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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: just one of the
540 @code{Voice} contexts in a @code{Staff} context or in a
541 @code{<<@dots{}>>} construct will always persist to the end of the
542 enclosing @code{Staff} context or @code{<<@dots{}>>} construct, even
543 though there may be periods when it has nothing to do. The context
544 to persist in this way will be the first one encountered in the
545 first enclosed @code{@{@dots{}@}} construct, ignoring any in enclosed
546 @code{<<@dots{}>>} constructs.
548 Any context can be kept alive by ensuring it has something to do at
549 every musical moment. @code{Staff} contexts are kept alive by
550 ensuring one of their voices is kept alive. One way of doing this
551 is to add spacer rests to a voice in parallel with the real music.
552 These need to be added to every @code{Voice} context which needs to
553 be kept alive. If several voices are to be used sporadically it is
554 safest to keep them all alive rather than attempting to rely on the
555 exceptions mentioned above.
557 In the following example, both voice A and voice B are kept alive
558 in this way for the duration of the piece:
560 @lilypond[quote,verbatim]
561 musicA = \relative { d''4 d d d }
562 musicB = \relative { g'4 g g g }
565 \new Voice = "A" { s1*5 } % Keep Voice "A" alive for 5 bars
566 \new Voice = "B" { s1*5 } % Keep Voice "B" alive for 5 bars
571 \context Voice = "A" {
575 \context Voice = "B" {
579 \context Voice = "A" { \musicA }
580 \context Voice = "B" { \musicB }
581 \context Voice = "A" { \musicA }
592 @cindex lyrics, aligning with sporadic melody
594 The following example shows how a sporadic melody line with lyrics
595 might be written using this approach. In a real situation the
596 melody and accompaniment would consist of several different
599 @lilypond[quote,verbatim]
600 melody = \relative { a'4 a a a }
601 accompaniment = \relative { d'4 d d d }
602 words = \lyricmode { These words fol -- low the mel -- o -- dy }
605 \new Staff = "music" {
607 \new Voice = "melody" {
609 s1*4 % Keep Voice "melody" alive for 4 bars
612 \new Voice = "accompaniment" {
617 \context Voice = "melody" { \melody }
618 \context Voice = "accompaniment" { \accompaniment }
620 \context Voice = "accompaniment" { \accompaniment }
622 \context Voice = "melody" { \melody }
623 \context Voice = "accompaniment" { \accompaniment }
628 \new Lyrics \with { alignAboveContext = #"music" }
629 \lyricsto "melody" { \words }
634 An alternative way, which may be better in many circumstances, is
635 to keep the melody line alive by simply including spacer notes to
636 line it up correctly with the accompaniment:
638 @lilypond[quote,verbatim]
645 accompaniment = \relative {
651 words = \lyricmode { These words fol -- low the mel -- o -- dy }
655 \new Staff = "music" {
657 \new Voice = "melody" {
661 \new Voice = "accompaniment" {
667 \new Lyrics \with { alignAboveContext = #"music" }
668 \lyricsto "melody" { \words }
674 @node Modifying context plug-ins
675 @subsection Modifying context plug-ins
677 @c TODO Should this be Modifying engravers or Modifying contexts?
679 Notation contexts (like @code{Score} and @code{Staff}) not only store
680 properties, they also contain plug-ins called @q{engravers} that create
681 notation elements. For example, the @code{Voice} context contains a
682 @code{Note_heads_engraver} and the @code{Staff} context contains a
685 For a full a description of each plug-in, see
687 @rinternals{Engravers and Performers}.
690 Internals Reference @expansion{} Translation @expansion{} Engravers.
692 Every context described in
694 @rinternals{Contexts}
697 Internals Reference @expansion{} Translation @expansion{} Context.
699 lists the engravers used for that context.
702 It can be useful to shuffle around these plug-ins. This is done by
703 starting a new context with @code{\new} or @code{\context}, and
709 \new @var{context} \with @{
717 @emph{@dots{}music@dots{}}
722 where the @dots{} should be the name of an engraver. Here is a simple
723 example which removes @code{Time_signature_engraver} and
724 @code{Clef_engraver} from a @code{Staff} context,
726 @lilypond[quote,verbatim]
728 \new Staff \relative {
732 \remove "Time_signature_engraver"
733 \remove "Clef_engraver"
740 In the second staff there are no time signature or clef symbols. This
741 is a rather crude method of making objects disappear since it will affect
742 the entire staff. This method also influences the spacing, which may or
743 may not be desirable. More sophisticated methods of blanking objects
744 are shown in @rlearning{Visibility and color of objects}.
746 The next example shows a practical application. Bar lines and time
747 signatures are normally synchronized across the score. This is done
748 by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
749 This plug-in keeps an administration of time signature, location
750 within the measure, etc. By moving these engraver from @code{Score} to
751 @code{Staff} context, we can have a score where each staff has its own
754 @cindex polymetric scores
755 @cindex time signature, multiple
757 @lilypond[quote,verbatim]
761 \consists "Timing_translator"
762 \consists "Default_bar_line_engraver"
769 \consists "Timing_translator"
770 \consists "Default_bar_line_engraver"
780 \remove "Timing_translator"
781 \remove "Default_bar_line_engraver"
789 The order in which the engravers are specified is the order in
790 which they are called to carry out their processing. Usually the
791 order in which the engravers are specified does not matter, but in
792 a few special cases the order is important, for example where one
793 engraver writes a property and another reads it, or where one
794 engraver creates a grob and another must process it.
796 The following orderings are important:
800 the @code{Bar_engraver} must normally be first,
803 the @code{New_fingering_engraver} must come before the
804 @code{Script_column_engraver},
807 the @code{Timing_translator} must come before the
808 @code{Bar_number_engraver}.
814 @file{ly/engraver-init.ly}.
817 @node Changing context default settings
818 @subsection Changing context default settings
820 @cindex default context properties, changing
821 @cindex context properties, changing defaults
823 Context and grob properties can be changed with @code{\set}
824 and @code{\override} commands, as described in
825 @ref{Modifying properties}. These commands create music events,
826 making the changes take effect at the point in time the music
829 In contrast, this section explains how to change the @emph{default}
830 values of context and grob properties at the time the context is
831 created. There are two ways of doing this. One modifies the default
832 values in all contexts of a particular type, the other modifies the
833 default values in just one particular instance of a context.
836 * Changing all contexts of the same type::
837 * Changing just one specific context::
838 * Order of precedence::
841 @node Changing all contexts of the same type
842 @unnumberedsubsubsec Changing all contexts of the same type
844 @cindex \context in \layout block
848 The default context settings which are to be used for typesetting in
849 @code{Score}, @code{Staff}, @code{Voice} and other contexts may be
850 specified in a @code{\context} block within any @code{\layout}
853 Settings for Midi output as opposed to typesetting will have to be
854 separately specified in @code{\midi} blocks (see @ref{Output
855 definitions - blueprints for contexts}).
857 The @code{\layout} block should be placed within the @code{\score}
858 block to which it is to apply, after the music.
864 [context settings for all Voice contexts]
868 [context settings for all Staff contexts]
873 The following types of settings may be specified:
877 An @code{\override} command, but with the context name omitted
879 @lilypond[quote,verbatim]
882 a'4^"Thicker stems" a a a
888 \override Stem.thickness = #4.0
895 Directly setting a context property
897 @lilypond[quote,verbatim]
900 a'4^"Smaller font" a a a
913 A predefined command such as @code{\dynamicUp} or a music
914 expression like @code{\accidentalStyle dodecaphonic}
916 @lilypond[quote,verbatim]
919 a'4^"Dynamics above" a a a
929 \accidentalStyle dodecaphonic
936 A user-defined variable containing a @code{\with} block; for details
937 of the @code{\with} block see
938 @ref{Changing just one specific context}.
940 @lilypond[quote,verbatim]
941 StaffDefaults = \with {
948 a'4^"Smaller font" a a a
963 Property-setting commands can be placed in a @code{\layout} block
964 without being enclosed in a @code{\context} block. Such settings
965 are equivalent to including the same property-setting commands at
966 the start of every context of the type specified. If no context
967 is specified @emph{every} bottom-level context is affected, see
968 @ref{Bottom-level contexts - voices}. The syntax of a
969 property-setting command in a @code{\layout} block is the same as
970 the same command written in the music stream.
972 @lilypond[quote,verbatim]
976 a'4^"Smaller font" a a a
981 \accidentalStyle dodecaphonic
983 \override Voice.Stem.thickness = #4.0
989 @node Changing just one specific context
990 @unnumberedsubsubsec Changing just one specific context
995 The context properties of just one specific context instance can be
996 changed in a @code{\with} block. All other context instances of the
997 same type retain the default settings built into LilyPond and modified
998 by any @code{\layout} block within scope. The @code{\with} block
999 must be placed immediately after the @code{\new} @var{context-type}
1003 \new Staff \with @{ [context settings for this context instance only] @}
1009 Since such a @q{context modification} is specified inside of
1010 music, it will affect @emph{all} outputs (typesetting @emph{and}
1011 Midi) as opposed to changes within an output definition.
1013 The following types of settings may be specified:
1017 An @code{\override} command, but with the context name omitted
1019 @lilypond[quote,verbatim]
1022 \new Voice \with { \override Stem.thickness = #4.0 }
1025 a'4^"Thick stems" a a a
1034 Directly setting a context property
1036 @lilypond[quote,verbatim]
1041 a'4^"Default font" a a a
1045 \new Staff \with { fontSize = #-4 }
1048 a'4^"Smaller font" a a a
1057 A predefined command such as @code{\dynamicUp}
1059 @lilypond[quote,verbatim]
1065 a'4^"Dynamics below" a a a
1070 \new Staff \with { \accidentalStyle dodecaphonic }
1072 \new Voice \with { \dynamicUp }
1075 a'4^"Dynamics above" a a a
1086 @node Order of precedence
1087 @unnumberedsubsubsec Order of precedence
1089 The value of a property which applies at a particular time is
1090 determined as follows:
1094 if an @code{\override} or @code{\set} command in the input stream is
1095 in effect that value is used,
1098 otherwise the default value taken from a @code{\with} statement
1099 on the context initiation statement is used,
1102 otherwise the default value taken from the most recent appropriate
1103 @code{\context} block in the @code{\layout} or @code{\midi} blocks
1107 otherwise the LilyPond built-in default is used.
1112 @rlearning{Modifying context properties}.
1115 @ref{Contexts explained},
1116 @ref{Bottom-level contexts - voices},
1117 @ref{The set command},
1118 @ref{The override command},
1119 @ref{The layout block,,The @code{@bs{}layout} block}.
1122 @node Defining new contexts
1123 @subsection Defining new contexts
1125 @cindex contexts, defining new
1126 @cindex engravers, including in contexts
1141 Specific contexts, like @code{Staff} and @code{Voice}, are made from
1142 simple building blocks. It is possible to create new types of
1143 contexts with different combinations of engraver plug-ins.
1145 The next example shows how to build a different type of
1146 @code{Voice} context from scratch. It will be similar to
1147 @code{Voice}, but only prints centered slash note heads. It can be used
1148 to indicate improvisation in jazz pieces,
1150 @lilypond[quote,ragged-right]
1151 \layout { \context {
1153 \type "Engraver_group"
1154 \consists "Note_heads_engraver"
1155 \consists "Rhythmic_column_engraver"
1156 \consists "Text_engraver"
1157 \consists "Pitch_squash_engraver"
1158 squashedPosition = #0
1159 \override NoteHead.style = #'slash
1164 \accepts "ImproVoice"
1168 a'4 d8 bes8 \new ImproVoice { c4^"ad lib" c
1169 c4 c^"undress" c_"while playing :)" c }
1175 These settings are defined within a @code{\context} block inside a
1176 @code{\layout} block,
1186 In the following discussion, the example input shown should go in place
1187 of the @dots{} in the previous fragment.
1189 First it is necessary to define a name for the new context:
1195 Since it is similar to the @code{Voice} context, we want commands that
1196 work in (existing) @code{Voice} contexts to continue working. This is
1197 achieved by giving the new context an alias of @code{Voice},
1203 The context will print notes and instructive texts, so we need to add
1204 the engravers which provide this functionality, plus the engraver which
1205 groups notes, stems and rests which occur at the same musical moment
1209 \consists "Note_heads_engraver"
1210 \consists "Text_engraver"
1211 \consists "Rhythmic_column_engraver"
1214 The note heads should all be placed on the center line,
1217 \consists "Pitch_squash_engraver"
1218 squashedPosition = #0
1221 The @code{Pitch_squash_engraver} modifies note heads (created
1222 by the @code{Note_heads_engraver}) and sets their vertical
1223 position to the value of @code{squashedPosition}, in this
1224 case@tie{}@code{0}, the center line.
1226 The notes look like a slash, and have no stem,
1229 \override NoteHead.style = #'slash
1233 All these plug-ins have to communicate under the control of the
1234 context. The mechanisms with which contexts communicate are
1235 established by declaring the context @code{\type}. Within a
1236 @code{\layout} block, most contexts will be of type
1237 @code{Engraver_group}. Some special contexts and contexts in
1238 @code{\midi} blocks use other context types. Copying and
1239 modifying an existing context definition will also fill in the
1240 type. Since this example creates a definition from scratch, it
1241 needs to be specified explicitly.
1244 \type "Engraver_group"
1247 Put together, we get
1252 \type "Engraver_group"
1253 \consists "Note_heads_engraver"
1254 \consists "Text_engraver"
1255 \consists "Rhythmic_column_engraver"
1256 \consists "Pitch_squash_engraver"
1257 squashedPosition = #0
1258 \override NoteHead.style = #'slash
1265 Contexts form hierarchies. We want to place the @code{ImproVoice}
1266 context within the @code{Staff} context, just like normal @code{Voice}
1267 contexts. Therefore, we modify the @code{Staff} definition with the
1268 @code{\accepts} command,
1278 The opposite of @code{\accepts} is @code{\denies},
1279 which is sometimes needed when reusing existing context definitions.
1281 Putting both into a @code{\layout} block, like
1291 \accepts "ImproVoice"
1296 Then the output at the start of this subsection can be entered as
1304 c c_"while playing :)"
1310 To complete this example, changes affecting the context hierarchy
1311 should be repeated in a @code{\midi} block so that Midi output
1312 depends on the same context relations.
1316 Internals Reference:
1317 @rinternals{Note_heads_engraver},
1318 @rinternals{Text_engraver},
1319 @rinternals{Rhythmic_column_engraver},
1320 @rinternals{Pitch_squash_engraver}.
