1 @c -*- coding: utf-8; mode: texinfo; -*-
2 @node Changing defaults
3 @chapter Changing defaults
6 The purpose of LilyPond's design is to provide the finest output
7 quality as a default. Nevertheless, it may happen that you need to
8 change this default layout. The layout is controlled through a large
9 number of proverbial @q{knobs and switches.} This chapter does not
10 list each and every knob. Rather, it outlines what groups of controls
11 are available and explains how to lookup which knob to use for a
15 @cindex Program reference
17 The controls available for tuning are described in a separate
20 Program reference manual.
23 @ref{Top,Program reference,,lilypond-internals}.
26 lists all different variables, functions and options available in
27 LilyPond. It is written as a HTML document, which is available
28 @uref{http://@/lilypond@/.org/@/doc/@/v2.8/@/Documentation/@/user/@/
29 lilypond@/-internals/,on@/-line},
30 but is also included with the LilyPond documentation package.
32 There are four areas where the default settings may be changed:
36 Automatic notation: changing the automatic creation of notation
37 elements. For example, changing the beaming rules.
40 Output: changing the appearance of individual
41 objects. For example, changing stem directions or the location of
45 Context: changing aspects of the translation from music events to
46 notation. For example, giving each staff a separate time signature.
49 Page layout: changing the appearance of the spacing, line
50 breaks, and page dimensions. These modifications are discussed
51 in @ref{Non-musical notation} and @ref{Spacing issues}.
54 Internally, LilyPond uses Scheme (a LISP dialect) to provide
55 infrastructure. Overriding layout decisions in effect accesses the
56 program internals, which requires Scheme input. Scheme elements are
57 introduced in a @code{.ly} file with the hash mark
58 @code{#}.@footnote{@ref{Scheme tutorial} contains a short tutorial
59 on entering numbers, lists, strings, and symbols in Scheme.}
63 * Automatic notation::
64 * Interpretation contexts::
65 * The \override command::
69 @node Automatic notation
70 @section Automatic notation
72 This section describes how to change the way that accidentals and
73 beams are automatically displayed.
76 * Automatic accidentals::
77 * Setting automatic beam behavior::
80 @node Automatic accidentals
81 @subsection Automatic accidentals
82 @cindex Automatic accidentals
84 Common rules for typesetting accidentals have been placed in a
85 function. This function is called as follows
87 @funindex set-accidental-style
89 #(set-accidental-style 'STYLE #('CONTEXT#))
92 The function can take two arguments: the name of the accidental style,
93 and an optional argument that denotes the context that should be
94 changed. If no context name is supplied, @code{Staff} is the default,
95 but you may wish to apply the accidental style to a single @code{Voice}
98 @c TODO: we should create a very clear example, and show every
99 @c accidental style on that example (with the example specially
100 @c constructed so that it illustrates all the differences). -gp
102 The following accidental styles are supported
105 This is the default typesetting behavior. It corresponds
106 to 18th century common practice: Accidentals are
107 remembered to the end of the measure in which they occur and
108 only on their own octave.
111 The normal behavior is to remember the accidentals on
112 Staff-level. This variable, however, typesets accidentals
113 individually for each voice. Apart from that, the rule is similar to
116 As a result, accidentals from one voice do not get canceled in other
117 voices, which is often an unwanted result
119 @lilypond[quote,ragged-right,relative=1,fragment,verbatim]
121 #(set-accidental-style 'voice)
128 The @code{voice} option should be used if the voices
129 are to be read solely by individual musicians. If the staff is to be
130 used by one musician (e.g., a conductor) then
131 @code{modern} or @code{modern-cautionary}
132 should be used instead.
