574 #'((basic-distance . 7))
2576 \override StaffGrouper.staff-staff-spacing =
2577 #'((basic-distance . 7)
2578 (minimum-distance . 0)
2580 (stretchability . 7))
2583 One (possibly unintended) consequence of this is the removal of
2584 any standard settings that are set in an initialization file and
2585 loaded each time an input file is compiled. In the above example,
2586 the standard settings for @code{padding} and
2587 @code{minimum-distance} (defined in @file{scm/define-grobs.scm})
2588 are reset to their default-when-unset values (zero for both keys).
2589 Defining a property or variable as an alist (of any size) will
2590 always reset all unset key-values to their default-when-unset
2591 values. Unless this is the intended result, it is safer to update
2592 key-values individually with a nested declaration.
2594 @warning{Nested declarations will not work for context property
2595 alists (such as @code{beamExceptions}, @code{keyAlterations},
2596 @code{timeSignatureSettings}, etc.). These properties can only be
2597 modified by completely re-defining them as alists.}
2600 @node Useful concepts and properties
2601 @section Useful concepts and properties
2606 * Direction and placement::
2607 * Distances and measurements::
2609 * Staff symbol properties::
2611 * Visibility of objects::
2613 * Rotating objects::
2617 @subsection Input modes
2619 The way in which the notation contained within an input file is
2620 interpreted is determined by the current input mode.
2622 @subsubsubheading Chord mode
2624 This is activated with the @code{\chordmode} command, and causes
2625 input to be interpreted with the syntax of chord notation, see
2626 @ref{Chord notation}. Chords are rendered as notes on a staff.
2628 Chord mode is also activated with the @code{\chords} command.
2629 This also creates a new @code{ChordNames} context and
2630 causes the following input to be interpreted with the syntax of
2631 chord notation and rendered as chord names in the @code{ChordNames}
2632 context, see @ref{Printing chord names}.
2634 @subsubsubheading Drum mode
2636 This is activated with the @code{\drummode} command, and causes
2637 input to be interpreted with the syntax of drum notation, see
2638 @ref{Basic percussion notation}.
2640 Drum mode is also activated with the @code{\drums} command.
2641 This also creates a new @code{DrumStaff} context and causes the
2642 following input to be interpreted with the syntax of drum notation
2643 and rendered as drum symbols on a drum staff, see
2644 @ref{Basic percussion notation}.
2646 @subsubsubheading Figure mode
2648 This is activated with the @code{\figuremode} command, and causes
2649 input to be interpreted with the syntax of figured bass, see
2650 @ref{Entering figured bass}.
2652 Figure mode is also activated with the @code{\figures} command.
2653 This also creates a new @code{FiguredBass} context and causes the
2654 following input to be interpreted with the figured bass syntax
2655 and rendered as figured bass symbols in the @code{FiguredBass}
2656 context, see @ref{Introduction to figured bass}.
2658 @subsubsubheading Fret and tab modes
2660 There are no special input modes for entering fret and tab symbols.
2662 To create tab diagrams, enter notes or chords in note mode and
2663 render them in a @code{TabStaff} context, see
2664 @ref{Default tablatures}.
2666 To create fret diagrams above a staff, you have two choices.
2667 You can either use the @code{FretBoards} context (see
2668 @ref{Automatic fret diagrams} or you can enter them as a markup
2669 above the notes using the @code{\fret-diagram} command (see
2670 @ref{Fret diagram markups}).
2672 @subsubsubheading Lyrics mode
2674 This is activated with the @code{\lyricmode} command, and causes
2675 input to be interpreted as lyric syllables with optional durations
2676 and associated lyric modifiers, see @ref{Vocal music}.
2678 Lyric mode is also activated with the @code{\addlyrics} command.
2679 This also creates a new @code{Lyrics} context and an implicit
2680 @code{\lyricsto} command which associates the following lyrics
2681 with the preceding music.
2683 @subsubsubheading Markup mode
2685 This is activated with the @code{\markup} command, and causes
2686 input to be interpreted with the syntax of markup, see
2687 @ref{Text markup commands}.
2689 @subsubsubheading Note mode
2691 This is the default mode or it may be activated with the
2692 @code{\notemode} command. Input is interpreted as pitches,
2693 durations, markup, etc and typeset as musical notation on a staff.
2695 It is not normally necessary to specify note mode explicitly, but
2696 it may be useful to do so in certain situations, for example if you
2697 are in lyric mode, chord mode or any other mode and want to insert
2698 something that only can be done with note mode syntax.
2701 @node Direction and placement
2702 @subsection Direction and placement
2704 In typesetting music the direction and placement of many items is
2705 a matter of choice. For example, the stems of notes can
2706 be directed up or down; lyrics, dynamics, and other expressive
2707 marks may be placed above or below the staff; text may be aligned
2708 left, right or center; etc. Most of these choices may be left to
2709 be determined automatically by LilyPond, but in some cases it may
2710 be desirable to force a particular direction or placement.
2713 * Articulation direction indicators::
2714 * The direction property::
2717 @node Articulation direction indicators
2718 @unnumberedsubsubsec Articulation direction indicators
2720 By default some directions are always up or always down (e.g.
2721 dynamics or fermata), while other things can alternate between
2722 up or down based on the stem direction (like slurs or accents).
2724 @c TODO Add table showing these
2726 The default action may be overridden by prefixing the articulation
2727 by a @emph{direction indicator}. Three direction indicators are
2728 available: @code{^} (meaning @qq{up}), @code{_} (meaning @qq{down})
2729 and @code{-} (meaning @qq{use default direction}). The direction
2730 indicator can usually be omitted, in which case @code{-} is assumed,
2731 but a direction indicator is @strong{always} required before
2734 @item @code{\tweak} commands
2735 @item @code{\markup} commands
2736 @item @code{\tag} commands
2737 @item string markups, e.g. -"string"
2738 @item fingering instructions, e.g. @w{@code{-1}}
2739 @item articulation shortcuts, e.g. @w{@code{-.}}, @w{@code{->}}, @w{@code{--}}
2742 Direction indicators affect only the next note:
2744 @lilypond[verbatim,quote]
2753 @node The direction property
2754 @unnumberedsubsubsec The direction property
2756 The position or direction of many layout objects is controlled by the
2757 @code{direction} property.
2759 The value of the @code{direction} property may be set to @code{1},
2760 meaning @qq{up} or @qq{above}, or to @w{@code{-1}}, meaning @qq{down} or
2761 @qq{below}. The symbols @code{UP} and @code{DOWN} may be used instead
2762 of @code{1} and @w{@code{-1}} respectively. The default direction may
2763 be specified by setting @code{direction} to @code{0} or @code{CENTER}.
2764 Alternatively, in many cases predefined commands exist to specify the
2765 direction. These are of the form
2768 @code{\xxxUp}, @code{\xxxDown} or @code{\xxxNeutral}
2772 where @code{\xxxNeutral} means @qq{use the default} direction.
2773 See @rlearning{Within-staff objects}.
2775 In a few cases, arpeggio for example, the value of the @code{direction}
2776 property can specify whether the object is to be placed to the right or
2777 left of the parent. In this case @w{@code{-1}} or @code{LEFT} means
2778 @qq{to the left} and @code{1} or @code{RIGHT} means @qq{to the right}.
2779 @code{0} or @code{CENTER} means @qq{use the default} direction.
2782 These all have side-axis set to #X
2783 AmbitusAccidental - direction has no effect
2785 StanzaNumber - not tried
2786 TrillPitchAccidental - not tried
2787 TrillPitchGroup - not tried
2790 These indications affect all notes until they are canceled.
2792 @lilypond[verbatim,quote]
2803 In polyphonic music, it is generally better to specify an explicit
2804 @code{voice} than change an object's direction. For more information.
2805 See @ref{Multiple voices}.
2809 @rlearning{Within-staff objects}.
2812 @ref{Multiple voices}.
2815 @node Distances and measurements
2816 @subsection Distances and measurements
2818 @cindex distances, absolute
2819 @cindex distances, scaled
2826 Distances in LilyPond are of two types: absolute and scaled.
2828 Absolute distances are used for specifying margins, indents, and
2829 other page layout details, and are by default specified in
2830 millimeters. Distances may be specified in other units by
2831 following the quantity by @code{\mm}, @code{\cm},
2832 @code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27 of
2833 an inch). Page layout distances can also be specified in scalable
2834 units (see the following paragraph) by appending
2835 @code{\staff-space} to the quantity. Page layout is described in
2836 detail in @ref{Page layout}.
2838 Scaled distances are always specified in units of the staff-space
2839 or, rarely, the half staff-space. The staff-space is the distance
2840 between two adjacent staff lines. The default value can be changed
2841 globally by setting the global staff size, or it can be overridden
2842 locally by changing the @code{staff-space} property of
2843 @code{StaffSymbol}. Scaled distances automatically scale with any
2844 change to the either the global staff size or the
2845 @code{staff-space} property of @code{StaffSymbol}, but fonts scale
2846 automatically only with changes to the global staff size.