1323 @node Context layout order
1324 @subsection Context layout order
1326 @cindex contexts, layout order
1330 Contexts are normally positioned in a system from top to bottom
1331 in the order in which they are encountered in the input file. When
1332 contexts are nested, the outer context will include inner nested
1333 contexts as specified in the input file, provided the inner contexts
1334 are included in the outer context's @qq{accepts} list. Nested
1335 contexts which are not included in the outer context's @qq{accepts}
1336 list will be repositioned below the outer context rather than nested
1339 The @qq{accepts} list of a context can be changed with the
1340 @code{\accepts} or @code{\denies} commands. @code{\accepts} adds a
1341 context to the @qq{accepts} list and @code{\denies} removes a context
1344 For example, a square-braced staff group is not usually found within a
1345 curved-braced staff with connecting staff bars, and a @code{GrandStaff}
1346 does not accept a @code{StaffGroup} inside it by default.
1348 @lilypond[verbatim,quote]
1355 \new Staff { \set Staff.instrumentName = bottom f'1 }
1360 However, by using the @code{\accepts} command, @code{StaffGroup} can be
1361 added to the @code{GrandStaff} context:
1363 @lilypond[verbatim,quote]
1370 \new Staff { \set Staff.instrumentName = bottom f'1 }
1375 \accepts "StaffGroup"
1381 @code{\denies} is mainly used when a new context is being based on
1382 another, but the required nesting differs. For example, the
1383 @code{VaticanaStaff} context is based on the @code{Staff} context, but
1384 with the @code{VaticanaVoice} context substituted for the @code{Voice}
1385 context in the @qq{accepts} list.
1387 @cindex contexts, implicit
1388 @cindex implicit contexts
1389 @funindex \defaultchild
1391 Note that a context will be silently created implicitly if a
1392 command is encountered when there is no suitable context available
1395 Within a context definition, the type of subcontext to be
1396 implicitly created is specified using @code{\defaultchild}. A
1397 number of music events require a @samp{Bottom} context: when such
1398 an event is encountered, subcontexts are created recursively until
1399 reaching a context with no @samp{defaultchild} setting.
1401 Implicit context creation can at times give rise to unexpected new
1402 staves or scores. Using @code{\new} to create contexts explicitly
1403 avoids those problems.
1405 @cindex alignAboveContext
1406 @cindex alignBelowContext
1407 @funindex alignAboveContext
1408 @funindex alignBelowContext
1410 Sometimes a context is required to exist for just a brief period, a
1411 good example being the staff context for an ossia. This is usually
1412 achieved by introducing the context definition at the appropriate
1413 place in parallel with corresponding section of the main music.
1414 By default, the temporary context will be placed below all the
1415 existing contexts. To reposition it above the context called
1416 @qq{main}, it should be defined like this:
1419 @code{\new Staff \with @{ alignAboveContext = #"main" @} }
1422 A similar situation arises when positioning a temporary lyrics
1423 context within a multi-staved layout such as a @code{ChoirStaff},
1424 for example, when adding a second verse to a repeated section.
1425 By default the temporary lyrics context will be placed beneath the
1426 lower staves. By defining the temporary lyrics context with
1427 @code{alignBelowContext} it can be positioned correctly beneath
1428 the (named) lyrics context containing the first verse.
1430 Examples showing this repositioning of temporary contexts can be
1431 found elsewhere --- see @rlearning{Nesting music expressions},
1432 @ref{Modifying single staves} and @ref{Techniques specific to lyrics}.
1436 @rlearning{Nesting music expressions}.
1439 @ref{Modifying single staves},
1440 @ref{Techniques specific to lyrics}.
1443 @rprogram{An extra staff appears}.
1446 @file{ly/engraver-init.ly}.
1449 @node Explaining the Internals Reference
1450 @section Explaining the Internals Reference
1453 * Navigating the program reference::
1454 * Layout interfaces::
1455 * Determining the grob property::
1456 * Naming conventions::
1459 @node Navigating the program reference
1460 @subsection Navigating the program reference
1462 @c TODO remove this (it's in the LM)
1463 @c Replace with more factual directions
1465 Suppose we want to move the fingering indication in the fragment
1468 @lilypond[quote,fragment,verbatim]
1472 If you visit the documentation on fingering instructions (in
1473 @ref{Fingering instructions}), you will notice:
1478 Internals Reference: @rinternals{Fingering}.
1483 @c outdated info; probably will delete.
1485 This fragment points to two parts of the program reference: a page
1486 on @code{FingeringEvent} and one on @code{Fingering}.
1488 The page on @code{FingeringEvent} describes the properties of the music
1489 expression for the input @w{@code{-2}}. The page contains many links
1490 forward. For example, it says
1493 Accepted by: @rinternals{Fingering_engraver},
1497 That link brings us to the documentation for the Engraver, the
1501 This engraver creates the following layout objects: @rinternals{Fingering}.
1504 In other words, once the @code{FingeringEvent}s are interpreted, the
1505 @code{Fingering_engraver} plug-in will process them.
1509 @c I can't figure out what this is supposed to mean. -gp
1511 The @code{Fingering_engraver} is also listed to create
1512 @rinternals{Fingering} objects,
1514 @c old info? it doesn't make any sense to me with our current docs.
1516 second bit of information listed under @b{See also} in the Notation
1521 The programmer's reference is available as an HTML document. It is
1522 highly recommended that you read it in HTML form, either online or
1523 by downloading the HTML documentation. This section will be much more
1524 difficult to understand if you are using the
1528 Follow the link to @rinternals{Fingering}. At the top of the
1532 Fingering objects are created by: @rinternals{Fingering_engraver} and
1533 @rinternals{New_fingering_engraver}.
1536 By following related links inside the program reference, we can follow the
1537 flow of information within the program:
1541 @item @rinternals{Fingering}:
1542 @rinternals{Fingering} objects are created by:
1543 @rinternals{Fingering_engraver}
1545 @item @rinternals{Fingering_engraver}:
1546 Music types accepted: @rinternals{fingering-event}
1548 @item @rinternals{fingering-event}:
1549 Music event type @code{fingering-event} is in Music expressions named
1550 @rinternals{FingeringEvent}
1553 This path goes against the flow of information in the program: it
1554 starts from the output, and ends at the input event. You could
1555 also start at an input event, and read with the flow of
1556 information, eventually ending up at the output object(s).
1558 The program reference can also be browsed like a normal document. It
1559 contains chapters on
1561 @rinternals{Music definitions},
1564 @code{Music definitions}
1566 on @rinternals{Translation}, and the @rinternals{Backend}. Every
1567 chapter lists all the definitions used and all properties that may be
1571 @node Layout interfaces
1572 @subsection Layout interfaces
1574 @cindex interface, layout
1575 @cindex layout interface
1578 The HTML page that we found in the previous section describes the
1579 layout object called @rinternals{Fingering}. Such an object is a
1580 symbol within the score. It has properties that store numbers (like
1581 thicknesses and directions), but also pointers to related objects. A
1582 layout object is also called a @emph{Grob}, which is short for Graphical
1583 Object. For more details about Grobs, see @rinternals{grob-interface}.
1585 The page for @code{Fingering} lists the definitions for the
1586 @code{Fingering} object. For example, the page says
1589 @code{padding} (dimension, in staff space):
1595 which means that the number will be kept at a distance of at least 0.5
1599 Each layout object may have several functions as a notational or
1600 typographical element. For example, the Fingering object
1601 has the following aspects
1605 Its size is independent of the horizontal spacing, unlike slurs or beams.
1608 It is a piece of text. Granted, it is usually a very short text.
1611 That piece of text is typeset with a font, unlike slurs or beams.
1614 Horizontally, the center of the symbol should be aligned to the
1615 center of the note head.
1618 Vertically, the symbol is placed next to the note and the staff.
1621 The vertical position is also coordinated with other superscript
1622 and subscript symbols.
1625 Each of these aspects is captured in so-called @emph{interface}s,
1626 which are listed on the @rinternals{Fingering} page at the bottom
1629 This object supports the following interfaces:
1630 @rinternals{item-interface},
1631 @rinternals{self-alignment-interface},
1632 @rinternals{side-position-interface}, @rinternals{text-interface},
1633 @rinternals{text-script-interface}, @rinternals{font-interface},
1634 @rinternals{finger-interface}, and @rinternals{grob-interface}.
1637 Clicking any of the links will take you to the page of the respective
1638 object interface. Each interface has a number of properties. Some of
1639 them are not user-serviceable (@q{Internal properties}), but others
1642 We have been talking of @emph{the} @code{Fingering} object, but actually it
1643 does not amount to much. The initialization file (see
1644 @rlearning{Other sources of information})
1645 @file{scm/define-grobs.scm} shows the soul of the @q{object},
1650 (avoid-slur . around)
1651 (slur-padding . 0.2)
1652 (staff-padding . 0.5)
1653 (self-alignment-X . 0)
1654 (self-alignment-Y . 0)
1655 (script-priority . 100)
1656 (stencil . ,ly:text-interface::print)
1657 (direction . ,ly:script-interface::calc-direction)
1658 (font-encoding . fetaText)
1659 (font-size . -5) ; don't overlap when next to heads.
1660 (meta . ((class . Item)
1661 (interfaces . (finger-interface
1663 text-script-interface
1665 side-position-interface
1666 self-alignment-interface
1667 item-interface))))))
1671 As you can see, the @code{Fingering} object is nothing more than a
1672 bunch of variable settings, and the webpage in the Internals Reference
1673 is directly generated from this definition.
1676 @node Determining the grob property
1677 @subsection Determining the grob property
1679 @c TODO remove this (it's in the LM)
1680 @c Replace with more factual directions
1682 Recall that we wanted to change the position of the @b{2} in
1684 @lilypond[quote,fragment,verbatim]
1688 Since the @b{2} is vertically positioned next to its note, we have to
1689 meddle with the interface associated with this positioning. This is
1690 done using @code{side-position-interface}. The page for this interface
1694 @code{side-position-interface}
1696 Position a victim object (this one) next to other objects (the
1697 support). The property @code{direction} signifies where to put the
1698 victim object relative to the support (left or right, up or down?)
1703 Below this description, the variable @code{padding} is described as
1708 (dimension, in staff space)
1710 Add this much extra space between objects that are next to each other.
1714 By increasing the value of @code{padding}, we can move the
1715 fingering away from the note head. The following command inserts
1716 3 staff spaces of white
1717 between the note and the fingering:
1719 \once \override Voice.Fingering.padding = #3
1722 Inserting this command before the Fingering object is created,
1723 i.e., before @code{c2}, yields the following result:
1725 @lilypond[quote,fragment,verbatim]
1726 \once \override Voice.Fingering.padding = #3
1731 In this case, the context for this tweak is @code{Voice}. This
1732 fact can also be deduced from the program reference, for the page for
1733 the @rinternals{Fingering_engraver} plug-in says
1736 Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
1740 @node Naming conventions
1741 @subsection Naming conventions
1743 Another thing that is needed, is an overview of the various naming
1747 @item scheme functions: lowercase-with-hyphens (incl. one-word
1749 @item scheme functions: ly:plus-scheme-style
1750 @item music events, music classes and music properties:
1752 @item Grob interfaces: scheme-style
1753 @item backend properties: scheme-style (but X and Y!)
1754 @item contexts (and MusicExpressions and grobs): Capitalized or
1756 @item context properties: lowercaseFollowedByCamelCase
1758 Capitalized_followed_by_lowercase_and_with_underscores
1761 Questions to be answered:
1763 @item Which of these are conventions and which are rules?
1764 @item Which are rules of the underlying language, and which are
1768 @node Modifying properties
1769 @section Modifying properties
1771 @c TODO change the menu and subsection node names to use
1772 @c backslash once the new macro to handle the refs
1773 @c is available. Need to find and change all refs at
1774 @c the same time. -td
1777 * Overview of modifying properties::
1779 * The override command::
1780 * The tweak command::
1781 * set versus override::
1782 * Modifying alists::
1786 @node Overview of modifying properties
1787 @subsection Overview of modifying properties
1789 Each context is responsible for creating certain types of graphical
1790 objects. The settings used for printing these objects are also stored by
1791 context. By changing these settings, the appearance of objects can be
1794 There are two different kinds of properties stored in contexts:
1795 context properties and grob properties. Context properties are
1796 properties that apply to the context as a whole and control
1797 how the context itself is displayed. In contrast, grob properties
1798 apply to specific grob types that will be displayed in the context.
1800 The @code{\set} and @code{\unset} commands are used to change values
1801 for context properties. The @code{\override} and @code{\revert}
1802 commands are used to change values for grob properties.
1805 The syntax for this is
1808 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1811 Here @var{name} is the name of a graphical object, like
1812 @code{Stem} or @code{NoteHead}, and @var{property} is an internal
1813 variable of the formatting system (@q{grob property} or @q{layout
1814 property}). The latter is a symbol, so it must be quoted. The
1815 subsection @ref{Modifying properties}, explains what to fill in
1816 for @var{name}, @var{property}, and @var{value}. Here we only
1817 discuss the functionality of this command.
1822 \override Staff.Stem.thickness = #4.0
1826 makes stems thicker (the default is 1.3, with staff line thickness as a
1827 unit). Since the command specifies @code{Staff} as context, it only
1828 applies to the current staff. Other staves will keep their normal
1829 appearance. Here we see the command in action:
1831 @lilypond[quote,fragment,verbatim]
1833 \override Staff.Stem.thickness = #4.0
1839 The @code{\override} command changes the definition of the @code{Stem}
1840 within the current @code{Staff}. After the command is interpreted
1841 all stems are thickened.
1843 Analogous to @code{\set}, the @var{context} argument may be left out,
1844 causing the default context @code{Voice} to be used. Adding
1845 @code{\once} applies the change during one timestep only.
1847 @lilypond[quote,fragment,verbatim]
1849 \once \override Stem.thickness = #4.0
1854 The @code{\override} must be done before the object is
1855 started. Therefore, when altering @emph{Spanner} objects such as slurs
1856 or beams, the @code{\override} command must be executed at the moment
1857 when the object is created. In this example,
1859 @lilypond[quote,fragment,verbatim]
1860 \override Slur.thickness = #3.0
1862 \override Beam.beam-thickness = #0.6
1867 the slur is fatter but the beam is not. This is because the command for
1868 @code{Beam} comes after the Beam is started, so it has no effect.
1870 Analogous to @code{\unset}, the @code{\revert} command for a context
1871 undoes an @code{\override} command; like with @code{\unset}, it only
1872 affects settings that were made in the same context. In other words, the
1873 @code{\revert} in the next example does not do anything.