135 @funindex modern style accidentals
136 This rule corresponds to the common practice in the 20th century. This rule
137 prints the same accidentals as @code{default}, but temporary
138 accidentals also are canceled in other octaves. Furthermore,
139 in the same octave, they also get canceled in the following
142 @lilypond[quote,ragged-right,fragment,verbatim]
143 #(set-accidental-style 'modern)
144 cis' c'' cis'2 | c'' c'
147 @item @code{modern-cautionary}
148 @funindex modern-cautionary
149 This rule is similar to @code{modern}, but the @q{extra} accidentals
150 (the ones not typeset by @code{default}) are typeset as cautionary
151 accidentals. They are printed in reduced size or with parentheses
152 @lilypond[quote,ragged-right,fragment,verbatim]
153 #(set-accidental-style 'modern-cautionary)
154 cis' c'' cis'2 | c'' c'
157 @funindex modern-voice
159 This rule is used for multivoice accidentals to be read both by musicians
160 playing one voice and musicians playing all voices. Accidentals are
161 typeset for each voice, but they @emph{are} canceled across voices in
162 the same @internalsref{Staff}.
164 @funindex modern-voice-cautionary
165 @item modern-voice-cautionary
166 This rule is the same as @code{modern-voice}, but with the extra
167 accidentals (the ones not typeset by @code{voice}) typeset
168 as cautionaries. Even though all accidentals typeset by
169 @code{default} @emph{are} typeset by this variable,
170 some of them are typeset as cautionaries.
173 @funindex piano accidentals
174 This rule reflects 20th century practice for piano notation. Very similar to
175 @code{modern} but accidentals also get canceled
176 across the staves in the same @internalsref{GrandStaff} or
177 @internalsref{PianoStaff}.
179 @item piano-cautionary
180 @funindex #(set-accidental-style 'piano-cautionary)
181 Same as @code{#(set-accidental-style 'piano)} but with the extra
182 accidentals typeset as cautionaries.
185 @funindex no-reset accidental style
186 This is the same as @code{default} but with accidentals lasting
187 @q{forever} and not only until the next measure
188 @lilypond[quote,ragged-right,fragment,verbatim,relative=1]
189 #(set-accidental-style 'no-reset)
194 This is sort of the opposite of @code{no-reset}: Accidentals
195 are not remembered at all -- and hence all accidentals are
196 typeset relative to the key signature, regardless of what was
199 @lilypond[quote,ragged-right,fragment,verbatim,relative=1]
200 #(set-accidental-style 'forget)
201 \key d\major c4 c cis cis d d dis dis
208 Program reference: @internalsref{Accidental_engraver},
209 @internalsref{Accidental}, and @internalsref{AccidentalPlacement}.
214 Simultaneous notes are considered to be entered in sequential
215 mode. This means that in a chord the accidentals are typeset as if the
216 notes in the chord happen one at a time, in the order in which
217 they appear in the input file. This is a problem when accidentals
218 in a chord depend on each other,
219 which does not happen for the default accidental style. The problem
220 can be solved by manually inserting @code{!} and @code{?} for the
224 @node Setting automatic beam behavior
225 @subsection Setting automatic beam behavior
227 @funindex autoBeamSettings
228 @funindex (end * * * *)
229 @funindex (begin * * * *)
230 @cindex automatic beams, tuning
231 @cindex tuning automatic beaming
233 @c [TODO: use \applyContext]
235 In normal time signatures, automatic beams can start on any note but can
236 only end in a few positions within the measure: beams can end on a beat,
237 or at durations specified by the properties in
238 @code{autoBeamSettings}. The properties in @code{autoBeamSettings}
239 consist of a list of rules for where beams can begin and end. The
240 default @code{autoBeamSettings} rules are defined in
241 @file{scm/@/auto@/-beam@/.scm}.
243 In order to add a rule to the list, use
245 #(override-auto-beam-setting '(be p q n m) a b [context])
250 @item @code{be} is either "begin" or "end".
252 @item @code{p/q} is the duration of the note for which you want
253 to add a rule. A beam is considered to have the duration of its
254 shortest note. Set @code{p} and @code{q} to @code{'*'} to
255 have this apply to any beam.
257 @item @code{n/m} is the time signature to which
258 this rule should apply. Set @code{n} and @code{m} to @code{'*'}
259 to have this apply in any time signature.