2847 The global staff size thus enables the overall size of a rendered
2848 score to be easily varied. For the methods of setting the global
2849 staff size see @ref{Setting the staff size}.
2853 If just a section of a score needs to be rendered to a different
2854 scale, for example an ossia section or a footnote, the global staff
2855 size cannot simply be changed as this would affect the entire score.
2856 In such cases the change in size is made by overriding both the
2857 @code{staff-space} property of @code{StaffSymbol} and the size of
2858 the fonts. A Scheme function, @code{magstep}, is available to
2859 convert from a font size change to the equivalent change in
2860 @code{staff-space}. For an explanation and an example of its use,
2861 see @rlearning{Length and thickness of objects}.
2865 @rlearning{Length and thickness of objects}.
2869 @ref{Setting the staff size}.
2873 @subsection Dimensions
2876 @cindex bounding box
2878 The dimensions of a graphical object specify the positions of the left
2879 and right edges and the bottom and top edges of the objects' bounding
2880 box as distances from the objects' reference point in units of
2881 staff-spaces. These positions are usually coded as two Scheme pairs.
2882 For example, the text markup command @code{\with-dimensions} takes
2883 three arguments, the first two of which are a Scheme pair giving the
2884 left and right edge positions and a Scheme pair giving the bottom and
2888 \with-dimensions #'(-5 . 10) #'(-3 . 15) @var{arg}
2891 This specifies a bounding box for @var{arg} with its left edge at -5,
2892 its right edge at 10, its bottom edge at -3 and its top edge at 15,
2893 all measured from the objects' reference point in units of
2898 @ref{Distances and measurements}.
2901 @node Staff symbol properties
2902 @subsection Staff symbol properties
2904 @cindex adjusting staff symbol
2905 @cindex drawing staff symbol
2906 @cindex staff symbol, setting of
2908 @c TODO Extend or remove this section. See also NR 1.6.2 Staff symbol
2909 @c Need to think of uses for these properties. Eg 'line-positions
2910 @c is used in a snippet to thicken centre line.
2911 @c If retained, add @ref to here in 1.6.2 -td
2913 The vertical position of staff lines and the number of staff lines
2914 can be defined at the same time. As the following example shows,
2915 note positions are not influenced by the staff line positions.
2917 @warning{The @code{'line-positions} property overrides the
2918 @code{'line-count} property. The number of staff lines is
2919 implicitly defined by the number of elements in the list of values
2920 for @code{'line-positions}.}
2922 @lilypond[verbatim,quote]
2924 \override StaffSymbol.line-positions = #'(7 3 0 -4 -6 -7)
2926 \relative { a4 e' f b | d1 }
2929 The width of a staff can be modified. The units are staff
2930 spaces. The spacing of objects inside the staff is not affected by
2933 @lilypond[verbatim,quote]
2935 \override StaffSymbol.width = #23
2937 \relative { a4 e' f b | d1 }
2942 @subsection Spanners
2944 Many objects of musical notation extend over several notes or even
2945 several bars. Examples are slurs, beams, tuplet brackets, volta
2946 repeat brackets, crescendi, trills, and glissandi. Such objects
2947 are collectively called @qq{spanners}, and have special properties to control
2948 their appearance and behaviour. Some of these properties are common
2949 to all spanners; others are restricted to a sub-set of the spanners.
2951 All spanners support the @code{spanner-interface}. A few, essentially
2952 those that draw a straight line between the two objects, support in
2953 addition the @code{line-spanner-interface}.
2956 * Using the spanner-interface::
2957 * Using the line-spanner-interface::
2960 @node Using the spanner-interface
2961 @unnumberedsubsubsec Using the @code{spanner-interface}
2963 This interface provides two properties that apply to several spanners.
2965 @subsubsubheading The @code{minimum-length} property
2967 The minimum length of the spanner is specified by the
2968 @code{minimum-length} property. Increasing this usually has the
2969 necessary effect of increasing the spacing of the notes between the
2970 two end points. However, this override has no effect on
2971 many spanners, as their length is determined by other considerations.
2972 A few examples where it is effective are shown below.
2982 Works as long as callback is made:
2986 Works not at all for:
2995 @lilypond[verbatim,quote,fragment]
2998 % increase the length of the tie
2999 -\tweak minimum-length #5
3003 @lilypond[verbatim,quote]
3004 \relative \compressMMRests {
3007 % increase the length of the rest bar
3008 \once \override MultiMeasureRest.minimum-length = #20
3014 @lilypond[verbatim,quote]
3017 % increase the length of the hairpin
3018 \override Hairpin.minimum-length = #20
3023 This override can also be used to increase the length of slurs and
3026 @lilypond[verbatim,quote]
3030 -\tweak minimum-length #5
3035 -\tweak minimum-length #5
3040 For some layout objects, the @code{minimum-length} property becomes
3041 effective only if the @code{set-spacing-rods} procedure is called
3042 explicitly. To do this, the @code{springs-and-rods} property should
3043 be set to @code{ly:spanner::set-spacing-rods}. For example,
3044 the minimum length of a glissando has no effect unless the
3045 @code{springs-and-rods} property is set:
3047 @lilypond[verbatim,fragment,quote]
3051 % not effective alone
3052 \once \override Glissando.minimum-length = #20
3055 % effective only when both overrides are present
3056 \once \override Glissando.minimum-length = #20
3057 \once \override Glissando.springs-and-rods = #ly:spanner::set-spacing-rods
3061 The same is true of the @code{Beam} object:
3063 @lilypond[verbatim,fragment,quote]
3064 % not effective alone
3065 \once \override Beam.minimum-length = #20
3068 % effective only when both overrides are present
3069 \once \override Beam.minimum-length = #20
3070 \once \override Beam.springs-and-rods = #ly:spanner::set-spacing-rods
3074 @subsubsubheading The @code{to-barline} property
3076 The second useful property of the @code{spanner-interface} is
3077 @code{to-barline}. By default this is true, causing hairpins and
3078 other spanners which are terminated on the first note of a measure to
3079 end instead on the immediately preceding bar line. If set to false,
3080 the spanner will extend beyond the bar line and end on the note
3083 @lilypond[verbatim,quote]
3085 a' \< a a a a \! a a a \break
3086 \override Hairpin.to-barline = ##f
3087 a \< a a a a \! a a a
3091 This property is not effective for all spanners. For example,
3092 setting it to @code{#t} has no effect on slurs or phrasing slurs
3093 or on other spanners for which terminating on the bar line would
3096 @node Using the line-spanner-interface
3097 @unnumberedsubsubsec Using the @code{line-spanner-interface}
3099 Objects which support the @code{line-spanner-interface} include
3102 @item @code{DynamicTextSpanner}
3103 @item @code{Glissando}
3104 @item @code{TextSpanner}
3105 @item @code{TrillSpanner}
3106 @item @code{VoiceFollower}
3109 The routine responsible for drawing the stencils for these spanners is
3110 @code{ly:line-spanner::print}. This routine determines the
3111 exact location of the two end points and draws a line
3112 between them, in the style requested. The locations of the two
3113 end points of the spanner are computed on-the-fly, but it is
3114 possible to override their Y-coordinates. The
3115 properties which need to be specified are nested
3116 two levels down within the property hierarchy, but the syntax of
3117 the @code{\override} command is quite simple:
3119 @lilypond[quote,fragment,verbatim]
3121 \once \override Glissando.bound-details.left.Y = #3
3122 \once \override Glissando.bound-details.right.Y = #-2
3126 The units for the @code{Y} property are @code{staff-space}s,
3127 with the center line of the staff being the zero point.
3128 For the glissando, this is the value for @code{Y} at the
3129 X-coordinate corresponding to the center point of each note head,
3130 if the line is imagined to be extended to there.
3132 If @code{Y} is not set, the value is computed from the vertical
3133 position of the corresponding attachment point of the spanner.
3135 In case of a line break, the values for the end points are
3136 specified by the @code{left-broken} and @code{right-broken}
3137 sub-lists of @code{bound-details}. For example:
3139 @lilypond[ragged-right,fragment,verbatim,quote]
3140 \override Glissando.breakable = ##t
3141 \override Glissando.bound-details.right-broken.Y = #-3
3142 c''1 \glissando \break
3147 A number of further properties of the @code{left} and
3148 @code{right} sub-lists of the @code{bound-details} property
3149 may be modified in the same way as @code{Y}:
3153 This sets the Y-coordinate of the end point, in @code{staff-space}s
3154 offset from the staff center line. By default, it is the center of
3155 the bound object, so a glissando points to the vertical center of
3158 For horizontal spanners, such as text spanners and trill spanners,
3159 it is hardcoded to 0.
3162 This determines where the line starts and ends in the X-direction,
3163 relative to the bound object. So, a value of @w{@code{-1}} (or
3164 @code{LEFT}) makes the line start/end at the left side of the note
3165 head it is attached to.