1876 \override Voice.Stem.thickness = #4.0
1877 \revert Staff.Stem.thickness
1880 Some tweakable options are called @q{subproperties} and reside inside
1881 properties. To tweak those, use commands of the form
1883 @c leave this as a long long
1885 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
1892 \override Stem.details.beamed-lengths = #'(4 4 3)
1898 Internals Reference:
1899 @rinternals{Backend},
1900 @rinternals{All layout objects},
1901 @rinternals{OverrideProperty},
1902 @rinternals{RevertProperty},
1903 @rinternals{PropertySet}.
1906 The back-end is not very strict in type-checking object properties.
1907 Cyclic references in Scheme values for properties can cause hangs
1908 or crashes, or both.
1911 @node The set command
1912 @subsection The @code{@bs{}set} command
1916 @cindex changing properties
1918 Each context has a set of @emph{properties}, variables contained
1919 in that context. Context properties are changed with the @code{\set}
1920 command, which has the following syntax:
1923 \set @var{context}.@var{property} = #@var{value}
1926 @var{value} is a Scheme object, which is why it must be preceded by
1927 the @code{#}@tie{}character.
1929 Contexts properties are usually named in
1930 @code{studlyCaps}. They mostly control the translation from
1931 music to notation, e.g. @code{localAlterations} (for determining
1932 whether to print accidentals), or @code{measurePosition} (for
1933 determining when to print a bar line). Context properties can
1934 change value over time while interpreting a piece of music;
1935 @code{measurePosition} is an obvious example of
1936 this. Context properties are modified with @code{\set}.
1938 For example, multimeasure rests will be combined into a single bar
1939 if the context property @code{skipBars} is set to @code{#t}:
1941 @lilypond[quote,fragment,verbatim]
1943 \set Score.skipBars = ##t
1947 If the @var{context} argument is left out, then the property will be
1948 set in the current bottom context (typically @code{ChordNames},
1949 @code{Voice}, @code{TabVoice}, or @code{Lyrics}).
1951 @lilypond[quote,fragment,verbatim]
1952 \set Score.autoBeaming = ##f
1955 \set autoBeaming = ##t
1963 The change is applied @q{on-the-fly}, during the music, so that the
1964 setting only affects the second group of eighth notes.
1966 Note that the bottom-most context does not always contain the property
1967 that you wish to change -- for example, attempting to set the
1968 @code{skipBars} property of the default bottom context, in this case
1969 @code{Voice}, will have no effect, because skipBars is a property of
1970 the @code{Score} context.
1972 @lilypond[quote,fragment,verbatim]
1978 Contexts are hierarchical, so if an enclosing context was specified, for
1979 example @code{Staff}, then the change would also apply to all
1980 @code{Voice}s in the current staff.
1984 The @code{\unset} command:
1987 \unset @var{context}.@var{property}
1991 is used to remove the definition of @var{property} from
1992 @var{context}. This command removes
1993 the definition only if it is set in @var{context}.
1994 Properties that have been set in enclosing contexts will
1995 not be altered by an unset in an enclosed context:
1997 @lilypond[quote,fragment,verbatim]
1998 \set Score.autoBeaming = ##t
2002 \unset Score.autoBeaming
2010 Like @code{\set}, the @var{context} argument does not have to be
2011 specified for a bottom context, so the two statements
2014 \set Voice.autoBeaming = ##t
2015 \set autoBeaming = ##t
2019 are equivalent if the current bottom context is @code{Voice}.
2023 Preceding a @code{\set} command by @code{\once} makes the
2024 setting apply to only a single time-step:
2026 @lilypond[quote,fragment,verbatim]
2028 \once \set fontSize = #4.7
2033 A full description of all available context properties is in the
2034 internals reference, see
2036 @rinternals{Tunable context properties}.
2039 Translation @expansion{} Tunable context properties.
2043 Internals Reference:
2044 @rinternals{Tunable context properties}.
2047 @node The override command
2048 @subsection The @code{\override} command
2050 @cindex grob properties
2051 @cindex properties, grob
2054 There is a special type of context property: the grob
2055 description. Grob descriptions are named in @code{StudlyCaps}
2056 (starting with capital letters). They contain the
2057 @q{default settings} for a particular kind of grob as an
2058 association list. See @file{scm/define-grobs.scm}
2059 to see the settings for each grob description. Grob descriptions
2060 are modified with @code{\override}.
2062 The syntax for the @code{\override} command is
2065 \override [@var{context}.]@var{GrobName}.@var{property} = #@var{value}
2068 For example, we can increase the thickness of a note stem by
2069 overriding the @code{thickness} property of the @code{Stem}
2072 @lilypond[quote,fragment,verbatim]
2074 \override Voice.Stem.thickness = #3.0
2078 If no context is specified in an @code{\override}, the bottom
2081 @lilypond[quote,fragment,verbatim]
2082 \override Staff.Stem.thickness = #3.0
2086 \override Stem.thickness = #0.5
2095 Some tweakable options are called @q{subproperties} and reside inside
2096 properties. To tweak those, use commands in the form
2099 \override Stem.details.beamed-lengths = #'(4 4 3)
2102 or to modify the ends of spanners, use a form like these
2105 \override TextSpanner.bound-details.left.text = #"left text"
2106 \override TextSpanner.bound-details.right.text = #"right text"
2110 @cindex reverting overrides
2111 @cindex overrides, reverting
2113 The effects of @code{\override} can be undone by @code{\revert}.
2115 The syntax for the @code{\revert} command is
2118 \revert [@var{context}.]@var{GrobName}.@var{property}
2123 @lilypond[quote,verbatim]
2126 \override Voice.Stem.thickness = #3.0
2128 \revert Voice.Stem.thickness
2133 The effects of @code{\override} and @code{\revert} apply to all
2134 grobs in the affected context from the current time forward:
2136 @lilypond[quote,verbatim]
2140 \override Staff.Stem.thickness = #3.0
2145 \revert Staff.Stem.thickness
2152 @cindex overriding for only one moment
2154 @code{\once} can be used with @code{\override}
2155 to affect only the current time step:
2157 @lilypond[quote,verbatim]
2160 \override Stem.thickness = #3.0
2165 \once \override Stem.thickness = #3.0
2173 Commands which change output generally look like
2176 \override Voice.Stem.thickness = #3.0
2180 To construct this tweak we must determine these bits of information:
2183 @item the context: here @code{Voice}.
2184 @item the layout object: here @code{Stem}.
2185 @item the layout property: here @code{thickness}.
2186 @item a sensible value: here @code{3.0}.
2189 @cindex internal documentation
2190 @cindex finding graphical objects
2191 @cindex graphical object descriptions
2194 @cindex internal documentation
2196 For many properties, regardless of the data type of the property, setting the
2197 property to false (@code{#f}) will result in turning it off, causing
2198 LilyPond to ignore that property entirely. This is particularly useful for
2199 turning off grob properties which may otherwise be causing problems.
2201 We demonstrate how to glean this information from the notation manual
2202 and the program reference.
2206 Internals Reference:
2207 @rinternals{Backend}
2210 @node The tweak command
2211 @subsection The @code{\tweak} command
2216 Changing grob properties
2217 with @code{\override} causes the changes to apply to all of the
2218 given grobs in the context at the moment the change applies.
2219 Sometimes, however, it is desirable to have changes apply to just
2220 one grob, rather than to all grobs in the affected context. This is
2221 accomplished with the @code{\tweak} command, which has the following
2225 \tweak [@var{layout-object}.]@var{grob-property} @var{value}
2228 Specifying @var{layout-object} is optional.
2229 The @code{\tweak} command applies to the music object that immediately
2230 follows @var{value} in the music stream.
2233 In some cases, it is possible to take a short-cut for tuning
2234 graphical objects. For objects that are created directly from
2235 an item in the input file, you can use the @code{\tweak} command.
2238 @lilypond[verbatim,quote]
2244 \tweak duration-log #1
2254 The main use of the @code{\tweak} command is to modify just
2255 one of a number of notation elements which start at the same musical
2256 moment, like the notes of a chord, or tuplet brackets which start
2259 The @code{\tweak} command sets a property in the following object
2260 directly, without requiring the grob name or context to be
2261 specified. For this to work, it is necessary for the @code{\tweak}
2262 command to remain immediately adjacent to the object to which it is
2263 to apply after the input file has been converted to a music stream.
2264 This is often not the case, as many additional elements are inserted
2265 into the music stream implicitly. For example, when a note which is
2266 not part of a chord is processed, LilyPond implicitly inserts a
2267 @code{ChordEvent} event before the note, so separating the tweak
2268 from the note. However, if chord symbols are placed round the
2269 tweak and the note, the @code{\tweak} command comes after the
2270 @code{ChordEvent} in the music stream, so remaining adjacent to the
2271 note, and able to modify it.
2275 @lilypond[verbatim,fragment,quote]
2276 <\tweak color #red c''>4
2282 @lilypond[verbatim,fragment,quote]
2283 \tweak color #red c''4
2288 For an introduction to the syntax and uses of the tweak command
2289 see @rlearning{Tweaking methods}.
2291 When several similar items are placed at the same musical moment,
2292 the @code{\override} command cannot be used to modify just one of
2293 them -- this is where the @code{\tweak} command must be used.
2294 Items which may appear more than once at the same musical moment
2295 include the following:
2297 @c TODO expand to include any further uses of \tweak
2299 @item note heads of notes inside a chord
2300 @item articulation signs on a single note
2301 @item ties between notes in a chord
2302 @item tuplet brackets starting at the same time
2305 @c TODO add examples of these
2307 @cindex chord, modifying one note in
2309 In this example, the color of one note head and the type of another
2310 note head are modified within a single chord:
2312 @lilypond[verbatim,fragment,quote]
2317 \tweak duration-log #1
2322 @code{\tweak} can be used to modify slurs:
2324 @lilypond[verbatim,quote]
2325 \relative { c'-\tweak thickness #5 ( d e f) }
2329 For the @code{\tweak} command to work, it must
2330 remain immediately adjacent to the object to which it is
2331 to apply after the input file has been converted to a music stream.
2332 Tweaking a whole chord does not do anything since its music event
2333 only acts as a container, and all layout objects are created from events
2334 inside of the @code{EventChord}:
2336 @lilypond[verbatim,fragment,quote]
2337 \tweak color #red c''4
2338 \tweak color #red <c'' e''>4
2339 <\tweak color #red c'' e''>4
2342 The simple @code{\tweak} command cannot be used to modify any object
2343 that is not directly created from the input. In particular
2344 it will not affect stems, automatic
2345 beams or accidentals, since these are generated later by
2346 @code{NoteHead} layout objects rather than by music elements in the
2349 Such indirectly created layout objects can be tweaked using the form
2350 of the @code{\tweak} command in which the grob name is specified
2353 @lilypond[fragment,verbatim,quote]
2354 \tweak Stem.color #red
2355 \tweak Beam.color #green c''8 e''
2356 <c'' e'' \tweak Accidental.font-size #-3 ges''>4
2359 @code{\tweak} cannot be used to modify clefs or time
2360 signatures, since these become separated from any preceding
2361 @code{\tweak} command in the input stream by the automatic
2362 insertion of extra elements required to specify the context.
2364 Several @code{\tweak} commands may be placed before a
2365 notational element -- all affect it:
2367 @lilypond[verbatim,fragment,quote]
2369 -\tweak style #'dashed-line
2370 -\tweak dash-fraction #0.2
2371 -\tweak thickness #3
2377 The music stream which is generated from a section of an input file,
2378 including any automatically inserted elements, may be examined,
2379 see @rextend{Displaying music expressions}. This may be helpful in
2380 determining what may be modified by a @code{\tweak} command, or
2381 in determining how to adjust the input to make a @code{\tweak}
2386 @rlearning{Tweaking methods}.
2389 @rextend{Displaying music expressions}.
2393 @cindex tweaking control points
2394 @cindex control points, tweaking
2396 The @code{\tweak} command cannot be used to modify the control
2397 points of just one of several ties in a chord, other than the first
2398 one encountered in the input file.
2400 @node set versus override
2401 @subsection @code{\set} vs. @code{\override}
2403 @c TODO Should't a bunch of that be explained earlier?
2407 Both @code{\set} and @code{\override} manipulate properties
2408 associated with contexts. In either case, properties heed the
2409 hierarchy of contexts: properties not set in a context itself show
2410 the values of the respective parent context.
2412 Values and lifetime of context properties are dynamic and only
2413 available when music is being interpreted, @q{iterated}. At the
2414 time of context creation, properties are initialized from the
2415 corresponding context definition and possible context
2416 modifications. Afterwards, changes are achieved with
2417 property-setting commands in the music itself.
2419 Now grob definitions are a special category of context properties.
2420 Since their structure, bookkeeping and use is different from
2421 ordinary context properties, they are accessed with a different
2422 set of commands, and treated separately in the documentation.
2424 As opposed to plain context properties, grob definitions are
2425 subdivided into grob properties. A @qq{grob} (graphical object)
2426 is usually created by an engraver at the time of interpreting a
2427 music expression and receives its initial properties from the
2428 current grob definition of the engraver's context. The engraver
2429 (or other @q{backend} parts of LilyPond) may subsequently add or
2430 change properties to the grob, but that does not affect the
2431 context's grob definition.
2433 What we call @q{grob properties} in the context of user-level
2434 tweaking are actually the properties of a context's grob
2435 definition. In contrast to ordinary context properties, grob
2436 definitions have the bookkeeping required to keep track of its
2437 parts, the individual grob properties (and even subproperties of
2438 them) separately so that it is possible to define those parts in
2439 different contexts and have the overall grob definition at the
2440 time of grob creation be assembled from pieces provided in
2441 different contexts among the current context and its parents.
2443 Grob definitions are manipulated using @code{\override} and
2444 @code{\revert} and have a name starting with a capital letter
2445 (like @samp{NoteHead}) whereas ordinary context properties are
2446 manipulated using @code{\set} and @code{\unset} and are named
2447 starting with a lowercase letter.
2449 @cindex tweak, relation to @code{\override}
2451 @funindex \overrideProperty
2452 The special commands @code{\tweak} and @code{\overrideProperty}
2453 change grob properties bypassing context properties completely.
2454 Instead they catch grobs as they are being created and then
2455 directly set properties on them when they originate from a tweaked
2456 music event or are of a particular kind, respectively.
2458 @node Modifying alists
2459 @subsection Modifying alists
2461 Some user-configurable properties are internally represented as
2462 @emph{alists} (association lists), which store pairs of
2463 @emph{keys} and @emph{values}. The structure of an alist is:
2466 '((@var{key1} . @var{value1})
2467 (@var{key2} . @var{value2})
2468 (@var{key3} . @var{value3})
2472 If an alist is a grob property or @code{\paper} variable, its keys
2473 can be modified individually without affecting other keys.