261 @item @code{a/b} is the position in the bar at which the beam should
264 @item @code{context} is optional, and it specifies the context at which
265 the change should be made. The default is @code{'Voice}.
266 @code{#(score-override-auto-beam-setting '(A B C D) E F)} is equivalent to
267 @code{#(override-auto-beam-setting '(A B C D) E F 'Score)}.
271 For example, if automatic beams should always end on the first quarter
275 #(override-auto-beam-setting '(end * * * *) 1 4)
278 You can force the beam settings to only take effect on beams whose shortest
279 note is a certain duration
281 @lilypond[quote,fragment,ragged-right,verbatim,relative=2]
283 #(override-auto-beam-setting '(end 1 16 * *) 1 16)
285 a32 a a a a16 a a a a a |
286 #(override-auto-beam-setting '(end 1 32 * *) 1 16)
287 a32 a a a a16 a a a a a |
290 You can force the beam settings to only take effect in certain time
293 @lilypond[quote,fragment,ragged-right,verbatim,relative=2]
295 #(override-auto-beam-setting '(end * * 5 8) 2 8)
303 You can also remove a previously set beam-ending rule by using
306 #(revert-auto-beam-setting '(be p q n m) a b [context])
310 be, p, q, n, m, a, b and context are the same as above. Note that the
311 default rules are specified in @file{scm/@/auto@/-beam@/.scm},
312 so you can revert rules that you did not explicitly create.
314 @lilypond[quote,fragment,ragged-right,verbatim,relative=2]
316 a16 a a a a a a a a a a a a a a a
317 #(revert-auto-beam-setting '(end 1 16 4 4) 1 4)
318 a16 a a a a a a a a a a a a a a a
321 The rule in a revert-auto-beam-setting statement must exactly match the
322 original rule. That is, no wildcard expansion is taken into account.
324 @lilypond[quote,fragment,ragged-right,verbatim,relative=2]
326 #(override-auto-beam-setting '(end 1 16 1 4) 1 8)
328 #(revert-auto-beam-setting '(end 1 16 * *) 1 8) % this won't revert it!
330 #(revert-auto-beam-setting '(end 1 16 1 4) 1 8) % this will
336 @c TODO: old material -- not covered by above stuff, I think.
337 If automatic beams should end on every quarter in 5/4 time, specify
340 #(override-auto-beam-setting '(end * * * *) 1 4 'Staff)
341 #(override-auto-beam-setting '(end * * * *) 1 2 'Staff)
342 #(override-auto-beam-setting '(end * * * *) 3 4 'Staff)
343 #(override-auto-beam-setting '(end * * * *) 5 4 'Staff)
347 The same syntax can be used to specify beam starting points. In this
348 example, automatic beams can only end on a dotted quarter note
350 #(override-auto-beam-setting '(end * * * *) 3 8)
351 #(override-auto-beam-setting '(end * * * *) 1 2)
352 #(override-auto-beam-setting '(end * * * *) 7 8)
354 In 4/4 time signature, this means that automatic beams could end only on
355 3/8 and on the fourth beat of the measure (after 3/4, that is 2 times
356 3/8, has passed within the measure).
358 If any unexpected beam behaviour occurs, check the default automatic beam
359 settings in @file{scm/@/auto@/-beam@/.scm}
360 for possible interference, because the beam
361 endings defined there will still apply on top of your own overrides. Any
362 unwanted endings in the default vales must be reverted for your time
365 For example, to typeset @code{(3 4 3 2)}-beam endings in 12/8, begin
369 %%% revert default values in scm/auto-beam.scm regarding 12/8 time
370 #(revert-auto-beam-setting '(end * * 12 8) 3 8)
371 #(revert-auto-beam-setting '(end * * 12 8) 3 4)
372 #(revert-auto-beam-setting '(end * * 12 8) 9 8)
375 #(override-auto-beam-setting '(end 1 8 12 8) 3 8)
376 #(override-auto-beam-setting '(end 1 8 12 8) 7 8)
377 #(override-auto-beam-setting '(end 1 8 12 8) 10 8)
380 @cindex automatic beam generation
382 @funindex autoBeaming
385 If beams are used to indicate melismata in songs, then automatic
386 beaming should be switched off with @code{\autoBeamOff}.