3168 This is the absolute X-coordinate of the end point. It is usually
3169 computed on the fly, and overriding it has little useful effect.
3172 Line spanners may have symbols at the beginning or end, which is
3173 contained in this sub-property. This is for internal use; it is
3174 recommended that @code{text} be used instead.
3177 This is a markup that is evaluated to yield the stencil. It is used
3178 to put @i{cresc.}, @i{tr} and other text on horizontal spanners.
3180 @lilypond[quote,ragged-right,fragment,verbatim]
3181 \override TextSpanner.bound-details.left.text
3182 = \markup { \small \bold Slower }
3183 \relative { c''2\startTextSpan b c a\stopTextSpan }
3186 @item stencil-align-dir-y
3187 @item stencil-offset
3188 Without setting one of these, the stencil is simply put at the
3189 end-point, centered on the line, as defined by the @code{X} and
3190 @code{Y} sub-properties. Setting either @code{stencil-align-dir-y}
3191 or @code{stencil-offset} will move the symbol at the edge vertically
3192 relative to the end point of the line:
3194 @lilypond[quote,fragment,verbatim]
3195 \override TextSpanner.bound-details.left.stencil-align-dir-y = #-2
3196 \override TextSpanner.bound-details.right.stencil-align-dir-y = #UP
3198 \override TextSpanner.bound-details.left.text = #"ggg"
3199 \override TextSpanner.bound-details.right.text = #"hhh"
3201 \relative { c'4^\startTextSpan c c c \stopTextSpan }
3204 Note that negative values move the text @emph{up}, contrary to the
3205 effect that might be expected, as a value of @w{@code{-1}} or
3206 @code{DOWN} means align the @emph{bottom} edge of the text with
3207 the spanner line. A value of @code{1} or @code{UP} aligns
3208 the top edge of the text with the spanner line.
3211 Setting this sub-property to @code{#t} produces an arrowhead at the
3215 This sub-property controls the space between the specified
3216 end point of the line and the actual end. Without padding, a
3217 glissando would start and end in the center of each note head.
3221 The music function @code{\endSpanners} terminates the spanner
3222 which starts on the immediately following note prematurely. It
3223 is terminated after exactly one note, or at the following bar line
3224 if @code{to-barline} is true and a bar line occurs before the next
3227 @lilypond[verbatim,quote,ragged-right]
3230 c2 \startTextSpan c2 c2
3236 When using @code{\endSpanners} it is not necessary to close
3237 \startTextSpan with \stopTextSpan, nor is it necessary to close
3238 hairpins with @code{\!}.
3241 Internals Reference:
3242 @rinternals{TextSpanner},
3243 @rinternals{Glissando},
3244 @rinternals{VoiceFollower},
3245 @rinternals{TrillSpanner},
3246 @rinternals{line-spanner-interface}.
3249 @node Visibility of objects
3250 @subsection Visibility of objects
3252 @cindex objects, visibility of
3253 @cindex grobs, visibility of
3254 @cindex visibility of objects
3256 There are four main ways in which the visibility of layout objects
3257 can be controlled: their stencil can be removed, they can be made
3258 transparent, they can be colored white, or their
3259 @code{break-visibility} property can be overridden. The first
3260 three apply to all layout objects; the last to just a few -- the
3261 @emph{breakable} objects. The Learning Manual introduces these
3262 four techniques, see @rlearning{Visibility and color of objects}.
3264 There are also a few other techniques which are specific to
3265 certain layout objects. These are covered under Special
3269 * Removing the stencil::
3270 * Making objects transparent::
3271 * Painting objects white::
3272 * Using break-visibility::
3273 * Special considerations::
3277 @node Removing the stencil
3278 @unnumberedsubsubsec Removing the stencil
3280 @cindex stencil, removing
3283 Every layout object has a stencil property. By default this is set
3284 to the specific function which draws that object. If this property
3285 is overridden to @code{#f} no function will be called and the object
3286 will not be drawn. The default action can be recovered with
3289 @lilypond[quote,fragment,verbatim]
3291 \override Score.BarLine.stencil = ##f
3293 \revert Score.BarLine.stencil
3297 This rather common operation has a shortcut @code{\omit}:
3299 @lilypond[quote,fragment,verbatim]
3303 \undo \omit Score.BarLine
3307 @node Making objects transparent
3308 @unnumberedsubsubsec Making objects transparent
3310 @cindex transparent, making objects
3313 Every layout object has a transparent property which by default is
3314 set to @code{#f}. If set to @code{#t} the object still occupies
3315 space but is made invisible.
3317 @lilypond[quote,fragment,verbatim]
3319 \once \override NoteHead.transparent = ##t
3323 This rather common operation has a shortcut @code{\hide}:
3325 @lilypond[quote,fragment,verbatim]
3327 \once \hide NoteHead
3331 @node Painting objects white
3332 @unnumberedsubsubsec Painting objects white
3334 @cindex objects, coloring
3335 @cindex coloring objects
3337 @cindex printing order
3338 @cindex overwriting objects
3339 @cindex objects, overwriting
3340 @cindex grobs, overwriting
3342 Every layout object has a color property which by default is set
3343 to @code{black}. If this is overridden to @code{white} the object
3344 will be indistinguishable from the white background. However,
3345 if the object crosses other objects the color of the crossing
3346 points will be determined by the order in which they are drawn,
3347 and this may leave a ghostly image of the white object, as shown
3350 @lilypond[quote,fragment,verbatim]
3351 \override Staff.Clef.color = #white
3355 This may be avoided by changing the order of printing the objects.
3356 All layout objects have a @code{layer} property which should be set
3357 to an integer. Objects with the lowest value of @code{layer} are
3358 drawn first, then objects with progressively higher values are drawn,
3359 so objects with higher values overwrite objects with lower values.
3360 By default most objects are assigned a @code{layer} value of
3361 @code{1}, although a few objects, including @code{StaffSymbol} and
3362 @code{BarLine}, are assigned a value of @code{0}. The order of
3363 printing objects with the same value of @code{layer} is indeterminate.
3365 In the example above the white clef, with a default @code{layer}
3366 value of @code{1}, is drawn after the staff lines (default
3367 @code{layer} value @code{0}), so overwriting them. To change this,
3368 the @code{Clef} object must be given in a lower value of
3369 @code{layer}, say @w{@code{-1}}, so that it is drawn earlier:
3371 @lilypond[quote,fragment,verbatim]
3372 \override Staff.Clef.color = #white
3373 \override Staff.Clef.layer = #-1
3377 @node Using break-visibility
3378 @unnumberedsubsubsec Using break-visibility
3380 @c TODO Add making other objects breakable
3382 @cindex break-visibility
3384 Most layout objects are printed only once, but some like
3385 bar lines, clefs, time signatures and key signatures, may need
3386 to be printed twice when a line break occurs -- once at the end
3387 of the line and again at the start of the next line. Such
3388 objects are called @emph{breakable}, and have a property, the
3389 @code{break-visibility} property to control their visibility
3390 at the three positions in which they may appear -- at the
3391 start of a line, within a line if they are changed, and at the
3392 end of a line if a change takes place there.
3394 For example, the time signature
3395 by default will be printed at the start of the first line, but
3396 nowhere else unless it changes, when it will be printed at the
3397 point at which the change occurs. If this change occurs at the
3398 end of a line the new time signature will be printed at the start
3399 of the next line and a cautionary time signature will be printed
3400 at the end of the previous line as well.
3402 This behaviour is controlled by the @code{break-visibility}
3403 property, which is explained in
3404 @c Leave this ref on a newline - formats incorrectly otherwise -td
3405 @rlearning{Visibility and color of objects}. This property takes
3406 a vector of three booleans which, in order, determine whether the
3407 object is printed at the end of, within the body of, or at the
3408 beginning of a line. Or to be more precise, before a line break,
3409 where there is no line break, or after a line break.