2475 For example, to reduce the space between adjacent staves in a
2476 staff-group, use the @code{staff-staff-spacing} property of the
2477 @code{StaffGrouper} grob. The property is an alist with four
2478 keys: @code{basic-distance}, @code{minimum-distance},
2479 @code{padding}, and @code{stretchability}. The standard settings
2480 for this property are listed in the @qq{Backend} section of the
2481 Internals Reference (see @rinternals{StaffGrouper}):
2484 '((basic-distance . 9)
2485 (minimum-distance . 7)
2487 (stretchability . 5))
2490 One way to bring the staves closer together is by reducing the
2491 value of the @code{basic-distance} key (@code{9}) to match the
2492 value of @code{minimum-distance} (@code{7}). To modify a single
2493 key individually, use a @emph{nested declaration}:
2495 @lilypond[quote,verbatim]
2496 % default space between staves
2498 \new Staff { \clef treble c''1 }
2499 \new Staff { \clef bass c1 }
2502 % reduced space between staves
2503 \new PianoStaff \with {
2504 % this is the nested declaration
2505 \override StaffGrouper.staff-staff-spacing.basic-distance = #7
2507 \new Staff { \clef treble c''1 }
2508 \new Staff { \clef bass c1 }
2512 Using a nested declaration will update the specified key (such as
2513 @code{basic-distance} in the above example) without altering any
2514 other keys already set for the same property.
2516 Now suppose we want the staves to be as close as possible without
2517 overlapping. The simplest way to do this is to set all four alist
2518 keys to zero. However, it is not necessary to enter four nested
2519 declarations, one for each key. Instead, the property can be
2520 completely re-defined with one declaration, as an alist:
2522 @lilypond[quote,verbatim]
2523 \new PianoStaff \with {
2524 \override StaffGrouper.staff-staff-spacing =
2525 #'((basic-distance . 0)
2526 (minimum-distance . 0)
2528 (stretchability . 0))
2530 \new Staff { \clef treble c''1 }
2531 \new Staff { \clef bass c1 }
2535 Note that any keys not explicitly listed in the alist definition
2536 will be reset to their @emph{default-when-unset} values. In the
2537 case of @code{staff-staff-spacing}, any unset key-values would be
2538 reset to zero (except @code{stretchability}, which takes the value
2539 of @code{basic-distance} when unset). Thus the following two
2540 declarations are equivalent:
2543 \override StaffGrouper.staff-staff-spacing =
2544 #'((basic-distance . 7))
2546 \override StaffGrouper.staff-staff-spacing =
2547 #'((basic-distance . 7)
2548 (minimum-distance . 0)
2550 (stretchability . 7))
2553 One (possibly unintended) consequence of this is the removal of
2554 any standard settings that are set in an initialization file and
2555 loaded each time an input file is compiled. In the above example,
2556 the standard settings for @code{padding} and
2557 @code{minimum-distance} (defined in @file{scm/define-grobs.scm})
2558 are reset to their default-when-unset values (zero for both keys).
2559 Defining a property or variable as an alist (of any size) will
2560 always reset all unset key-values to their default-when-unset
2561 values. Unless this is the intended result, it is safer to update
2562 key-values individually with a nested declaration.
2564 @warning{Nested declarations will not work for context property
2565 alists (such as @code{beamExceptions}, @code{keyAlterations},
2566 @code{timeSignatureSettings}, etc.). These properties can only be
2567 modified by completely re-defining them as alists.}
2570 @node Useful concepts and properties
2571 @section Useful concepts and properties
2576 * Direction and placement::
2577 * Distances and measurements::
2579 * Staff symbol properties::
2581 * Visibility of objects::
2583 * Rotating objects::
2587 @subsection Input modes
2589 The way in which the notation contained within an input file is
2590 interpreted is determined by the current input mode.
2592 @subsubsubheading Chord mode
2594 This is activated with the @code{\chordmode} command, and causes
2595 input to be interpreted with the syntax of chord notation, see
2596 @ref{Chord notation}. Chords are rendered as notes on a staff.
2598 Chord mode is also activated with the @code{\chords} command.
2599 This also creates a new @code{ChordNames} context and
2600 causes the following input to be interpreted with the syntax of
2601 chord notation and rendered as chord names in the @code{ChordNames}
2602 context, see @ref{Printing chord names}.
2604 @subsubsubheading Drum mode
2606 This is activated with the @code{\drummode} command, and causes
2607 input to be interpreted with the syntax of drum notation, see
2608 @ref{Basic percussion notation}.
2610 Drum mode is also activated with the @code{\drums} command.
2611 This also creates a new @code{DrumStaff} context and causes the
2612 following input to be interpreted with the syntax of drum notation
2613 and rendered as drum symbols on a drum staff, see
2614 @ref{Basic percussion notation}.
2616 @subsubsubheading Figure mode
2618 This is activated with the @code{\figuremode} command, and causes
2619 input to be interpreted with the syntax of figured bass, see
2620 @ref{Entering figured bass}.
2622 Figure mode is also activated with the @code{\figures} command.
2623 This also creates a new @code{FiguredBass} context and causes the
2624 following input to be interpreted with the figured bass syntax
2625 and rendered as figured bass symbols in the @code{FiguredBass}
2626 context, see @ref{Introduction to figured bass}.
2628 @subsubsubheading Fret and tab modes
2630 There are no special input modes for entering fret and tab symbols.
2632 To create tab diagrams, enter notes or chords in note mode and
2633 render them in a @code{TabStaff} context, see
2634 @ref{Default tablatures}.
2636 To create fret diagrams above a staff, you have two choices.
2637 You can either use the @code{FretBoards} context (see
2638 @ref{Automatic fret diagrams} or you can enter them as a markup
2639 above the notes using the @code{\fret-diagram} command (see
2640 @ref{Fret diagram markups}).
2642 @subsubsubheading Lyrics mode
2644 This is activated with the @code{\lyricmode} command, and causes
2645 input to be interpreted as lyric syllables with optional durations
2646 and associated lyric modifiers, see @ref{Vocal music}.
2648 Lyric mode is also activated with the @code{\addlyrics} command.
2649 This also creates a new @code{Lyrics} context and an implicit
2650 @code{\lyricsto} command which associates the following lyrics
2651 with the preceding music.
2653 @subsubsubheading Markup mode
2655 This is activated with the @code{\markup} command, and causes
2656 input to be interpreted with the syntax of markup, see
2657 @ref{Text markup commands}.
2659 @subsubsubheading Note mode
2661 This is the default mode or it may be activated with the
2662 @code{\notemode} command. Input is interpreted as pitches,
2663 durations, markup, etc and typeset as musical notation on a staff.
2665 It is not normally necessary to specify note mode explicitly, but
2666 it may be useful to do so in certain situations, for example if you
2667 are in lyric mode, chord mode or any other mode and want to insert
2668 something that only can be done with note mode syntax.
2671 @node Direction and placement
2672 @subsection Direction and placement
2674 In typesetting music the direction and placement of many items is
2675 a matter of choice. For example, the stems of notes can
2676 be directed up or down; lyrics, dynamics, and other expressive
2677 marks may be placed above or below the staff; text may be aligned
2678 left, right or center; etc. Most of these choices may be left to
2679 be determined automatically by LilyPond, but in some cases it may
2680 be desirable to force a particular direction or placement.
2683 * Articulation direction indicators::
2684 * The direction property::
2687 @node Articulation direction indicators
2688 @unnumberedsubsubsec Articulation direction indicators
2690 By default some directions are always up or always down (e.g.
2691 dynamics or fermata), while other things can alternate between
2692 up or down based on the stem direction (like slurs or accents).
2694 @c TODO Add table showing these
2696 The default action may be overridden by prefixing the articulation
2697 by a @emph{direction indicator}. Three direction indicators are
2698 available: @code{^} (meaning @qq{up}), @code{_} (meaning @qq{down})
2699 and @code{-} (meaning @qq{use default direction}). The direction
2700 indicator can usually be omitted, in which case @code{-} is assumed,
2701 but a direction indicator is @strong{always} required before
2704 @item @code{\tweak} commands
2705 @item @code{\markup} commands
2706 @item @code{\tag} commands
2707 @item string markups, e.g. -"string"
2708 @item fingering instructions, e.g. @w{@code{-1}}
2709 @item articulation shortcuts, e.g. @w{@code{-.}}, @w{@code{->}}, @w{@code{--}}
2712 Direction indicators affect only the next note:
2714 @lilypond[verbatim,quote]
2723 @node The direction property
2724 @unnumberedsubsubsec The direction property
2726 The position or direction of many layout objects is controlled by the
2727 @code{direction} property.
2729 The value of the @code{direction} property may be set to @code{1},
2730 meaning @qq{up} or @qq{above}, or to @w{@code{-1}}, meaning @qq{down} or
2731 @qq{below}. The symbols @code{UP} and @code{DOWN} may be used instead
2732 of @code{1} and @w{@code{-1}} respectively. The default direction may
2733 be specified by setting @code{direction} to @code{0} or @code{CENTER}.
2734 Alternatively, in many cases predefined commands exist to specify the
2735 direction. These are of the form
2738 @code{\xxxUp}, @code{\xxxDown} or @code{\xxxNeutral}
2742 where @code{\xxxNeutral} means @qq{use the default} direction.
2743 See @rlearning{Within-staff objects}.
2745 In a few cases, arpeggio for example, the value of the @code{direction}
2746 property can specify whether the object is to be placed to the right or
2747 left of the parent. In this case @w{@code{-1}} or @code{LEFT} means
2748 @qq{to the left} and @code{1} or @code{RIGHT} means @qq{to the right}.
2749 @code{0} or @code{CENTER} means @qq{use the default} direction.
2752 These all have side-axis set to #X
2753 AmbitusAccidental - direction has no effect
2755 StanzaNumber - not tried
2756 TrillPitchAccidental - not tried
2757 TrillPitchGroup - not tried
2760 These indications affect all notes until they are canceled.
2762 @lilypond[verbatim,quote]
2773 In polyphonic music, it is generally better to specify an explicit
2774 @code{voice} than change an object's direction. For more information.
2775 See @ref{Multiple voices}.
2779 @rlearning{Within-staff objects}.
2782 @ref{Multiple voices}.
2785 @node Distances and measurements
2786 @subsection Distances and measurements
2788 @cindex distances, absolute
2789 @cindex distances, scaled
2796 Distances in LilyPond are of two types: absolute and scaled.
2798 Absolute distances are used for specifying margins, indents, and
2799 other page layout details, and are by default specified in
2800 millimeters. Distances may be specified in other units by
2801 following the quantity by @code{\mm}, @code{\cm},
2802 @code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27 of
2803 an inch). Page layout distances can also be specified in scalable
2804 units (see the following paragraph) by appending
2805 @code{\staff-space} to the quantity. Page layout is described in
2806 detail in @ref{Page layout}.
2808 Scaled distances are always specified in units of the staff-space
2809 or, rarely, the half staff-space. The staff-space is the distance
2810 between two adjacent staff lines. The default value can be changed
2811 globally by setting the global staff size, or it can be overridden
2812 locally by changing the @code{staff-space} property of
2813 @code{StaffSymbol}. Scaled distances automatically scale with any
2814 change to the either the global staff size or the
2815 @code{staff-space} property of @code{StaffSymbol}, but fonts scale
2816 automatically only with changes to the global staff size.
2817 The global staff size thus enables the overall size of a rendered
2818 score to be easily varied. For the methods of setting the global
2819 staff size see @ref{Setting the staff size}.
2823 If just a section of a score needs to be rendered to a different
2824 scale, for example an ossia section or a footnote, the global staff
2825 size cannot simply be changed as this would affect the entire score.
2826 In such cases the change in size is made by overriding both the
2827 @code{staff-space} property of @code{StaffSymbol} and the size of
2828 the fonts. A Scheme function, @code{magstep}, is available to
2829 convert from a font size change to the equivalent change in
2830 @code{staff-space}. For an explanation and an example of its use,
2831 see @rlearning{Length and thickness of objects}.
2835 @rlearning{Length and thickness of objects}.
2839 @ref{Setting the staff size}.
2843 @subsection Dimensions
2846 @cindex bounding box
2848 The dimensions of a graphical object specify the positions of the left
2849 and right edges and the bottom and top edges of the objects' bounding
2850 box as distances from the objects' reference point in units of
2851 staff-spaces. These positions are usually coded as two Scheme pairs.
2852 For example, the text markup command @code{\with-dimensions} takes
2853 three arguments, the first two of which are a Scheme pair giving the
2854 left and right edge positions and a Scheme pair giving the bottom and
2858 \with-dimensions #'(-5 . 10) #'(-3 . 15) @var{arg}
2861 This specifies a bounding box for @var{arg} with its left edge at -5,
2862 its right edge at 10, its bottom edge at -3 and its top edge at 15,
2863 all measured from the objects' reference point in units of
2868 @ref{Distances and measurements}.
2871 @node Staff symbol properties
2872 @subsection Staff symbol properties
2874 @cindex adjusting staff symbol
2875 @cindex drawing staff symbol
2876 @cindex staff symbol, setting of
2878 @c TODO Extend or remove this section. See also NR 1.6.2 Staff symbol
2879 @c Need to think of uses for these properties. Eg 'line-positions
2880 @c is used in a snippet to thicken centre line.
2881 @c If retained, add @ref to here in 1.6.2 -td
2883 The vertical position of staff lines and the number of staff lines
2884 can be defined at the same time. As the following example shows,
2885 note positions are not influenced by the staff line positions.
2887 @warning{The @code{'line-positions} property overrides the
2888 @code{'line-count} property. The number of staff lines is
2889 implicitly defined by the number of elements in the list of values
2890 for @code{'line-positions}.}
2892 @lilypond[verbatim,quote]
2894 \override StaffSymbol.line-positions = #'(7 3 0 -4 -6 -7)
2896 \relative { a4 e' f b | d1 }
2899 The width of a staff can be modified. The units are staff
2900 spaces. The spacing of objects inside the staff is not affected by
2903 @lilypond[verbatim,quote]
2905 \override StaffSymbol.width = #23
2907 \relative { a4 e' f b | d1 }
2912 @subsection Spanners
2914 Many objects of musical notation extend over several notes or even
2915 several bars. Examples are slurs, beams, tuplet brackets, volta
2916 repeat brackets, crescendi, trills, and glissandi. Such objects
2917 are collectively called @qq{spanners}, and have special properties to control
2918 their appearance and behaviour. Some of these properties are common
2919 to all spanners; others are restricted to a sub-set of the spanners.