3411 Alternatively, these eight combinations may be specified
3412 by pre-defined functions, defined in @file{scm/output-lib.scm},
3413 where the last three columns indicate whether the layout objects
3414 will be visible in the positions shown at the head of the columns:
3416 @multitable {@code{begin-of-line-invisible}} {@code{#(#t #t #t)}} {Before} {At no} {After}
3417 @headitem Function @tab Vector @tab Before @tab At no @tab After
3418 @headitem form @tab form @tab break @tab break @tab break
3420 @item @code{all-visible} @tab @code{#(#t #t #t)} @tab yes @tab yes @tab yes
3421 @item @code{begin-of-line-visible} @tab @code{#(#f #f #t)} @tab no @tab no @tab yes
3422 @item @code{center-visible} @tab @code{#(#f #t #f)} @tab no @tab yes @tab no
3423 @item @code{end-of-line-visible} @tab @code{#(#t #f #f)} @tab yes @tab no @tab no
3424 @item @code{begin-of-line-invisible} @tab @code{#(#t #t #f)} @tab yes @tab yes @tab no
3425 @item @code{center-invisible} @tab @code{#(#t #f #t)} @tab yes @tab no @tab yes
3426 @item @code{end-of-line-invisible} @tab @code{#(#f #t #t)} @tab no @tab yes @tab yes
3427 @item @code{all-invisible} @tab @code{#(#f #f #f)} @tab no @tab no @tab no
3430 The default settings of @code{break-visibility} depend on the
3431 layout object. The following table shows all the layout objects
3432 of interest which are affected by @code{break-visibility} and the
3433 default setting of this property:
3435 @multitable @columnfractions .3 .3 .4
3437 @headitem Layout object @tab Usual context @tab Default setting
3439 @c omit Ambitus as it appears not to be affected by break-visibility -td
3440 @c @item @code{Ambitus} @tab as specified @tab @code{begin-of-line-visible}
3441 @item @code{BarLine} @tab @code{Score} @tab calculated
3442 @item @code{BarNumber} @tab @code{Score} @tab @code{begin-of-line-visible}
3443 @c omit the following item until it can be explained -td
3444 @c @item @code{BreakAlignGroup} @tab @code{Score} @tab calculated
3445 @item @code{BreathingSign} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3446 @item @code{Clef} @tab @code{Staff} @tab @code{begin-of-line-visible}
3447 @item @code{Custos} @tab @code{Staff} @tab @code{end-of-line-visible}
3448 @item @code{DoublePercentRepeat} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3449 @item @code{KeyCancellation} @tab @code{Staff} @tab @code{begin-of-line-invisible}
3450 @item @code{KeySignature} @tab @code{Staff} @tab @code{begin-of-line-visible}
3451 @c omit LeftEdge until it can be explained -td
3452 @c @item @code{LeftEdge} @tab @code{Score} @tab @code{center-invisible}
3453 @item @code{ClefModifier} @tab @code{Staff} @tab @code{begin-of-line-visible}
3454 @item @code{RehearsalMark} @tab @code{Score} @tab @code{end-of-line-invisible}
3455 @item @code{TimeSignature} @tab @code{Staff} @tab @code{all-visible}
3459 The example below shows the use of the vector form to control the
3460 visibility of bar lines:
3462 @lilypond[quote,verbatim,ragged-right]
3466 % Remove bar line at the end of the current line
3467 \once \override Score.BarLine.break-visibility = ##(#f #t #t)
3474 Although all three components of the vector used to override
3475 @code{break-visibility} must be present, not all of them are
3476 effective with every layout object, and some combinations may
3477 even give errors. The following limitations apply:
3480 @item Bar lines cannot be printed at start of line.
3481 @item A bar number cannot be printed at the start of the first
3482 line unless it is set to be different from 1.
3483 @item Clef -- see below
3484 @item Double percent repeats are either all printed or all
3485 suppressed. Use begin-of line-invisible to print and
3486 all-invisible to suppress.
3487 @item Key signature -- see below
3488 @item ClefModifier -- see below
3491 @node Special considerations
3492 @unnumberedsubsubsec Special considerations
3494 @subsubsubheading Visibility following explicit changes
3496 @cindex key signature, visibility following explicit change
3497 @cindex explicitKeySignatureVisibility
3498 @cindex clef, visibility following explicit change
3499 @cindex explicitClefVisibility
3501 The @code{break-visibility} property controls the visibility of
3502 key signatures and changes of clef only at the start of lines,
3503 i.e. after a break. It has no effect on the visibility of the
3504 key signature or clef following an explicit key change or an
3505 explicit clef change within or at the end of a line. In the
3506 following example the key signature following the explicit change
3507 to B-flat major is still visible, even though @code{all-invisible}
3510 @lilypond[quote,verbatim,ragged-right]
3514 % Try to remove all key signatures
3515 \override Staff.KeySignature.break-visibility = #all-invisible
3524 The visibility of such explicit key signature and clef changes is
3525 controlled by the @code{explicitKeySignatureVisibility} and
3526 @code{explicitClefVisibility} properties. These are the equivalent
3527 of the @code{break-visibility} property and both take a vector of
3528 three booleans or the predefined functions listed above, exactly like
3529 @code{break-visibility}. Both are properties of the Staff context,
3530 not the layout objects themselves, and so they are set using the
3531 @code{\set} command. Both are set by default to @code{all-visible}.
3532 These properties control only the visibility of key signatures and
3533 clefs resulting from explicit changes and do not affect key
3534 signatures and clefs at the beginning of lines;
3535 @code{break-visibility} must still be overridden in the appropriate
3536 object to remove these.
3538 @lilypond[quote,verbatim,ragged-right]
3542 \set Staff.explicitKeySignatureVisibility = #all-invisible
3543 \override Staff.KeySignature.break-visibility = #all-invisible
3551 @subsubsubheading Visibility of cancelling accidentals
3553 To remove the cancelling accidentals printed at an explicit key
3554 change, set the Staff context property @code{printKeyCancellation}
3557 @lilypond[quote,verbatim,ragged-right]
3561 \set Staff.explicitKeySignatureVisibility = #all-invisible
3562 \set Staff.printKeyCancellation = ##f
3563 \override Staff.KeySignature.break-visibility = #all-invisible
3571 With these overrides only the accidentals before the notes remain
3572 to indicate the change of key.
3574 Note that when changing the key to C@tie{}major or A@tie{}minor
3575 the cancelling accidentals would be the @emph{only} indication of
3576 the key change. In this case setting @code{printKeyCancellation} to
3577 @code{#f} has no effect:
3579 @lilypond[quote,verbatim,ragged-right]
3583 \set Staff.explicitKeySignatureVisibility = #all-invisible
3584 \set Staff.printKeyCancellation = ##f
3592 To suppress the cancelling accidentals even when the key is
3593 changed to C@tie{}major or A@tie{}minor, override
3594 the visibility of the @code{KeyCancellation} grob instead:
3596 @lilypond[quote,verbatim,ragged-right]
3600 \set Staff.explicitKeySignatureVisibility = #all-invisible
3601 \override Staff.KeyCancellation.break-visibility = #all-invisible
3609 @c TODO Add visibility of cautionary accidentals before notes
3611 @subsubsubheading Automatic bars
3613 @cindex automaticBars
3614 @cindex bar lines, suppressing
3616 As a special case, the printing of bar lines can also be turned off
3617 by setting the @code{automaticBars} property in the Score context.
3618 If set to @code{#f}, bar lines will not be printed automatically;
3619 they must be explicitly created with a @code{\bar} command. Unlike
3620 the @code{\cadenzaOn} predefined command, measures are still counted.
3621 Bar generation will resume according to that count if this property
3622 is later set to @code{#t}. When set to @code{#f}, line breaks can
3623 occur only at explicit @code{\bar} commands.
3627 @subsubsubheading Transposed clefs
3629 @cindex transposed clefs, visibility of
3630 @cindex visibility of transposed clefs
3631 @cindex clefs, visibility of transposition
3633 The small transposition symbol on transposed clefs is produced by the
3634 @code{ClefModifier} layout object. Its visibility is automatically
3635 inherited from the @code{Clef} object, so it is not necessary to apply
3636 any required @code{break-visibility} overrides to the @code{ClefModifier}
3637 layout objects to suppress transposition symbols for invisible clefs.
3639 For explicit clef changes, the @code{explicitClefVisibility}
3640 property controls both the clef symbol and any transposition symbol
3645 @rlearning{Visibility and color of objects}.
3649 @subsection Line styles
3651 Some performance indications, e.g., @i{rallentando} and
3652 @i{accelerando} and @i{trills} are written as text and are
3653 extended over many measures with lines, sometimes dotted or wavy.
3655 These all use the same routines as the glissando for drawing the
3656 texts and the lines, and tuning their behavior is therefore also
3657 done in the same way. It is done with a spanner, and the routine
3658 responsible for drawing the spanners is
3659 @code{ly:line-spanner::print}. This routine determines the
3660 exact location of the two @i{span points} and draws a line
3661 between them, in the style requested.
3663 Here is an example showing the different line styles available,
3664 and how to tune them.
3666 @lilypond[ragged-right,verbatim,quote]
3669 \once \override Glissando.style = #'dashed-line
3671 \override Glissando.style = #'dotted-line
3673 \override Glissando.style = #'zigzag
3675 \override Glissando.style = #'trill
3680 The locations of the end-points of the spanner are computed
3681 on-the-fly for every graphic object, but it is possible to
3685 @lilypond[ragged-right,verbatim,quote]
3688 \once \override Glissando.bound-details.right.Y = #-2
3693 The value for @code{Y} is set to @w{@code{-2}} for the right end
3694 point. The left side may be similarly adjusted by specifying
3695 @code{left} instead of @code{right}.
3697 If @code{Y} is not set, the value is computed from the vertical
3698 position of the left and right attachment points of the spanner.
3700 Other adjustments of spanners are possible, for details, see
3703 @node Rotating objects
3704 @subsection Rotating objects
3706 Both layout objects and elements of markup text can be rotated by
3707 any angle about any point, but the method of doing so differs.
3710 * Rotating layout objects::
3714 @node Rotating layout objects
3715 @unnumberedsubsubsec Rotating layout objects
3717 @cindex rotating objects
3718 @cindex objects, rotating
3720 All layout objects which support the @code{grob-interface} can be
3721 rotated by setting their @code{rotation} property. This takes a
3722 list of three items: the angle of rotation counter-clockwise,
3723 and the x and y coordinates of the point relative to the object's
3724 reference point about which the rotation is to be performed. The
3725 angle of rotation is specified in degrees and the coordinates in
3728 The angle of rotation and the coordinates of the rotation point must
3729 be determined by trial and error.
3731 @cindex hairpins, angled
3732 @cindex angled hairpins
3734 There are only a few situations where the rotation of layout
3735 objects is useful; the following example shows one situation where
3738 @lilypond[quote,fragment,verbatim]
3740 \override Hairpin.rotation = #'(20 -1 0)
3744 @node Rotating markup
3745 @unnumberedsubsubsec Rotating markup
3747 All markup text can be rotated to lie at any angle by prefixing it
3748 with the @code{\rotate} command. The command takes two arguments:
3749 the angle of rotation in degrees counter-clockwise and the text to
3750 be rotated. The extents of the text are not rotated: they take
3751 their values from the extremes of the x and y coordinates of the
3752 rotated text. In the following example the
3753 @code{outside-staff-priority} property for text is set to @code{#f}
3754 to disable the automatic collision avoidance, which would push some
3755 of the text too high.
3757 @lilypond[quote,fragment,verbatim]
3758 \override TextScript.outside-staff-priority = ##f
3759 g4^\markup { \rotate #30 "a G" }
3760 b^\markup { \rotate #30 "a B" }
3761 des'^\markup { \rotate #30 "a D-Flat" }
3762 fis'^\markup { \rotate #30 "an F-Sharp" }
3765 @node Advanced tweaks
3766 @section Advanced tweaks
3768 This section discusses various approaches to fine tuning the
3769 appearance of the printed score.
3772 * Aligning objects::
3773 * Vertical grouping of grobs::
3774 * Modifying stencils::
3775 * Modifying shapes::
3776 * Modifying broken spanners::
3777 * Unpure-pure containers::
3782 @rlearning{Tweaking output},
3783 @rlearning{Other sources of information}.
3786 @ref{Explaining the Internals Reference},
3787 @ref{Modifying properties}.
3790 @rextend{Interfaces for programmers}.
3793 @file{scm/define-grobs.scm}.
3796 @rlsr{Tweaks and overrides}.
3798 Internals Reference:
3799 @rinternals{All layout objects}.
3802 @node Aligning objects
3803 @subsection Aligning objects
3805 Graphical objects which support the @code{self-alignment-interface}
3806 and/or the @code{side-position-interface} can be aligned to a previously
3807 placed object in a variety of ways. For a list of these objects, see
3808 @rinternals{self-alignment-interface} and @rinternals{side-position-interface}.
3810 All graphical objects have a reference point, a horizontal extent and a
3811 vertical extent. The horizontal extent is a pair of numbers
3812 giving the displacements from the reference point of the left and
3813 right edges, displacements to the left being negative. The vertical
3814 extent is a pair of numbers giving the displacement from the reference
3815 point to the bottom and top edges, displacements down being negative.
3817 An object's position on a staff is given by the values of the
3818 @code{X-offset} and @code{Y-offset} properties. The value of
3819 @code{X-offset} gives the displacement from the X coordinate of
3820 the reference point of the parent object, and the value of
3821 @code{Y-offset} gives the displacement from the center line of the
3822 staff. The values of @code{X-offset} and @code{Y-offset} may
3823 be set directly or may be set to be calculated by procedures in order
3824 to achieve alignment with the parent object.
3826 @warning{Many objects have special positioning considerations which
3827 cause any setting of @code{X-offset} or @code{Y-offset} to be
3828 ignored or modified, even though the object supports the
3829 @code{self-alignment-interface}. Overriding the @code{X-offset}
3830 or @code{Y-offset} properties to a fixed value causes the respective
3831 @code{self-alignment} property to be disregarded.}
3833 For example, an accidental can be repositioned vertically by setting
3834 @code{Y-offset} but any changes to @code{X-offset} have no effect.
3836 Rehearsal marks may be aligned with breakable objects such as bar
3837 lines, clef symbols, time signature symbols and key signatures. There
3838 are special properties to be found in the @code{break-aligned-interface}
3839 for positioning rehearsal marks on such objects.
3843 @ref{Using the break-alignable-interface}.
3846 @rextend{Callback functions}.
3849 * Setting X-offset and Y-offset directly::
3850 * Using the side-position-interface::
3851 * Using the self-alignment-interface::
3852 * Using the break-alignable-interface::
3855 @node Setting X-offset and Y-offset directly
3856 @unnumberedsubsubsec Setting @code{X-offset} and @code{Y-offset} directly
3858 Numerical values may be given to the @code{X-offset} and @code{Y-offset}
3859 properties of many objects. The following example shows three
3860 notes with the default fingering position and the positions with @code{X-offset}
3861 and @code{Y-offset} modified.
3863 @lilypond[verbatim,fragment,quote]
3870 -\tweak X-offset #-1
3877 @node Using the side-position-interface
3878 @unnumberedsubsubsec Using the @code{side-position-interface}
3880 An object which supports the @code{side-position-interface} can be
3881 placed next to its parent object so that
3882 the specified edges of the two objects touch. The object may be
3883 placed above, below, to the right or to the left of the parent.
3884 The parent cannot be specified; it is determined by the order of
3885 elements in the input stream. Most objects have the associated
3886 note head as their parent.
3888 The values of the @code{side-axis} and @code{direction} properties
3889 determine where the object is to be placed, as follows:
3891 @c TODO add an example of each to the table
3893 @multitable @columnfractions .3 .3 .3
3894 @headitem @code{side-axis} @tab @code{direction} @tab
3895 @headitem property @tab property @tab Placement
3897 @item @code{0} @tab @code{-1} @tab left
3898 @item @code{0} @tab @code{1} @tab right
3899 @item @code{1} @tab @code{-1} @tab below
3900 @item @code{1} @tab @code{1} @tab above
3904 When @code{side-axis} is @code{0}, @code{X-offset} should be set to
3905 the procedure @code{ly:side-position-interface::x-aligned-side}.
3906 This procedure will return the correct value of @code{X-offset} to
3907 place the object to the left or right side of the parent according
3908 to value of @code{direction}.
3910 When @code{side-axis} is @code{1}, @code{Y-offset} should be set to
3911 the procedure @code{ly:side-position-interface::y-aligned-side}.
3912 This procedure will return the correct value of @code{Y-offset} to
3913 place the object to the top or bottom of the parent according
3914 to value of @code{direction}.
3916 @c TODO Add examples
3918 @node Using the self-alignment-interface
3919 @unnumberedsubsubsec Using the @code{self-alignment-interface}
3921 @subsubsubheading Self-aligning objects horizontally
3923 The horizontal alignment of an object which supports the
3924 @code{self-alignment-interface} is controlled by the value of
3925 the @code{self-alignment-X} property, provided the object's
3926 @code{X-offset} property is set to
3927 @code{ly:self-alignment-interface::x-aligned-on-self}.
3928 @code{self-alignment-X} may be given any
3929 real value, in units of half the total X extent of the
3930 object. Negative values move the object to the right, positive
3931 to the left. A value of @code{0} centers the object on the
3932 reference point of its parent, a value of @w{@code{-1}} aligns the
3933 left edge of the object on the reference point of its parent,
3934 and a value of @code{1} aligns the right edge of the object on the
3935 reference point of its parent. The symbols @code{LEFT},
3936 @code{CENTER}, and @code{RIGHT} may be used instead of the values
3937 @w{@code{-1}}, @code{0}, and @code{1}, respectively.
3939 Normally the @code{\override} command would be used to modify the
3940 value of @code{self-alignment-X}, but the @code{\tweak} command
3941 can be used to separately align several annotations on a single
3944 @lilypond[quote,verbatim,fragment]
3946 -\tweak self-alignment-X #-1
3948 -\tweak self-alignment-X #0
3950 -\tweak self-alignment-X #RIGHT
3952 -\tweak self-alignment-X #-2.5
3953 ^"aligned further to the right"
3956 @subsubsubheading Self-aligning objects vertically
3958 Objects may be aligned vertically in an analogous way to aligning
3959 them horizontally if the @code{Y-offset} property is set to
3960 @code{ly:self-alignment-interface::y-aligned-on-self}. However,
3961 other mechanisms are often involved in vertical alignment: the
3962 value of @code{Y-offset} is just one variable taken into account.