2921 All spanners support the @code{spanner-interface}. A few, essentially
2922 those that draw a straight line between the two objects, support in
2923 addition the @code{line-spanner-interface}.
2926 * Using the spanner-interface::
2927 * Using the line-spanner-interface::
2930 @node Using the spanner-interface
2931 @unnumberedsubsubsec Using the @code{spanner-interface}
2933 This interface provides two properties that apply to several spanners.
2935 @subsubsubheading The @code{minimum-length} property
2937 The minimum length of the spanner is specified by the
2938 @code{minimum-length} property. Increasing this usually has the
2939 necessary effect of increasing the spacing of the notes between the
2940 two end points. However, this override has no effect on
2941 many spanners, as their length is determined by other considerations.
2942 A few examples where it is effective are shown below.
2952 Works as long as callback is made:
2956 Works not at all for:
2965 @lilypond[verbatim,quote,fragment]
2968 % increase the length of the tie
2969 -\tweak minimum-length #5
2973 @lilypond[verbatim,quote]
2974 \relative \compressMMRests {
2977 % increase the length of the rest bar
2978 \once \override MultiMeasureRest.minimum-length = #20
2984 @lilypond[verbatim,quote]
2987 % increase the length of the hairpin
2988 \override Hairpin.minimum-length = #20
2993 This override can also be used to increase the length of slurs and
2996 @lilypond[verbatim,quote]
3000 -\tweak minimum-length #5
3005 -\tweak minimum-length #5
3010 For some layout objects, the @code{minimum-length} property becomes
3011 effective only if the @code{set-spacing-rods} procedure is called
3012 explicitly. To do this, the @code{springs-and-rods} property should
3013 be set to @code{ly:spanner::set-spacing-rods}. For example,
3014 the minimum length of a glissando has no effect unless the
3015 @code{springs-and-rods} property is set:
3017 @lilypond[verbatim,fragment,quote]
3021 % not effective alone
3022 \once \override Glissando.minimum-length = #20
3025 % effective only when both overrides are present
3026 \once \override Glissando.minimum-length = #20
3027 \once \override Glissando.springs-and-rods = #ly:spanner::set-spacing-rods
3031 The same is true of the @code{Beam} object:
3033 @lilypond[verbatim,fragment,quote]
3034 % not effective alone
3035 \once \override Beam.minimum-length = #20
3038 % effective only when both overrides are present
3039 \once \override Beam.minimum-length = #20
3040 \once \override Beam.springs-and-rods = #ly:spanner::set-spacing-rods
3044 @subsubsubheading The @code{to-barline} property
3046 The second useful property of the @code{spanner-interface} is
3047 @code{to-barline}. By default this is true, causing hairpins and
3048 other spanners which are terminated on the first note of a measure to
3049 end instead on the immediately preceding bar line. If set to false,
3050 the spanner will extend beyond the bar line and end on the note
3053 @lilypond[verbatim,quote]
3055 a' \< a a a a \! a a a \break
3056 \override Hairpin.to-barline = ##f
3057 a \< a a a a \! a a a
3061 This property is not effective for all spanners. For example,
3062 setting it to @code{#t} has no effect on slurs or phrasing slurs
3063 or on other spanners for which terminating on the bar line would
3066 @node Using the line-spanner-interface
3067 @unnumberedsubsubsec Using the @code{line-spanner-interface}
3069 Objects which support the @code{line-spanner-interface} include
3072 @item @code{DynamicTextSpanner}
3073 @item @code{Glissando}
3074 @item @code{TextSpanner}
3075 @item @code{TrillSpanner}
3076 @item @code{VoiceFollower}
3079 The routine responsible for drawing the stencils for these spanners is
3080 @code{ly:line-spanner::print}. This routine determines the
3081 exact location of the two end points and draws a line
3082 between them, in the style requested. The locations of the two
3083 end points of the spanner are computed on-the-fly, but it is
3084 possible to override their Y-coordinates. The
3085 properties which need to be specified are nested
3086 two levels down within the property hierarchy, but the syntax of
3087 the @code{\override} command is quite simple:
3089 @lilypond[quote,fragment,verbatim]
3091 \once \override Glissando.bound-details.left.Y = #3
3092 \once \override Glissando.bound-details.right.Y = #-2
3096 The units for the @code{Y} property are @code{staff-space}s,
3097 with the center line of the staff being the zero point.
3098 For the glissando, this is the value for @code{Y} at the
3099 X-coordinate corresponding to the center point of each note head,
3100 if the line is imagined to be extended to there.
3102 If @code{Y} is not set, the value is computed from the vertical
3103 position of the corresponding attachment point of the spanner.
3105 In case of a line break, the values for the end points are
3106 specified by the @code{left-broken} and @code{right-broken}
3107 sub-lists of @code{bound-details}. For example:
3109 @lilypond[ragged-right,fragment,verbatim,quote]
3110 \override Glissando.breakable = ##t
3111 \override Glissando.bound-details.right-broken.Y = #-3
3112 c''1 \glissando \break
3117 A number of further properties of the @code{left} and
3118 @code{right} sub-lists of the @code{bound-details} property
3119 may be modified in the same way as @code{Y}:
3123 This sets the Y-coordinate of the end point, in @code{staff-space}s
3124 offset from the staff center line. By default, it is the center of
3125 the bound object, so a glissando points to the vertical center of
3128 For horizontal spanners, such as text spanners and trill spanners,
3129 it is hardcoded to 0.
3132 This determines where the line starts and ends in the X-direction,
3133 relative to the bound object. So, a value of @w{@code{-1}} (or
3134 @code{LEFT}) makes the line start/end at the left side of the note
3135 head it is attached to.
3138 This is the absolute X-coordinate of the end point. It is usually
3139 computed on the fly, and overriding it has little useful effect.
3142 Line spanners may have symbols at the beginning or end, which is
3143 contained in this sub-property. This is for internal use; it is
3144 recommended that @code{text} be used instead.
3147 This is a markup that is evaluated to yield the stencil. It is used
3148 to put @i{cresc.}, @i{tr} and other text on horizontal spanners.
3150 @lilypond[quote,ragged-right,fragment,verbatim]
3151 \override TextSpanner.bound-details.left.text
3152 = \markup { \small \bold Slower }
3153 \relative { c''2\startTextSpan b c a\stopTextSpan }
3156 @item stencil-align-dir-y
3157 @item stencil-offset
3158 Without setting one of these, the stencil is simply put at the
3159 end-point, centered on the line, as defined by the @code{X} and
3160 @code{Y} sub-properties. Setting either @code{stencil-align-dir-y}
3161 or @code{stencil-offset} will move the symbol at the edge vertically
3162 relative to the end point of the line:
3164 @lilypond[quote,fragment,verbatim]
3165 \override TextSpanner.bound-details.left.stencil-align-dir-y = #-2
3166 \override TextSpanner.bound-details.right.stencil-align-dir-y = #UP
3168 \override TextSpanner.bound-details.left.text = #"ggg"
3169 \override TextSpanner.bound-details.right.text = #"hhh"
3171 \relative { c'4^\startTextSpan c c c \stopTextSpan }
3174 Note that negative values move the text @emph{up}, contrary to the
3175 effect that might be expected, as a value of @w{@code{-1}} or
3176 @code{DOWN} means align the @emph{bottom} edge of the text with
3177 the spanner line. A value of @code{1} or @code{UP} aligns
3178 the top edge of the text with the spanner line.
3181 Setting this sub-property to @code{#t} produces an arrowhead at the
3185 This sub-property controls the space between the specified
3186 end point of the line and the actual end. Without padding, a
3187 glissando would start and end in the center of each note head.
3191 The music function @code{\endSpanners} terminates the spanner
3192 which starts on the immediately following note prematurely. It
3193 is terminated after exactly one note, or at the following bar line
3194 if @code{to-barline} is true and a bar line occurs before the next
3197 @lilypond[verbatim,quote,ragged-right]
3200 c2 \startTextSpan c2 c2
3206 When using @code{\endSpanners} it is not necessary to close
3207 \startTextSpan with \stopTextSpan, nor is it necessary to close
3208 hairpins with @code{\!}.
3211 Internals Reference:
3212 @rinternals{TextSpanner},
3213 @rinternals{Glissando},
3214 @rinternals{VoiceFollower},
3215 @rinternals{TrillSpanner},
3216 @rinternals{line-spanner-interface}.
3219 @node Visibility of objects
3220 @subsection Visibility of objects
3222 @cindex objects, visibility of
3223 @cindex grobs, visibility of
3224 @cindex visibility of objects
3226 There are four main ways in which the visibility of layout objects
3227 can be controlled: their stencil can be removed, they can be made
3228 transparent, they can be colored white, or their
3229 @code{break-visibility} property can be overridden. The first
3230 three apply to all layout objects; the last to just a few -- the
3231 @emph{breakable} objects. The Learning Manual introduces these
3232 four techniques, see @rlearning{Visibility and color of objects}.
3234 There are also a few other techniques which are specific to
3235 certain layout objects. These are covered under Special
3239 * Removing the stencil::
3240 * Making objects transparent::
3241 * Painting objects white::
3242 * Using break-visibility::
3243 * Special considerations::
3247 @node Removing the stencil
3248 @unnumberedsubsubsec Removing the stencil
3250 @cindex stencil, removing
3253 Every layout object has a stencil property. By default this is set
3254 to the specific function which draws that object. If this property
3255 is overridden to @code{#f} no function will be called and the object
3256 will not be drawn. The default action can be recovered with
3259 @lilypond[quote,fragment,verbatim]
3261 \override Score.BarLine.stencil = ##f
3263 \revert Score.BarLine.stencil
3267 This rather common operation has a shortcut @code{\omit}:
3269 @lilypond[quote,fragment,verbatim]
3273 \undo \omit Score.BarLine
3277 @node Making objects transparent
3278 @unnumberedsubsubsec Making objects transparent
3280 @cindex transparent, making objects
3283 Every layout object has a transparent property which by default is
3284 set to @code{#f}. If set to @code{#t} the object still occupies
3285 space but is made invisible.
3287 @lilypond[quote,fragment,verbatim]
3289 \once \override NoteHead.transparent = ##t
3293 This rather common operation has a shortcut @code{\hide}:
3295 @lilypond[quote,fragment,verbatim]
3297 \once \hide NoteHead
3301 @node Painting objects white
3302 @unnumberedsubsubsec Painting objects white
3304 @cindex objects, coloring
3305 @cindex coloring objects
3307 @cindex printing order
3308 @cindex overwriting objects
3309 @cindex objects, overwriting
3310 @cindex grobs, overwriting
3312 Every layout object has a color property which by default is set
3313 to @code{black}. If this is overridden to @code{white} the object
3314 will be indistinguishable from the white background. However,
3315 if the object crosses other objects the color of the crossing
3316 points will be determined by the order in which they are drawn,
3317 and this may leave a ghostly image of the white object, as shown
3320 @lilypond[quote,fragment,verbatim]
3321 \override Staff.Clef.color = #white
3325 This may be avoided by changing the order of printing the objects.
3326 All layout objects have a @code{layer} property which should be set
3327 to an integer. Objects with the lowest value of @code{layer} are
3328 drawn first, then objects with progressively higher values are drawn,
3329 so objects with higher values overwrite objects with lower values.
3330 By default most objects are assigned a @code{layer} value of
3331 @code{1}, although a few objects, including @code{StaffSymbol} and
3332 @code{BarLine}, are assigned a value of @code{0}. The order of
3333 printing objects with the same value of @code{layer} is indeterminate.
3335 In the example above the white clef, with a default @code{layer}
3336 value of @code{1}, is drawn after the staff lines (default
3337 @code{layer} value @code{0}), so overwriting them. To change this,
3338 the @code{Clef} object must be given in a lower value of
3339 @code{layer}, say @w{@code{-1}}, so that it is drawn earlier:
3341 @lilypond[quote,fragment,verbatim]
3342 \override Staff.Clef.color = #white
3343 \override Staff.Clef.layer = #-1
3347 @node Using break-visibility
3348 @unnumberedsubsubsec Using break-visibility
3350 @c TODO Add making other objects breakable
3352 @cindex break-visibility
3354 Most layout objects are printed only once, but some like
3355 bar lines, clefs, time signatures and key signatures, may need
3356 to be printed twice when a line break occurs -- once at the end
3357 of the line and again at the start of the next line. Such
3358 objects are called @emph{breakable}, and have a property, the
3359 @code{break-visibility} property to control their visibility
3360 at the three positions in which they may appear -- at the
3361 start of a line, within a line if they are changed, and at the
3362 end of a line if a change takes place there.
3364 For example, the time signature
3365 by default will be printed at the start of the first line, but
3366 nowhere else unless it changes, when it will be printed at the
3367 point at which the change occurs. If this change occurs at the
3368 end of a line the new time signature will be printed at the start
3369 of the next line and a cautionary time signature will be printed
3370 at the end of the previous line as well.
3372 This behaviour is controlled by the @code{break-visibility}
3373 property, which is explained in
3374 @c Leave this ref on a newline - formats incorrectly otherwise -td
3375 @rlearning{Visibility and color of objects}. This property takes
3376 a vector of three booleans which, in order, determine whether the
3377 object is printed at the end of, within the body of, or at the
3378 beginning of a line. Or to be more precise, before a line break,
3379 where there is no line break, or after a line break.