3963 This may make adjusting the value of some objects tricky.
3964 The units are just half the vertical extent of the object, which
3965 is usually quite small, so quite large numbers may be required.
3966 A value of @w{@code{-1}} aligns the lower edge of the object with
3967 the reference point of the parent object, a value of @code{0}
3968 aligns the center of the object with the reference point of the
3969 parent, and a value of @code{1} aligns the top edge of the object
3970 with the reference point of the parent. The symbols @code{DOWN},
3971 @code{CENTER}, and @code{UP} may be substituted for @w{@code{-1}},
3972 @code{0}, and @code{1}, respectively.
3974 @subsubsubheading Self-aligning objects in both directions
3976 By setting both @code{X-offset} and @code{Y-offset}, an object may
3977 be aligned in both directions simultaneously.
3979 The following example shows how to adjust a fingering mark so
3980 that it nestles close to the note head.
3982 @lilypond[quote,verbatim,fragment]
3984 -\tweak self-alignment-X #0.5 % move horizontally left
3985 -\tweak Y-offset #ly:self-alignment-interface::y-aligned-on-self
3986 -\tweak self-alignment-Y #-1 % move vertically up
3991 @unnumberedsubsubsec Using the @code{aligned-on-parent} procedures
3993 @c Cannot document as they do not seem to operate consistently on all objects -td
3994 @c TODO investigate further
3996 The @code{aligned-on-parent} procedures are used in the same way
3997 as the @code{aligned-on-self} procedures, they difference being
3998 that they permit an object to be aligned with the @emph{edges} of
3999 the parent rather than the parent's reference point. The following
4000 example shows the difference:
4004 @lilypond[verbatim,quote]
4010 @unnumberedsubsubsec Using the @code{centered-on-parent} procedures
4012 @c Cannot document as they do not seem to operate consistently on all objects -td
4013 @c TODO investigate further
4017 @c TODO The align-interface, BassFigureAlignment and VerticalAlignment
4019 @node Using the break-alignable-interface
4020 @unnumberedsubsubsec Using the @code{break-alignable-interface}
4022 @cindex align to objects
4023 @cindex break-align-symbols
4025 Rehearsal marks and bar numbers may be aligned with notation
4026 objects other than bar lines. These objects include @code{ambitus},
4027 @code{breathing-sign}, @code{clef}, @code{custos}, @code{staff-bar},
4028 @code{left-edge}, @code{key-cancellation}, @code{key-signature}, and
4029 @code{time-signature}.
4031 Each type of object has its own default reference point, to which
4032 rehearsal marks are aligned:
4034 @lilypond[verbatim,quote,fragment]
4035 % The rehearsal mark will be aligned to the right edge of the Clef
4036 \override Score.RehearsalMark.break-align-symbols = #'(clef)
4041 % The rehearsal mark will be aligned to the left edge of the Time Signature
4042 \override Score.RehearsalMark.break-align-symbols = #'(time-signature)
4048 % The rehearsal mark will be centered above the Breath Mark
4049 \override Score.RehearsalMark.break-align-symbols = #'(breathing-sign)
4058 A list of possible target alignment objects may be specified. If
4059 some of the objects are invisible at that point due to the setting
4060 of @code{break-visibility} or the explicit visibility settings for
4061 keys and clefs, the rehearsal mark or bar number is aligned to the
4062 first object in the list which is visible. If no objects in the
4063 list are visible the object is aligned to the bar line. If the bar
4064 line is invisible the object is aligned to the place where the bar
4067 @lilypond[verbatim,quote,fragment]
4068 % The rehearsal mark will be aligned to the right edge of the Key Signature
4069 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4074 % The rehearsal mark will be aligned to the right edge of the Clef
4075 \set Staff.explicitKeySignatureVisibility = #all-invisible
4076 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4081 % The rehearsal mark will be centered above the Bar Line
4082 \set Staff.explicitKeySignatureVisibility = #all-invisible
4083 \set Staff.explicitClefVisibility = #all-invisible
4084 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4091 The alignment of the rehearsal mark relative to the notation object
4092 can be changed, as shown in the following example. In a score with
4093 multiple staves, this setting should be done for all the staves.
4095 @lilypond[verbatim,quote,fragment]
4096 % The RehearsalMark will be aligned with the right edge of the Key Signature
4097 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4103 % The RehearsalMark will be centered above the Key Signature
4104 \once \override Score.KeySignature.break-align-anchor-alignment = #CENTER
4108 % The RehearsalMark will be aligned with the left edge of the Key Signature
4109 \once \override Score.KeySignature.break-align-anchor-alignment = #LEFT
4115 The rehearsal mark can also be offset to the right or left of the left
4116 edge by an arbitrary amount. The units are staff-spaces:
4118 @lilypond[verbatim,quote,fragment]
4119 % The RehearsalMark will be aligned with the left edge of the Key Signature
4120 % and then shifted right by 3.5 staff-spaces
4121 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4122 \once \override Score.KeySignature.break-align-anchor = #3.5
4126 % The RehearsalMark will be aligned with the left edge of the Key Signature
4127 % and then shifted left by 2 staff-spaces
4128 \once \override Score.KeySignature.break-align-anchor = #-2
4135 @node Vertical grouping of grobs
4136 @subsection Vertical grouping of grobs
4138 @c TODO Expand this section
4140 The VerticalAlignment and VerticalAxisGroup grobs work together.
4141 VerticalAxisGroup groups together different grobs like Staff, Lyrics,
4142 etc. VerticalAlignment then vertically aligns the different grobs
4143 grouped together by VerticalAxisGroup. There is usually only one
4144 VerticalAlignment per score but every Staff, Lyrics, etc. has its own
4148 @node Modifying stencils
4149 @subsection Modifying stencils
4151 All layout objects have a @code{stencil} property which is part of
4152 the @code{grob-interface}. By default, this property is usually
4153 set to a function specific to the object that is tailor-made to
4154 render the symbol which represents it in the output. For example,
4155 the standard setting for the @code{stencil} property of the
4156 @code{MultiMeasureRest} object is @code{ly:multi-measure-rest::print}.
4158 The standard symbol for any object can be replaced by modifying the
4159 @code{stencil} property to reference a different, specially-written,
4160 procedure. This requires a high level of knowledge of the internal
4161 workings of LilyPond, but there is an easier way which can often
4162 produce adequate results.
4164 This is to set the @code{stencil} property to the procedure which
4165 prints text -- @code{ly:text-interface::print} -- and to add a
4166 @code{text} property to the object which is set to contain the
4167 markup text which produces the required symbol. Due to the
4168 flexibility of markup, much can be achieved -- see in particular
4169 @ref{Graphic notation inside markup}.
4171 The following example demonstrates this by changing the note head
4172 symbol to a cross within a circle.
4174 @lilypond[verbatim,quote]
4176 \once \override NoteHead.stencil = #ly:text-interface::print
4177 \once \override NoteHead.text = \markup {
4179 \halign #-0.7 \draw-circle #0.85 #0.2 ##f
4180 \musicglyph #"noteheads.s2cross"
4188 Any of the glyphs in the feta Font can be supplied to the
4189 @code{\musicglyph} markup command -- see @ref{The Feta font}.
4191 @c TODO Add inserting eps files or ref to later
4193 @c TODO Add inserting Postscript or ref to later
4197 @ref{Graphic notation inside markup},
4198 @ref{Formatting text},
4199 @ref{Text markup commands},
4200 @ref{The Feta font}.
4203 @node Modifying shapes
4204 @subsection Modifying shapes
4207 * Modifying ties and slurs::
4210 @node Modifying ties and slurs
4211 @unnumberedsubsubsec Modifying ties and slurs
4213 @cindex slurs, modifying
4214 @cindex ties, modifying
4215 @cindex Bézier curves, control points
4216 @cindex control points, Bézier curves
4218 @code{Tie}s, @code{Slur}s, @code{PhrasingSlur}s,
4219 @code{LaissezVibrerTie}s and @code{RepeatTie}s are all drawn as
4220 third-order Bézier curves. If the shape of the tie or slur which
4221 is calculated automatically is not optimum, the shape may be
4222 modified manually in two ways:
4226 by specifying the displacements to be made to the control points
4227 of the automatically calculated Bézier curve, or
4230 by explicitly specifying the positions of the four control points
4231 required to define the wanted curve.
4234 Both methods are explained below. The first method is more suitable
4235 if only slight adjustments to the curve are required; the second may
4236 be better for creating curves which are related to just a single
4239 @subsubsubheading Cubic Bézier curves
4241 Third-order or cubic Bézier curves are defined by four control
4242 points. The first and fourth control points are precisely the
4243 starting and ending points of the curve. The intermediate two
4244 control points define the shape. Animations showing how the curve
4245 is drawn can be found on the web, but the following description
4246 may be helpful. The curve starts from the first control point
4247 heading directly towards the second, gradually bending over to
4248 head towards the third and continuing to bend over to head towards
4249 the fourth, arriving there travelling directly from the third
4250 control point. The curve is entirely contained in the
4251 quadrilateral defined by the four control points. Translations,
4252 rotations and scaling of the control points all result in exactly
4253 the same operations on the curve.
4255 @subsubsubheading Specifying displacements from current control points
4257 @cindex shaping slurs and ties
4260 In this example the automatic placement of the tie is not optimum,
4261 and @code{\tieDown} would not help.
4263 @lilypond[verbatim,quote]
4267 \relative { r4 <g' c,> <g c,> <g c,> }
4271 Adjusting the control points of the tie with @code{\shape} allows
4272 the collisions to be avoided.
4274 The syntax of @code{\shape} is
4277 [-]@code{\shape} @var{displacements} @var{item}
4280 This will reposition the control-points of @var{item} by the amounts
4281 given by @var{displacements}. The @var{displacements} argument is a
4282 list of number pairs or a list of such lists. Each element of a pair
4283 represents the displacement of one of the coordinates of a
4284 control-point. If @var{item} is a string, the result is
4285 @code{\once\override} for the specified grob type. If @var{item} is
4286 a music expression, the result is the same music expression with an
4287 appropriate tweak applied.
4289 In other words, the @code{\shape} function can act as either a
4290 @code{\once\override} command or a @code{\tweak} command depending
4291 on whether the @var{item} argument is a grob name, like @qq{Slur},
4292 or a music expression, like @qq{(}. The @var{displacements} argument
4293 specifies the displacements of the four control points as a list of
4294 four pairs of (dx . dy) values in units of staff-spaces (or a list
4295 of such lists if the curve has more than one segment).
4297 The leading hyphen is required if and only if the @code{\tweak} form
4300 So, using the same example as above and the @code{\once\override}
4301 form of @code{\shape}, this will raise the tie by half a staff-space:
4303 @lilypond[verbatim,quote]
4306 \shape #'((0 . 0.5) (0 . 0.5) (0 . 0.5) (0 . 0.5)) Tie
4310 \relative { r4 <g' c,> <g c,> <g c,> }
4314 This positioning of the tie is better, but maybe it should be raised
4315 more in the center. The following example does this, this time using
4316 the alternative @code{\tweak} form:
4318 @lilypond[verbatim,quote]
4321 e'1-\shape #'((0 . 0.5) (0 . 1) (0 . 1) (0 . 0.5)) ~ e'
4324 \relative { r4 <g' c,> <g c,> <g c,> }
4328 Changes to the horizontal positions of the control points may be made
4329 in the same way, and two different curves starting at the same
4330 musical moment may also be shaped:
4332 @lilypond[verbatim,quote,ragged-right]
4334 c''8(\( a) a'4 e c\)
4335 \shape #'((0.7 . -0.4) (0.5 . -0.4) (0.3 . -0.3) (0 . -0.2)) Slur
4336 \shape #'((0 . 0) (0 . 0.5) (0 . 0.5) (0 . 0)) PhrasingSlur
4341 The @code{\shape} function can also displace the control points of
4342 curves which stretch across line breaks. Each piece of the broken
4343 curve can be given its own list of offsets. If changes to a
4344 particular segment are not needed, the empty list can serve as a
4345 placeholder. In this example the line break makes the single slur
4348 @lilypond[verbatim,quote,ragged-right]
4356 Changing the shapes of the two halves of the slur makes it clearer
4357 that the slur continues over the line break:
4359 @lilypond[verbatim,quote,ragged-right]
4360 % () may be used as a shorthand for ((0 . 0) (0 . 0) (0 . 0) (0 . 0))
4361 % if any of the segments does not need to be changed
4364 (( 0 . 0) (0 . 0) (0 . 0) (0 . 1))
4365 ((0.5 . 1.5) (1 . 0) (0 . 0) (0 . -1.5))
4373 If an S-shaped curve is required the control points must always be
4374 adjusted manually --- LilyPond will never select such shapes
4377 @lilypond[verbatim,quote]
4379 c8( e b-> f d' a e-> g)
4380 \shape #'((0 . -1) (5.5 . -0.5) (-5.5 . -10.5) (0 . -5.5)) PhrasingSlur
4381 c8\( e b-> f d' a e-> g\)
4385 @subsubsubheading Specifying control points explicitly
4387 The coordinates of the Bézier control points are specified in units
4388 of staff-spaces. The X@tie{}coordinate is relative to the reference
4389 point of the note to which the tie or slur is attached, and the
4390 Y@tie{}coordinate is relative to the staff center line. The
4391 coordinates are specified as a list of four pairs of decimal numbers
4392 (reals). One approach is to estimate the coordinates of the two
4393 end points, and then guess the two intermediate points. The optimum
4394 values are then found by trial and error. Be aware that these values
4395 may need to be manually adjusted if any further changes are made to
4396 the music or the layout.
4398 One situation where specifying the control points explicitly is
4399 preferable to specifying displacements is when they need to be
4400 specified relative to a single note. Here is an example of this.
4401 It shows one way of indicating a slur extending into alternative
4402 sections of a volta repeat.
4404 @lilypond[verbatim,quote]
4407 \repeat volta 3 { c4 d( e f }
4412 % create a slur and move it to a new position
4413 % the <> is just an empty chord to carry the slur termination
4414 -\tweak control-points #'((-2 . 3.8) (-1 . 3.9) (0 . 4) (1 . 3.4)) ( <> )
4419 % create a slur and move it to a new position
4420 -\tweak control-points #'((-2 . 3) (-1 . 3.1) (0 . 3.2) (1 . 2.4)) ( <> )
4428 It is not possible to modify shapes of ties or slurs by changing
4429 the @code{control-points} property if there are multiple ties or slurs
4430 at the same musical moment -- the @code{\tweak} command will also not
4431 work in this case. However, the @code{tie-configuration} property of
4432 @code{TieColumn} can be overridden to set start line and direction as
4436 Internals Reference:
4437 @rinternals{TieColumn}.
4440 @node Modifying broken spanners
4441 @subsection Modifying broken spanners
4444 * Using alterBroken::
4447 @node Using alterBroken
4448 @unnumberedsubsubsec Using @code{\alterBroken}
4450 @cindex spanners, modifying
4451 @cindex broken spanners, modifying
4452 @funindex \alterBroken
4454 When a spanner crosses a line break or breaks, each piece
4455 inherits the attributes of the original spanner. Thus, ordinary
4456 tweaking of a broken spanner applies the same modifications to
4457 each of its segments. In the example below, overriding
4458 @code{thickness} affects the slur on either side of the line
4461 @lilypond[verbatim,quote,ragged-right]
4464 \once\override Slur.thickness = 10
4471 Independently modifying the appearance of individual pieces
4472 of a broken spanner is possible with the @code{\alterBroken}
4473 command. This command can produce either an @code{\override}
4474 or a @code{\tweak} of a spanner property.
4476 The syntax for @code{\alterBroken} is
4479 [-]@code{\alterBroken} @var{property} @var{values} @var{item}
4482 The argument @var{values} is a list of values, one for each
4483 broken piece. If @var{item} is a grob name like @code{Slur} or
4484 @code{Staff.PianoPedalBracket}, the result is an @code{\override}
4485 of the specified grob type. If @var{item} is a music expression
4486 such as @qq{(} or @qq{[} the result is the same music expression
4487 with an appropriate tweak applied.
4489 The leading hyphen must be used with the @code{\tweak} form. Do
4490 not add it when @code{\alterBroken} is used as an
4493 In its @code{\override} usage, @code{\alterBroken} may be
4494 prefaced by @code{\once} or @code{\temporary} and reverted by
4495 using @code{\revert} with @var{property}.
4497 The following code applies an independent @code{\override} to
4498 each of the slur segments in the previous example:
4500 @lilypond[verbatim,quote,ragged-right]
4503 \alterBroken thickness #'(10 1) Slur
4510 The @code{\alterBroken} command may be used with any spanner
4511 object, including @code{Tie}, @code{PhrasingSlur}, @code{Beam}
4512 and @code{TextSpanner}. For example, an editor preparing a
4513 scholarly edition may wish to indicate the absence of part of a
4514 phrasing slur in a source by dashing only the segment which has
4515 been added. The following example illustrates how this can be
4516 done, in this case using the @code{\tweak} form of the command:
4518 @lilypond[verbatim,quote,ragged-right]
4519 % The empty list is conveniently used below, because it is the
4520 % default setting of dash-definition, resulting in a solid curve.
4522 c''2-\alterBroken dash-definition #'(() ((0 1.0 0.4 0.75))) \(e
4528 It is important to understand that @code{\alterBroken} will set
4529 each piece of a broken spanner to the corresponding value in
4530 @var{values}. When there are fewer values than pieces, any
4531 additional piece will be assigned the empty list. This may lead
4532 to undesired results if the layout property is not set to the
4533 empty list by default. In such cases, each segment should be
4534 assigned an appropriate value.