3381 Alternatively, these eight combinations may be specified
3382 by pre-defined functions, defined in @file{scm/output-lib.scm},
3383 where the last three columns indicate whether the layout objects
3384 will be visible in the positions shown at the head of the columns:
3386 @multitable {@code{begin-of-line-invisible}} {@code{#(#t #t #t)}} {Before} {At no} {After}
3387 @headitem Function @tab Vector @tab Before @tab At no @tab After
3388 @headitem form @tab form @tab break @tab break @tab break
3390 @item @code{all-visible} @tab @code{#(#t #t #t)} @tab yes @tab yes @tab yes
3391 @item @code{begin-of-line-visible} @tab @code{#(#f #f #t)} @tab no @tab no @tab yes
3392 @item @code{center-visible} @tab @code{#(#f #t #f)} @tab no @tab yes @tab no
3393 @item @code{end-of-line-visible} @tab @code{#(#t #f #f)} @tab yes @tab no @tab no
3394 @item @code{begin-of-line-invisible} @tab @code{#(#t #t #f)} @tab yes @tab yes @tab no
3395 @item @code{center-invisible} @tab @code{#(#t #f #t)} @tab yes @tab no @tab yes
3396 @item @code{end-of-line-invisible} @tab @code{#(#f #t #t)} @tab no @tab yes @tab yes
3397 @item @code{all-invisible} @tab @code{#(#f #f #f)} @tab no @tab no @tab no
3400 The default settings of @code{break-visibility} depend on the
3401 layout object. The following table shows all the layout objects
3402 of interest which are affected by @code{break-visibility} and the
3403 default setting of this property:
3405 @multitable @columnfractions .3 .3 .4
3407 @headitem Layout object @tab Usual context @tab Default setting
3409 @c omit Ambitus as it appears not to be affected by break-visibility -td
3410 @c @item @code{Ambitus} @tab as specified @tab @code{begin-of-line-visible}
3411 @item @code{BarLine} @tab @code{Score} @tab calculated
3412 @item @code{BarNumber} @tab @code{Score} @tab @code{begin-of-line-visible}
3413 @c omit the following item until it can be explained -td
3414 @c @item @code{BreakAlignGroup} @tab @code{Score} @tab calculated
3415 @item @code{BreathingSign} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3416 @item @code{Clef} @tab @code{Staff} @tab @code{begin-of-line-visible}
3417 @item @code{Custos} @tab @code{Staff} @tab @code{end-of-line-visible}
3418 @item @code{DoublePercentRepeat} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3419 @item @code{KeyCancellation} @tab @code{Staff} @tab @code{begin-of-line-invisible}
3420 @item @code{KeySignature} @tab @code{Staff} @tab @code{begin-of-line-visible}
3421 @c omit LeftEdge until it can be explained -td
3422 @c @item @code{LeftEdge} @tab @code{Score} @tab @code{center-invisible}
3423 @item @code{ClefModifier} @tab @code{Staff} @tab @code{begin-of-line-visible}
3424 @item @code{RehearsalMark} @tab @code{Score} @tab @code{end-of-line-invisible}
3425 @item @code{TimeSignature} @tab @code{Staff} @tab @code{all-visible}
3429 The example below shows the use of the vector form to control the
3430 visibility of bar lines:
3432 @lilypond[quote,verbatim,ragged-right]
3436 % Remove bar line at the end of the current line
3437 \once \override Score.BarLine.break-visibility = ##(#f #t #t)
3444 Although all three components of the vector used to override
3445 @code{break-visibility} must be present, not all of them are
3446 effective with every layout object, and some combinations may
3447 even give errors. The following limitations apply:
3450 @item Bar lines cannot be printed at start of line.
3451 @item A bar number cannot be printed at the start of the first
3452 line unless it is set to be different from 1.
3453 @item Clef -- see below
3454 @item Double percent repeats are either all printed or all
3455 suppressed. Use begin-of line-invisible to print and
3456 all-invisible to suppress.
3457 @item Key signature -- see below
3458 @item ClefModifier -- see below
3461 @node Special considerations
3462 @unnumberedsubsubsec Special considerations
3464 @subsubsubheading Visibility following explicit changes
3466 @cindex key signature, visibility following explicit change
3467 @cindex explicitKeySignatureVisibility
3468 @cindex clef, visibility following explicit change
3469 @cindex explicitClefVisibility
3471 The @code{break-visibility} property controls the visibility of
3472 key signatures and changes of clef only at the start of lines,
3473 i.e. after a break. It has no effect on the visibility of the
3474 key signature or clef following an explicit key change or an
3475 explicit clef change within or at the end of a line. In the
3476 following example the key signature following the explicit change
3477 to B-flat major is still visible, even though @code{all-invisible}
3480 @lilypond[quote,verbatim,ragged-right]
3484 % Try to remove all key signatures
3485 \override Staff.KeySignature.break-visibility = #all-invisible
3494 The visibility of such explicit key signature and clef changes is
3495 controlled by the @code{explicitKeySignatureVisibility} and
3496 @code{explicitClefVisibility} properties. These are the equivalent
3497 of the @code{break-visibility} property and both take a vector of
3498 three booleans or the predefined functions listed above, exactly like
3499 @code{break-visibility}. Both are properties of the Staff context,
3500 not the layout objects themselves, and so they are set using the
3501 @code{\set} command. Both are set by default to @code{all-visible}.
3502 These properties control only the visibility of key signatures and
3503 clefs resulting from explicit changes and do not affect key
3504 signatures and clefs at the beginning of lines;
3505 @code{break-visibility} must still be overridden in the appropriate
3506 object to remove these.
3508 @lilypond[quote,verbatim,ragged-right]
3512 \set Staff.explicitKeySignatureVisibility = #all-invisible
3513 \override Staff.KeySignature.break-visibility = #all-invisible
3521 @subsubsubheading Visibility of cancelling accidentals
3523 To remove the cancelling accidentals printed at an explicit key
3524 change, set the Staff context property @code{printKeyCancellation}
3527 @lilypond[quote,verbatim,ragged-right]
3531 \set Staff.explicitKeySignatureVisibility = #all-invisible
3532 \set Staff.printKeyCancellation = ##f
3533 \override Staff.KeySignature.break-visibility = #all-invisible
3541 With these overrides only the accidentals before the notes remain
3542 to indicate the change of key.
3544 Note that when changing the key to C@tie{}major or A@tie{}minor
3545 the cancelling accidentals would be the @emph{only} indication of
3546 the key change. In this case setting @code{printKeyCancellation} to
3547 @code{#f} has no effect:
3549 @lilypond[quote,verbatim,ragged-right]
3553 \set Staff.explicitKeySignatureVisibility = #all-invisible
3554 \set Staff.printKeyCancellation = ##f
3562 To suppress the cancelling accidentals even when the key is
3563 changed to C@tie{}major or A@tie{}minor, override
3564 the visibility of the @code{KeyCancellation} grob instead:
3566 @lilypond[quote,verbatim,ragged-right]
3570 \set Staff.explicitKeySignatureVisibility = #all-invisible
3571 \override Staff.KeyCancellation.break-visibility = #all-invisible
3579 @c TODO Add visibility of cautionary accidentals before notes
3581 @subsubsubheading Automatic bars
3583 @cindex automaticBars
3584 @cindex bar lines, suppressing
3586 As a special case, the printing of bar lines can also be turned off
3587 by setting the @code{automaticBars} property in the Score context.
3588 If set to @code{#f}, bar lines will not be printed automatically;
3589 they must be explicitly created with a @code{\bar} command. Unlike
3590 the @code{\cadenzaOn} predefined command, measures are still counted.
3591 Bar generation will resume according to that count if this property
3592 is later set to @code{#t}. When set to @code{#f}, line breaks can
3593 occur only at explicit @code{\bar} commands.
3597 @subsubsubheading Transposed clefs
3599 @cindex transposed clefs, visibility of
3600 @cindex visibility of transposed clefs
3601 @cindex clefs, visibility of transposition
3603 The small transposition symbol on transposed clefs is produced by the
3604 @code{ClefModifier} layout object. Its visibility is automatically
3605 inherited from the @code{Clef} object, so it is not necessary to apply
3606 any required @code{break-visibility} overrides to the @code{ClefModifier}
3607 layout objects to suppress transposition symbols for invisible clefs.
3609 For explicit clef changes, the @code{explicitClefVisibility}
3610 property controls both the clef symbol and any transposition symbol
3615 @rlearning{Visibility and color of objects}.
3619 @subsection Line styles
3621 Some performance indications, e.g., @i{rallentando} and
3622 @i{accelerando} and @i{trills} are written as text and are
3623 extended over many measures with lines, sometimes dotted or wavy.
3625 These all use the same routines as the glissando for drawing the
3626 texts and the lines, and tuning their behavior is therefore also
3627 done in the same way. It is done with a spanner, and the routine
3628 responsible for drawing the spanners is
3629 @code{ly:line-spanner::print}. This routine determines the
3630 exact location of the two @i{span points} and draws a line
3631 between them, in the style requested.
3633 Here is an example showing the different line styles available,
3634 and how to tune them.
3636 @lilypond[ragged-right,verbatim,quote]
3639 \once \override Glissando.style = #'dashed-line
3641 \override Glissando.style = #'dotted-line
3643 \override Glissando.style = #'zigzag
3645 \override Glissando.style = #'trill
3650 The locations of the end-points of the spanner are computed
3651 on-the-fly for every graphic object, but it is possible to
3655 @lilypond[ragged-right,verbatim,quote]
3658 \once \override Glissando.bound-details.right.Y = #-2
3663 The value for @code{Y} is set to @w{@code{-2}} for the right end
3664 point. The left side may be similarly adjusted by specifying
3665 @code{left} instead of @code{right}.
3667 If @code{Y} is not set, the value is computed from the vertical
3668 position of the left and right attachment points of the spanner.
3670 Other adjustments of spanners are possible, for details, see
3673 @node Rotating objects
3674 @subsection Rotating objects
3676 Both layout objects and elements of markup text can be rotated by
3677 any angle about any point, but the method of doing so differs.
3680 * Rotating layout objects::
3684 @node Rotating layout objects
3685 @unnumberedsubsubsec Rotating layout objects
3687 @cindex rotating objects
3688 @cindex objects, rotating
3690 All layout objects which support the @code{grob-interface} can be
3691 rotated by setting their @code{rotation} property. This takes a
3692 list of three items: the angle of rotation counter-clockwise,
3693 and the x and y coordinates of the point relative to the object's
3694 reference point about which the rotation is to be performed. The
3695 angle of rotation is specified in degrees and the coordinates in
3698 The angle of rotation and the coordinates of the rotation point must
3699 be determined by trial and error.
3701 @cindex hairpins, angled
3702 @cindex angled hairpins
3704 There are only a few situations where the rotation of layout
3705 objects is useful; the following example shows one situation where
3708 @lilypond[quote,fragment,verbatim]
3710 \override Hairpin.rotation = #'(20 -1 0)
3714 @node Rotating markup
3715 @unnumberedsubsubsec Rotating markup
3717 All markup text can be rotated to lie at any angle by prefixing it
3718 with the @code{\rotate} command. The command takes two arguments:
3719 the angle of rotation in degrees counter-clockwise and the text to
3720 be rotated. The extents of the text are not rotated: they take
3721 their values from the extremes of the x and y coordinates of the
3722 rotated text. In the following example the
3723 @code{outside-staff-priority} property for text is set to @code{#f}
3724 to disable the automatic collision avoidance, which would push some
3725 of the text too high.
3727 @lilypond[quote,fragment,verbatim]
3728 \override TextScript.outside-staff-priority = ##f
3729 g4^\markup { \rotate #30 "a G" }
3730 b^\markup { \rotate #30 "a B" }
3731 des'^\markup { \rotate #30 "a D-Flat" }
3732 fis'^\markup { \rotate #30 "an F-Sharp" }
3735 @node Advanced tweaks
3736 @section Advanced tweaks
3738 This section discusses various approaches to fine tuning the
3739 appearance of the printed score.
3742 * Aligning objects::
3743 * Vertical grouping of grobs::
3744 * Modifying stencils::
3745 * Modifying shapes::
3746 * Modifying broken spanners::
3747 * Unpure-pure containers::
3752 @rlearning{Tweaking output},
3753 @rlearning{Other sources of information}.
3756 @ref{Explaining the Internals Reference},
3757 @ref{Modifying properties}.
3760 @rextend{Interfaces for programmers}.
3763 @file{scm/define-grobs.scm}.
3766 @rlsr{Tweaks and overrides}.
3768 Internals Reference:
3769 @rinternals{All layout objects}.
3772 @node Aligning objects
3773 @subsection Aligning objects
3775 Graphical objects which support the @code{self-alignment-interface}
3776 and/or the @code{side-position-interface} can be aligned to a previously
3777 placed object in a variety of ways. For a list of these objects, see
3778 @rinternals{self-alignment-interface} and @rinternals{side-position-interface}.
3780 All graphical objects have a reference point, a horizontal extent and a
3781 vertical extent. The horizontal extent is a pair of numbers
3782 giving the displacements from the reference point of the left and
3783 right edges, displacements to the left being negative. The vertical
3784 extent is a pair of numbers giving the displacement from the reference
3785 point to the bottom and top edges, displacements down being negative.
3787 An object's position on a staff is given by the values of the
3788 @code{X-offset} and @code{Y-offset} properties. The value of
3789 @code{X-offset} gives the displacement from the X coordinate of
3790 the reference point of the parent object, and the value of
3791 @code{Y-offset} gives the displacement from the center line of the
3792 staff. The values of @code{X-offset} and @code{Y-offset} may
3793 be set directly or may be set to be calculated by procedures in order
3794 to achieve alignment with the parent object.
3796 @warning{Many objects have special positioning considerations which
3797 cause any setting of @code{X-offset} or @code{Y-offset} to be
3798 ignored or modified, even though the object supports the
3799 @code{self-alignment-interface}. Overriding the @code{X-offset}
3800 or @code{Y-offset} properties to a fixed value causes the respective
3801 @code{self-alignment} property to be disregarded.}
3803 For example, an accidental can be repositioned vertically by setting
3804 @code{Y-offset} but any changes to @code{X-offset} have no effect.
3806 Rehearsal marks may be aligned with breakable objects such as bar
3807 lines, clef symbols, time signature symbols and key signatures. There
3808 are special properties to be found in the @code{break-aligned-interface}
3809 for positioning rehearsal marks on such objects.
3813 @ref{Using the break-alignable-interface}.
3816 @rextend{Callback functions}.
3819 * Setting X-offset and Y-offset directly::
3820 * Using the side-position-interface::
3821 * Using the self-alignment-interface::
3822 * Using the break-alignable-interface::
3825 @node Setting X-offset and Y-offset directly
3826 @unnumberedsubsubsec Setting @code{X-offset} and @code{Y-offset} directly
3828 Numerical values may be given to the @code{X-offset} and @code{Y-offset}
3829 properties of many objects. The following example shows three
3830 notes with the default fingering position and the positions with @code{X-offset}
3831 and @code{Y-offset} modified.
3833 @lilypond[verbatim,fragment,quote]
3840 -\tweak X-offset #-1
3847 @node Using the side-position-interface
3848 @unnumberedsubsubsec Using the @code{side-position-interface}
3850 An object which supports the @code{side-position-interface} can be
3851 placed next to its parent object so that
3852 the specified edges of the two objects touch. The object may be
3853 placed above, below, to the right or to the left of the parent.
3854 The parent cannot be specified; it is determined by the order of
3855 elements in the input stream. Most objects have the associated
3856 note head as their parent.