4537 Line breaks may occur in different places following changes in
4538 layout. Settings chosen for @code{\alterBroken} may be unsuitable
4539 for a spanner that is no longer broken or is split into more
4540 segments than before. Explicit use of @code{\break} can guard
4541 against this situation.
4543 The @code{\alterBroken} command is ineffective for spanner
4544 properties accessed before line-breaking such as
4549 @rextend{Difficult tweaks}.
4552 @node Unpure-pure containers
4553 @subsection Unpure-pure containers
4555 @cindex Scheme, pure containers
4556 @cindex Scheme, unpure containers
4557 @cindex pure containers, Scheme
4558 @cindex unpure containers, Scheme
4559 @cindex horizontal spacing, overriding
4561 Unpure-pure containers are useful for overriding @emph{Y-axis} spacing
4562 calculations - specifically @code{Y-offset} and @code{Y-extent} - with a
4563 Scheme function instead of a literal (i.e. a number or pair).
4565 For certain grobs, the @code{Y-extent} is based on the @code{stencil}
4566 property, overriding the stencil property of one of these will
4567 require an additional @code{Y-extent} override with an unpure-pure
4568 container. When a function overrides a @code{Y-offset} and/or
4569 @code{Y-extent} it is assumed that this will trigger line breaking
4570 calculations too early during compilation. So the function is not
4571 evaluated at all (usually returning a value of @samp{0} or
4572 @samp{'(0 . 0)}) which can result in collisions. A @q{pure} function
4573 will not affect properties, objects or grob suicides and therefore will
4574 always have its Y-axis-related evaluated correctly.
4576 Currently, there are about thirty functions that are already considered
4577 @q{pure} and Unpure-pure containers are a way to set functions not on
4578 this list as @q{pure}. The @q{pure} function is evaluated @emph{before}
4579 any line-breaking and so the horizontal spacing can be adjusted
4580 @q{in time}. The @q{unpure} function is then evaluated @emph{after}
4583 @warning{As it is difficult to always know which functions are on this
4584 list we recommend that any @q{pure} functions you create do not use
4585 @code{Beam} or @code{VerticalAlignment} grobs.}
4587 An unpure-pure container is constructed as follows;
4589 @code{(ly:make-unpure-pure-container f0 f1)}
4591 where @code{f0} is a function taking @var{n} arguments (@var{n >= 1})
4592 and the first argument must always be the grob. This is the function
4593 that gives the actual result. @var{f1} is the function being labeled
4594 as @q{pure} that takes @var{n + 2} arguments. Again, the first argument
4595 must always still be the grob but the second and third are @q{start}
4596 and @q{end} arguments.
4598 @var{start} and @var{end} are, for all intents and purposes, dummy
4599 values that only matter for @code{Spanners} (i.e @code{Hairpin} or
4600 @code{Beam}), that can return different height estimations based on a
4601 starting and ending column.
4603 The rest are the other arguments to the first function (which
4604 may be none if @var{n = 1}).
4606 The results of the second function are used as an approximation of the
4607 value needed which is then used by the first function to get the real
4608 value which is then used for fine-tuning much later during the spacing
4611 @lilypond[verbatim,quote,ragged-right]
4612 #(define (square-line-circle-space grob)
4613 (let* ((pitch (ly:event-property (ly:grob-property grob 'cause) 'pitch))
4614 (notename (ly:pitch-notename pitch)))
4615 (if (= 0 (modulo notename 2))
4616 (make-circle-stencil 0.5 0.0 #t)
4617 (make-filled-box-stencil '(0 . 1.0)
4620 squareLineCircleSpace = {
4621 \override NoteHead.stencil = #square-line-circle-space
4624 smartSquareLineCircleSpace = {
4625 \squareLineCircleSpace
4626 \override NoteHead.Y-extent =
4627 #(ly:make-unpure-pure-container
4628 ly:grob::stencil-height
4629 (lambda (grob start end) (ly:grob::stencil-height grob)))
4632 \new Voice \with { \remove "Stem_engraver" }
4634 \squareLineCircleSpace
4636 \smartSquareLineCircleSpace
4641 In the first measure, without the unpure-pure container, the spacing
4642 engine does not know the width of the note head and lets it collide with
4643 the accidentals. In the second measure, with unpure-pure containers,
4644 the spacing engine knows the width of the note heads and avoids the
4645 collision by lengthening the line accordingly.
4647 Usually for simple calculations nearly-identical functions for
4648 both the @q{unpure} and @q{pure} parts can be used, by only
4649 changing the number of arguments passed to, and the scope of, the
4650 function. This use case is frequent enough that
4651 @code{ly:make-unpure-pure-container} constructs such a second
4652 function by default when called with only one function argument.
4654 @warning{If a function is labeled as @q{pure} and it turns out not to
4655 be, the results can be unexpected.}
4658 @node Using music functions
4659 @section Using music functions
4661 @c TODO -- add @seealso, etc. to these subsections
4663 Where tweaks need to be reused with different music expressions,
4664 it is often convenient to make the tweak part of a @emph{music
4665 function}. In this section, we discuss only @emph{substitution}
4666 functions, where the object is to substitute a variable into a
4667 piece of LilyPond input code. Other more complex functions are
4668 described in @rextend{Music functions}.
4671 * Substitution function syntax::
4672 * Substitution function examples::
4675 @node Substitution function syntax
4676 @subsection Substitution function syntax
4678 Making a function that substitutes a variable into LilyPond
4679 code is easy. The general form of these functions is
4683 #(define-music-function
4684 (@var{arg1} @var{arg2} @dots{})
4685 (@var{type1?} @var{type2?} @dots{})
4687 @var{@dots{}music@dots{}}
4694 @multitable @columnfractions .33 .66
4695 @item @code{@var{argN}}
4696 @tab @var{n}th argument
4698 @item @code{@var{typeN?}}
4699 @tab a scheme @emph{type predicate} for which @code{@var{argN}}
4700 must return @code{#t}.
4702 @item @code{@var{@dots{}music@dots{}}}
4703 @tab normal LilyPond input, using @code{$} (in places where only
4704 Lilypond constructs are allowed) or @code{#} (to use it as a Scheme
4705 value or music function argument or music inside of music lists) to
4710 The list of type predicates is required. Some of the most common
4711 type predicates used in music functions are:
4715 cheap-list? @emph{(use instead of }@q{list?}@emph{ for faster processing)}
4727 For a list of available type predicates, see
4728 @ref{Predefined type predicates}. User-defined type predicates
4733 @ref{Predefined type predicates}.
4736 @rextend{Music functions}.
4739 @file{lily/music-scheme.cc},
4741 @file{scm/lily.scm}.
4744 @node Substitution function examples
4745 @subsection Substitution function examples
4747 This section introduces some substitution function examples.
4748 These are not intended to be exhaustive, but rather to demonstrate
4749 some of the possibilities of simple substitution functions.
4751 In the first example, a function is defined that simplifies
4752 setting the padding of a TextScript:
4754 @lilypond[quote,verbatim,ragged-right]
4756 #(define-music-function
4760 \once \override TextScript.padding = #padding
4764 c''4^"piu mosso" b a b
4766 c4^"piu mosso" b a b
4768 c4^"piu mosso" b a b
4772 In addition to numbers, we can use music expressions such
4773 as notes for arguments to music functions:
4775 @lilypond[quote,verbatim,ragged-right]
4777 #(define-music-function
4781 \tweak NoteHead.stencil #ly:text-interface::print
4782 \tweak NoteHead.text
4783 \markup \musicglyph #"custodes.mensural.u0"
4784 \tweak Stem.stencil ##f
4788 \relative { c'4 d e f \custosNote g }
4792 Both of those functions are simple single expressions where only
4793 the last element of a function call or override is missing. For
4794 those particular function definitions, there is a simpler
4795 alternative syntax, namely just writing out the constant part of
4796 the expression and replacing its final missing element with
4799 @lilypond[quote,verbatim,ragged-right]
4801 \once \override TextScript.padding = \etc
4804 c''4^"piu mosso" b a b
4806 c4^"piu mosso" b a b
4808 c4^"piu mosso" b a b
4812 @lilypond[quote,verbatim,ragged-right]
4814 \tweak NoteHead.stencil #ly:text-interface::print
4815 \tweak NoteHead.text
4816 \markup \musicglyph #"custodes.mensural.u0"
4817 \tweak Stem.stencil ##f
4820 \relative { c'4 d e f \custosNote g }
4824 Substitution functions with multiple arguments can be defined:
4826 @lilypond[quote,verbatim,ragged-right]
4828 #(define-music-function
4832 \once \override Score.MetronomeMark.padding = #padding
4833 \tempo \markup { \bold #tempotext }
4837 \tempo \markup { "Low tempo" }
4839 \tempoPadded #4.0 "High tempo"
4844 @c TODO: add appropriate @@ref's here.