3858 The values of the @code{side-axis} and @code{direction} properties
3859 determine where the object is to be placed, as follows:
3861 @c TODO add an example of each to the table
3863 @multitable @columnfractions .3 .3 .3
3864 @headitem @code{side-axis} @tab @code{direction} @tab
3865 @headitem property @tab property @tab Placement
3867 @item @code{0} @tab @code{-1} @tab left
3868 @item @code{0} @tab @code{1} @tab right
3869 @item @code{1} @tab @code{-1} @tab below
3870 @item @code{1} @tab @code{1} @tab above
3874 When @code{side-axis} is @code{0}, @code{X-offset} should be set to
3875 the procedure @code{ly:side-position-interface::x-aligned-side}.
3876 This procedure will return the correct value of @code{X-offset} to
3877 place the object to the left or right side of the parent according
3878 to value of @code{direction}.
3880 When @code{side-axis} is @code{1}, @code{Y-offset} should be set to
3881 the procedure @code{ly:side-position-interface::y-aligned-side}.
3882 This procedure will return the correct value of @code{Y-offset} to
3883 place the object to the top or bottom of the parent according
3884 to value of @code{direction}.
3886 @c TODO Add examples
3888 @node Using the self-alignment-interface
3889 @unnumberedsubsubsec Using the @code{self-alignment-interface}
3891 @subsubsubheading Self-aligning objects horizontally
3893 The horizontal alignment of an object which supports the
3894 @code{self-alignment-interface} is controlled by the value of
3895 the @code{self-alignment-X} property, provided the object's
3896 @code{X-offset} property is set to
3897 @code{ly:self-alignment-interface::x-aligned-on-self}.
3898 @code{self-alignment-X} may be given any
3899 real value, in units of half the total X extent of the
3900 object. Negative values move the object to the right, positive
3901 to the left. A value of @code{0} centers the object on the
3902 reference point of its parent, a value of @w{@code{-1}} aligns the
3903 left edge of the object on the reference point of its parent,
3904 and a value of @code{1} aligns the right edge of the object on the
3905 reference point of its parent. The symbols @code{LEFT},
3906 @code{CENTER}, and @code{RIGHT} may be used instead of the values
3907 @w{@code{-1}}, @code{0}, and @code{1}, respectively.
3909 Normally the @code{\override} command would be used to modify the
3910 value of @code{self-alignment-X}, but the @code{\tweak} command
3911 can be used to separately align several annotations on a single
3914 @lilypond[quote,verbatim,fragment]
3916 -\tweak self-alignment-X #-1
3918 -\tweak self-alignment-X #0
3920 -\tweak self-alignment-X #RIGHT
3922 -\tweak self-alignment-X #-2.5
3923 ^"aligned further to the right"
3926 @subsubsubheading Self-aligning objects vertically
3928 Objects may be aligned vertically in an analogous way to aligning
3929 them horizontally if the @code{Y-offset} property is set to
3930 @code{ly:self-alignment-interface::y-aligned-on-self}. However,
3931 other mechanisms are often involved in vertical alignment: the
3932 value of @code{Y-offset} is just one variable taken into account.
3933 This may make adjusting the value of some objects tricky.
3934 The units are just half the vertical extent of the object, which
3935 is usually quite small, so quite large numbers may be required.
3936 A value of @w{@code{-1}} aligns the lower edge of the object with
3937 the reference point of the parent object, a value of @code{0}
3938 aligns the center of the object with the reference point of the
3939 parent, and a value of @code{1} aligns the top edge of the object
3940 with the reference point of the parent. The symbols @code{DOWN},
3941 @code{CENTER}, and @code{UP} may be substituted for @w{@code{-1}},
3942 @code{0}, and @code{1}, respectively.
3944 @subsubsubheading Self-aligning objects in both directions
3946 By setting both @code{X-offset} and @code{Y-offset}, an object may
3947 be aligned in both directions simultaneously.
3949 The following example shows how to adjust a fingering mark so
3950 that it nestles close to the note head.
3952 @lilypond[quote,verbatim,fragment]
3954 -\tweak self-alignment-X #0.5 % move horizontally left
3955 -\tweak Y-offset #ly:self-alignment-interface::y-aligned-on-self
3956 -\tweak self-alignment-Y #-1 % move vertically up
3961 @unnumberedsubsubsec Using the @code{aligned-on-parent} procedures
3963 @c Cannot document as they do not seem to operate consistently on all objects -td
3964 @c TODO investigate further
3966 The @code{aligned-on-parent} procedures are used in the same way
3967 as the @code{aligned-on-self} procedures, they difference being
3968 that they permit an object to be aligned with the @emph{edges} of
3969 the parent rather than the parent's reference point. The following
3970 example shows the difference:
3974 @lilypond[verbatim,quote]
3980 @unnumberedsubsubsec Using the @code{centered-on-parent} procedures
3982 @c Cannot document as they do not seem to operate consistently on all objects -td
3983 @c TODO investigate further
3987 @c TODO The align-interface, BassFigureAlignment and VerticalAlignment
3989 @node Using the break-alignable-interface
3990 @unnumberedsubsubsec Using the @code{break-alignable-interface}
3992 @cindex align to objects
3993 @cindex break-align-symbols
3995 Rehearsal marks and bar numbers may be aligned with notation
3996 objects other than bar lines. These objects include @code{ambitus},
3997 @code{breathing-sign}, @code{clef}, @code{custos}, @code{staff-bar},
3998 @code{left-edge}, @code{key-cancellation}, @code{key-signature}, and
3999 @code{time-signature}.
4001 Each type of object has its own default reference point, to which
4002 rehearsal marks are aligned:
4004 @lilypond[verbatim,quote,fragment]
4005 % The rehearsal mark will be aligned to the right edge of the Clef
4006 \override Score.RehearsalMark.break-align-symbols = #'(clef)
4011 % The rehearsal mark will be aligned to the left edge of the Time Signature
4012 \override Score.RehearsalMark.break-align-symbols = #'(time-signature)
4018 % The rehearsal mark will be centered above the Breath Mark
4019 \override Score.RehearsalMark.break-align-symbols = #'(breathing-sign)
4028 A list of possible target alignment objects may be specified. If
4029 some of the objects are invisible at that point due to the setting
4030 of @code{break-visibility} or the explicit visibility settings for
4031 keys and clefs, the rehearsal mark or bar number is aligned to the
4032 first object in the list which is visible. If no objects in the
4033 list are visible the object is aligned to the bar line. If the bar
4034 line is invisible the object is aligned to the place where the bar
4037 @lilypond[verbatim,quote,fragment]
4038 % The rehearsal mark will be aligned to the right edge of the Key Signature
4039 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4044 % The rehearsal mark will be aligned to the right edge of the Clef
4045 \set Staff.explicitKeySignatureVisibility = #all-invisible
4046 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4051 % The rehearsal mark will be centered above the Bar Line
4052 \set Staff.explicitKeySignatureVisibility = #all-invisible
4053 \set Staff.explicitClefVisibility = #all-invisible
4054 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4061 The alignment of the rehearsal mark relative to the notation object
4062 can be changed, as shown in the following example. In a score with
4063 multiple staves, this setting should be done for all the staves.
4065 @lilypond[verbatim,quote,fragment]
4066 % The RehearsalMark will be aligned with the right edge of the Key Signature
4067 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4073 % The RehearsalMark will be centered above the Key Signature
4074 \once \override Score.KeySignature.break-align-anchor-alignment = #CENTER
4078 % The RehearsalMark will be aligned with the left edge of the Key Signature
4079 \once \override Score.KeySignature.break-align-anchor-alignment = #LEFT
4085 The rehearsal mark can also be offset to the right or left of the left
4086 edge by an arbitrary amount. The units are staff-spaces:
4088 @lilypond[verbatim,quote,fragment]
4089 % The RehearsalMark will be aligned with the left edge of the Key Signature
4090 % and then shifted right by 3.5 staff-spaces
4091 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4092 \once \override Score.KeySignature.break-align-anchor = #3.5
4096 % The RehearsalMark will be aligned with the left edge of the Key Signature
4097 % and then shifted left by 2 staff-spaces
4098 \once \override Score.KeySignature.break-align-anchor = #-2
4105 @node Vertical grouping of grobs
4106 @subsection Vertical grouping of grobs
4108 @c TODO Expand this section
4110 The VerticalAlignment and VerticalAxisGroup grobs work together.
4111 VerticalAxisGroup groups together different grobs like Staff, Lyrics,
4112 etc. VerticalAlignment then vertically aligns the different grobs
4113 grouped together by VerticalAxisGroup. There is usually only one
4114 VerticalAlignment per score but every Staff, Lyrics, etc. has its own
4118 @node Modifying stencils
4119 @subsection Modifying stencils
4121 All layout objects have a @code{stencil} property which is part of
4122 the @code{grob-interface}. By default, this property is usually
4123 set to a function specific to the object that is tailor-made to
4124 render the symbol which represents it in the output. For example,
4125 the standard setting for the @code{stencil} property of the
4126 @code{MultiMeasureRest} object is @code{ly:multi-measure-rest::print}.
4128 The standard symbol for any object can be replaced by modifying the
4129 @code{stencil} property to reference a different, specially-written,
4130 procedure. This requires a high level of knowledge of the internal
4131 workings of LilyPond, but there is an easier way which can often
4132 produce adequate results.
4134 This is to set the @code{stencil} property to the procedure which
4135 prints text -- @code{ly:text-interface::print} -- and to add a
4136 @code{text} property to the object which is set to contain the
4137 markup text which produces the required symbol. Due to the
4138 flexibility of markup, much can be achieved -- see in particular
4139 @ref{Graphic notation inside markup}.
4141 The following example demonstrates this by changing the note head
4142 symbol to a cross within a circle.
4144 @lilypond[verbatim,quote]
4146 \once \override NoteHead.stencil = #ly:text-interface::print
4147 \once \override NoteHead.text = \markup {
4149 \halign #-0.7 \draw-circle #0.85 #0.2 ##f
4150 \musicglyph #"noteheads.s2cross"
4158 Any of the glyphs in the feta Font can be supplied to the
4159 @code{\musicglyph} markup command -- see @ref{The Feta font}.
4161 @c TODO Add inserting eps files or ref to later
4163 @c TODO Add inserting Postscript or ref to later
4167 @ref{Graphic notation inside markup},
4168 @ref{Formatting text},
4169 @ref{Text markup commands},
4170 @ref{The Feta font}.
4173 @node Modifying shapes
4174 @subsection Modifying shapes
4177 * Modifying ties and slurs::
4180 @node Modifying ties and slurs
4181 @unnumberedsubsubsec Modifying ties and slurs
4183 @cindex slurs, modifying
4184 @cindex ties, modifying
4185 @cindex Bézier curves, control points
4186 @cindex control points, Bézier curves
4188 @code{Tie}s, @code{Slur}s, @code{PhrasingSlur}s,
4189 @code{LaissezVibrerTie}s and @code{RepeatTie}s are all drawn as
4190 third-order Bézier curves. If the shape of the tie or slur which
4191 is calculated automatically is not optimum, the shape may be
4192 modified manually in two ways:
4196 by specifying the displacements to be made to the control points
4197 of the automatically calculated Bézier curve, or
4200 by explicitly specifying the positions of the four control points
4201 required to define the wanted curve.
4204 Both methods are explained below. The first method is more suitable
4205 if only slight adjustments to the curve are required; the second may
4206 be better for creating curves which are related to just a single
4209 @subsubsubheading Cubic Bézier curves
4211 Third-order or cubic Bézier curves are defined by four control
4212 points. The first and fourth control points are precisely the
4213 starting and ending points of the curve. The intermediate two
4214 control points define the shape. Animations showing how the curve
4215 is drawn can be found on the web, but the following description
4216 may be helpful. The curve starts from the first control point
4217 heading directly towards the second, gradually bending over to
4218 head towards the third and continuing to bend over to head towards
4219 the fourth, arriving there travelling directly from the third
4220 control point. The curve is entirely contained in the
4221 quadrilateral defined by the four control points. Translations,
4222 rotations and scaling of the control points all result in exactly
4223 the same operations on the curve.
4225 @subsubsubheading Specifying displacements from current control points
4227 @cindex shaping slurs and ties
4230 In this example the automatic placement of the tie is not optimum,
4231 and @code{\tieDown} would not help.
4233 @lilypond[verbatim,quote]
4237 \relative { r4 <g' c,> <g c,> <g c,> }
4241 Adjusting the control points of the tie with @code{\shape} allows
4242 the collisions to be avoided.
4244 The syntax of @code{\shape} is
4247 [-]@code{\shape} @var{displacements} @var{item}
4250 This will reposition the control-points of @var{item} by the amounts
4251 given by @var{displacements}. The @var{displacements} argument is a
4252 list of number pairs or a list of such lists. Each element of a pair
4253 represents the displacement of one of the coordinates of a
4254 control-point. If @var{item} is a string, the result is
4255 @code{\once\override} for the specified grob type. If @var{item} is
4256 a music expression, the result is the same music expression with an
4257 appropriate tweak applied.
4259 In other words, the @code{\shape} function can act as either a
4260 @code{\once\override} command or a @code{\tweak} command depending
4261 on whether the @var{item} argument is a grob name, like @qq{Slur},
4262 or a music expression, like @qq{(}. The @var{displacements} argument
4263 specifies the displacements of the four control points as a list of
4264 four pairs of (dx . dy) values in units of staff-spaces (or a list
4265 of such lists if the curve has more than one segment).
4267 The leading hyphen is required if and only if the @code{\tweak} form
4270 So, using the same example as above and the @code{\once\override}
4271 form of @code{\shape}, this will raise the tie by half a staff-space:
4273 @lilypond[verbatim,quote]
4276 \shape #'((0 . 0.5) (0 . 0.5) (0 . 0.5) (0 . 0.5)) Tie
4280 \relative { r4 <g' c,> <g c,> <g c,> }
4284 This positioning of the tie is better, but maybe it should be raised
4285 more in the center. The following example does this, this time using
4286 the alternative @code{\tweak} form:
4288 @lilypond[verbatim,quote]
4291 e'1-\shape #'((0 . 0.5) (0 . 1) (0 . 1) (0 . 0.5)) ~ e'
4294 \relative { r4 <g' c,> <g c,> <g c,> }
4298 Changes to the horizontal positions of the control points may be made
4299 in the same way, and two different curves starting at the same
4300 musical moment may also be shaped:
4302 @lilypond[verbatim,quote,ragged-right]
4304 c''8(\( a) a'4 e c\)
4305 \shape #'((0.7 . -0.4) (0.5 . -0.4) (0.3 . -0.3) (0 . -0.2)) Slur
4306 \shape #'((0 . 0) (0 . 0.5) (0 . 0.5) (0 . 0)) PhrasingSlur
4311 The @code{\shape} function can also displace the control points of
4312 curves which stretch across line breaks. Each piece of the broken
4313 curve can be given its own list of offsets. If changes to a
4314 particular segment are not needed, the empty list can serve as a
4315 placeholder. In this example the line break makes the single slur
4318 @lilypond[verbatim,quote,ragged-right]
4326 Changing the shapes of the two halves of the slur makes it clearer
4327 that the slur continues over the line break:
4329 @lilypond[verbatim,quote,ragged-right]
4330 % () may be used as a shorthand for ((0 . 0) (0 . 0) (0 . 0) (0 . 0))
4331 % if any of the segments does not need to be changed
4334 (( 0 . 0) (0 . 0) (0 . 0) (0 . 1))
4335 ((0.5 . 1.5) (1 . 0) (0 . 0) (0 . -1.5))
4343 If an S-shaped curve is required the control points must always be
4344 adjusted manually --- LilyPond will never select such shapes
4347 @lilypond[verbatim,quote]
4349 c8( e b-> f d' a e-> g)
4350 \shape #'((0 . -1) (5.5 . -0.5) (-5.5 . -10.5) (0 . -5.5)) PhrasingSlur
4351 c8\( e b-> f d' a e-> g\)
4355 @subsubsubheading Specifying control points explicitly
4357 The coordinates of the Bézier control points are specified in units
4358 of staff-spaces. The X@tie{}coordinate is relative to the reference
4359 point of the note to which the tie or slur is attached, and the
4360 Y@tie{}coordinate is relative to the staff center line. The
4361 coordinates are specified as a list of four pairs of decimal numbers
4362 (reals). One approach is to estimate the coordinates of the two
4363 end points, and then guess the two intermediate points. The optimum
4364 values are then found by trial and error. Be aware that these values
4365 may need to be manually adjusted if any further changes are made to
4366 the music or the layout.
4368 One situation where specifying the control points explicitly is
4369 preferable to specifying displacements is when they need to be
4370 specified relative to a single note. Here is an example of this.
4371 It shows one way of indicating a slur extending into alternative
4372 sections of a volta repeat.
4374 @lilypond[verbatim,quote]
4377 \repeat volta 3 { c4 d( e f }
4382 % create a slur and move it to a new position
4383 % the <> is just an empty chord to carry the slur termination
4384 -\tweak control-points #'((-2 . 3.8) (-1 . 3.9) (0 . 4) (1 . 3.4)) ( <> )
4389 % create a slur and move it to a new position
4390 -\tweak control-points #'((-2 . 3) (-1 . 3.1) (0 . 3.2) (1 . 2.4)) ( <> )
4398 It is not possible to modify shapes of ties or slurs by changing
4399 the @code{control-points} property if there are multiple ties or slurs
4400 at the same musical moment -- the @code{\tweak} command will also not
4401 work in this case. However, the @code{tie-configuration} property of
4402 @code{TieColumn} can be overridden to set start line and direction as
4406 Internals Reference:
4407 @rinternals{TieColumn}.
4410 @node Modifying broken spanners
4411 @subsection Modifying broken spanners
4414 * Using alterBroken::
4417 @node Using alterBroken
4418 @unnumberedsubsubsec Using @code{\alterBroken}
4420 @cindex spanners, modifying
4421 @cindex broken spanners, modifying
4422 @funindex \alterBroken
4424 When a spanner crosses a line break or breaks, each piece
4425 inherits the attributes of the original spanner. Thus, ordinary
4426 tweaking of a broken spanner applies the same modifications to
4427 each of its segments. In the example below, overriding
4428 @code{thickness} affects the slur on either side of the line
4431 @lilypond[verbatim,quote,ragged-right]
4434 \once\override Slur.thickness = 10
4441 Independently modifying the appearance of individual pieces
4442 of a broken spanner is possible with the @code{\alterBroken}
4443 command. This command can produce either an @code{\override}
4444 or a @code{\tweak} of a spanner property.
4446 The syntax for @code{\alterBroken} is
4449 [-]@code{\alterBroken} @var{property} @var{values} @var{item}
4452 The argument @var{values} is a list of values, one for each
4453 broken piece. If @var{item} is a grob name like @code{Slur} or
4454 @code{Staff.PianoPedalBracket}, the result is an @code{\override}
4455 of the specified grob type. If @var{item} is a music expression
4456 such as @qq{(} or @qq{[} the result is the same music expression
4457 with an appropriate tweak applied.
4459 The leading hyphen must be used with the @code{\tweak} form. Do
4460 not add it when @code{\alterBroken} is used as an
4463 In its @code{\override} usage, @code{\alterBroken} may be
4464 prefaced by @code{\once} or @code{\temporary} and reverted by
4465 using @code{\revert} with @var{property}.
4467 The following code applies an independent @code{\override} to
4468 each of the slur segments in the previous example:
4470 @lilypond[verbatim,quote,ragged-right]
4473 \alterBroken thickness #'(10 1) Slur
4480 The @code{\alterBroken} command may be used with any spanner
4481 object, including @code{Tie}, @code{PhrasingSlur}, @code{Beam}
4482 and @code{TextSpanner}. For example, an editor preparing a
4483 scholarly edition may wish to indicate the absence of part of a
4484 phrasing slur in a source by dashing only the segment which has
4485 been added. The following example illustrates how this can be
4486 done, in this case using the @code{\tweak} form of the command:
4488 @lilypond[verbatim,quote,ragged-right]
4489 % The empty list is conveniently used below, because it is the
4490 % default setting of dash-definition, resulting in a solid curve.
4492 c''2-\alterBroken dash-definition #'(() ((0 1.0 0.4 0.75))) \(e
4498 It is important to understand that @code{\alterBroken} will set
4499 each piece of a broken spanner to the corresponding value in
4500 @var{values}. When there are fewer values than pieces, any
4501 additional piece will be assigned the empty list. This may lead
4502 to undesired results if the layout property is not set to the
4503 empty list by default. In such cases, each segment should be
4504 assigned an appropriate value.
4507 Line breaks may occur in different places following changes in
4508 layout. Settings chosen for @code{\alterBroken} may be unsuitable
4509 for a spanner that is no longer broken or is split into more
4510 segments than before. Explicit use of @code{\break} can guard
4511 against this situation.
4513 The @code{\alterBroken} command is ineffective for spanner
4514 properties accessed before line-breaking such as
4519 @rextend{Difficult tweaks}.
4522 @node Unpure-pure containers
4523 @subsection Unpure-pure containers
4525 @cindex Scheme, pure containers
4526 @cindex Scheme, unpure containers
4527 @cindex pure containers, Scheme
4528 @cindex unpure containers, Scheme
4529 @cindex horizontal spacing, overriding
4531 Unpure-pure containers are useful for overriding @emph{Y-axis} spacing
4532 calculations - specifically @code{Y-offset} and @code{Y-extent} - with a
4533 Scheme function instead of a literal (i.e. a number or pair).
4535 For certain grobs, the @code{Y-extent} is based on the @code{stencil}
4536 property, overriding the stencil property of one of these will
4537 require an additional @code{Y-extent} override with an unpure-pure
4538 container. When a function overrides a @code{Y-offset} and/or
4539 @code{Y-extent} it is assumed that this will trigger line breaking
4540 calculations too early during compilation. So the function is not
4541 evaluated at all (usually returning a value of @samp{0} or
4542 @samp{'(0 . 0)}) which can result in collisions. A @q{pure} function
4543 will not affect properties, objects or grob suicides and therefore will
4544 always have its Y-axis-related evaluated correctly.
4546 Currently, there are about thirty functions that are already considered
4547 @q{pure} and Unpure-pure containers are a way to set functions not on
4548 this list as @q{pure}. The @q{pure} function is evaluated @emph{before}
4549 any line-breaking and so the horizontal spacing can be adjusted
4550 @q{in time}. The @q{unpure} function is then evaluated @emph{after}
4553 @warning{As it is difficult to always know which functions are on this
4554 list we recommend that any @q{pure} functions you create do not use
4555 @code{Beam} or @code{VerticalAlignment} grobs.}
4557 An unpure-pure container is constructed as follows;
4559 @code{(ly:make-unpure-pure-container f0 f1)}
4561 where @code{f0} is a function taking @var{n} arguments (@var{n >= 1})
4562 and the first argument must always be the grob. This is the function
4563 that gives the actual result. @var{f1} is the function being labeled
4564 as @q{pure} that takes @var{n + 2} arguments. Again, the first argument
4565 must always still be the grob but the second and third are @q{start}
4566 and @q{end} arguments.
4568 @var{start} and @var{end} are, for all intents and purposes, dummy
4569 values that only matter for @code{Spanners} (i.e @code{Hairpin} or
4570 @code{Beam}), that can return different height estimations based on a
4571 starting and ending column.
4573 The rest are the other arguments to the first function (which
4574 may be none if @var{n = 1}).
4576 The results of the second function are used as an approximation of the
4577 value needed which is then used by the first function to get the real
4578 value which is then used for fine-tuning much later during the spacing
4581 @lilypond[verbatim,quote,ragged-right]
4582 #(define (square-line-circle-space grob)
4583 (let* ((pitch (ly:event-property (ly:grob-property grob 'cause) 'pitch))
4584 (notename (ly:pitch-notename pitch)))
4585 (if (= 0 (modulo notename 2))
4586 (make-circle-stencil 0.5 0.0 #t)
4587 (make-filled-box-stencil '(0 . 1.0)
4590 squareLineCircleSpace = {
4591 \override NoteHead.stencil = #square-line-circle-space
4594 smartSquareLineCircleSpace = {
4595 \squareLineCircleSpace
4596 \override NoteHead.Y-extent =
4597 #(ly:make-unpure-pure-container
4598 ly:grob::stencil-height
4599 (lambda (grob start end) (ly:grob::stencil-height grob)))
4602 \new Voice \with { \remove "Stem_engraver" }
4604 \squareLineCircleSpace
4606 \smartSquareLineCircleSpace
4611 In the first measure, without the unpure-pure container, the spacing
4612 engine does not know the width of the note head and lets it collide with
4613 the accidentals. In the second measure, with unpure-pure containers,
4614 the spacing engine knows the width of the note heads and avoids the
4615 collision by lengthening the line accordingly.
4617 Usually for simple calculations nearly-identical functions for
4618 both the @q{unpure} and @q{pure} parts can be used, by only
4619 changing the number of arguments passed to, and the scope of, the
4620 function. This use case is frequent enough that
4621 @code{ly:make-unpure-pure-container} constructs such a second
4622 function by default when called with only one function argument.
4624 @warning{If a function is labeled as @q{pure} and it turns out not to
4625 be, the results can be unexpected.}
4628 @node Using music functions
4629 @section Using music functions
4631 @c TODO -- add @seealso, etc. to these subsections
4633 Where tweaks need to be reused with different music expressions,
4634 it is often convenient to make the tweak part of a @emph{music
4635 function}. In this section, we discuss only @emph{substitution}
4636 functions, where the object is to substitute a variable into a
4637 piece of LilyPond input code. Other more complex functions are
4638 described in @rextend{Music functions}.
4641 * Substitution function syntax::
4642 * Substitution function examples::
4645 @node Substitution function syntax
4646 @subsection Substitution function syntax
4648 Making a function that substitutes a variable into LilyPond
4649 code is easy. The general form of these functions is
4653 #(define-music-function
4654 (@var{arg1} @var{arg2} @dots{})
4655 (@var{type1?} @var{type2?} @dots{})
4657 @var{@dots{}music@dots{}}
4664 @multitable @columnfractions .33 .66
4665 @item @code{@var{argN}}
4666 @tab @var{n}th argument
4668 @item @code{@var{typeN?}}
4669 @tab a scheme @emph{type predicate} for which @code{@var{argN}}
4670 must return @code{#t}.
4672 @item @code{@var{@dots{}music@dots{}}}
4673 @tab normal LilyPond input, using @code{$} (in places where only
4674 Lilypond constructs are allowed) or @code{#} (to use it as a Scheme
4675 value or music function argument or music inside of music lists) to
4680 The list of type predicates is required. Some of the most common
4681 type predicates used in music functions are:
4685 cheap-list? @emph{(use instead of }@q{list?}@emph{ for faster processing)}
4697 For a list of available type predicates, see
4698 @ref{Predefined type predicates}. User-defined type predicates
4703 @ref{Predefined type predicates}.
4706 @rextend{Music functions}.
4709 @file{lily/music-scheme.cc},
4711 @file{scm/lily.scm}.
4714 @node Substitution function examples
4715 @subsection Substitution function examples
4717 This section introduces some substitution function examples.
4718 These are not intended to be exhaustive, but rather to demonstrate
4719 some of the possibilities of simple substitution functions.
4721 In the first example, a function is defined that simplifies
4722 setting the padding of a TextScript:
4724 @lilypond[quote,verbatim,ragged-right]
4726 #(define-music-function
4730 \once \override TextScript.padding = #padding
4734 c''4^"piu mosso" b a b
4736 c4^"piu mosso" b a b
4738 c4^"piu mosso" b a b
4742 In addition to numbers, we can use music expressions such
4743 as notes for arguments to music functions:
4745 @lilypond[quote,verbatim,ragged-right]
4747 #(define-music-function
4751 \tweak NoteHead.stencil #ly:text-interface::print
4752 \tweak NoteHead.text
4753 \markup \musicglyph #"custodes.mensural.u0"
4754 \tweak Stem.stencil ##f
4758 \relative { c'4 d e f \custosNote g }
4762 Both of those functions are simple single expressions where only
4763 the last element of a function call or override is missing. For
4764 those particular function definitions, there is a simpler
4765 alternative syntax, namely just writing out the constant part of
4766 the expression and replacing its final missing element with
4769 @lilypond[quote,verbatim,ragged-right]
4771 \once \override TextScript.padding = \etc
4774 c''4^"piu mosso" b a b
4776 c4^"piu mosso" b a b
4778 c4^"piu mosso" b a b
4782 @lilypond[quote,verbatim,ragged-right]
4784 \tweak NoteHead.stencil #ly:text-interface::print
4785 \tweak NoteHead.text
4786 \markup \musicglyph #"custodes.mensural.u0"
4787 \tweak Stem.stencil ##f
4790 \relative { c'4 d e f \custosNote g }
4794 Substitution functions with multiple arguments can be defined:
4796 @lilypond[quote,verbatim,ragged-right]
4798 #(define-music-function
4802 \once \override Score.MetronomeMark.padding = #padding
4803 \tempo \markup { \bold #tempotext }
4807 \tempo \markup { "Low tempo" }
4809 \tempoPadded #4.0 "High tempo"
4814 @c TODO: add appropriate @@ref's here.