391 @funindex \autoBeamOff
393 @funindex \autoBeamOn
398 Beaming patterns may be altered with the @code{beatGrouping} property,
400 @lilypond[quote,verbatim,relative=2,fragment,ragged-right]
402 \set beatGrouping = #'(2 3)
404 \set beatGrouping = #'(3 2)
411 If a score ends while an automatic beam has not been ended and is
412 still accepting notes, this last beam will not be typeset at all. The
413 same holds polyphonic voices, entered with @code{<< @dots{} \\ @dots{}
414 >>}. If a polyphonic voice ends while an automatic beam is still
415 accepting notes, it is not typeset.
418 @node Interpretation contexts
419 @section Interpretation contexts
421 This section describes what contexts are, and how to modify them.
424 * Contexts explained::
425 * Creating contexts::
426 * Changing context properties on the fly::
427 * Modifying context plug-ins::
428 * Layout tunings within contexts::
429 * Changing context default settings::
430 * Defining new contexts::
431 * Aligning contexts::
435 @node Contexts explained
436 @subsection Contexts explained
438 When music is printed, a lot of notational elements must be added to the
439 input. For example, compare the input and output of the following example:
441 @lilypond[quote,verbatim,relative=2,fragment]
445 The input is rather sparse, but in the output, bar lines, accidentals,
446 clef, and time signature are added. LilyPond @emph{interprets} the
447 input. During this step, the musical information is inspected in time
448 order, similar to reading a score from left to right. While reading
449 the input, the program remembers where measure boundaries are, and which
450 pitches require explicit accidentals. This information can be presented on
451 several levels. For example, the effect of an accidental is limited
452 to a single staff, while a bar line must be synchronized across the
455 Within LilyPond, these rules and bits of information are grouped in
456 @emph{Contexts}. Some examples of contexts are @context{Voice},
457 @context{Staff}, and @context{Score}. They are hierarchical, for
458 example: a @context{Staff} can contain many @context{Voice}s, and a
459 @context{Score} can contain many @context{Staff} contexts.
462 @image{context-example,5cm,,}
465 Each context has the responsibility for enforcing some notation rules,
466 creating some notation objects and maintaining the associated
467 properties. For example, the @context{Voice} context may introduce an
468 accidental and then the @context{Staff} context maintains the rule to
469 show or suppress the accidental for the remainder of the measure. The
470 synchronization of bar lines is handled at @context{Score} context.
472 However, in some music we may not want the bar lines to be
473 synchronized -- consider a polymetric score in 4/4 and 3/4 time. In
474 such cases, we must modify the default settings of the @context{Score}
475 and @context{Staff} contexts.
477 For very simple scores, contexts are created implicitly, and you need
478 not be aware of them. For larger pieces, such as anything with more
479 than one staff, they must be
480 created explicitly to make sure that you get as many staves as you
481 need, and that they are in the correct order. For typesetting pieces
482 with specialized notation, it can be useful to modify existing or
483 to define new contexts.
486 A complete description of all available contexts is in the program
489 @internalsref{Contexts}.
492 Translation @arrow{} Context.
495 @c [TODO: describe propagation]
498 @node Creating contexts
499 @subsection Creating contexts
501 For scores with only one voice and one staff, contexts are
502 created automatically. For more complex scores, it is necessary to
503 create them by hand. There are three commands that do this.
508 The easiest command is @code{\new}, and it also the quickest to type.
509 It is prepended to a music expression, for example
513 @cindex Context, creating
516 \new @var{type} @var{music expression}
520 where @var{type} is a context name (like @code{Staff} or
521 @code{Voice}). This command creates a new context, and starts
522 interpreting the @var{music expression} with that.
524 A practical application of @code{\new} is a score with many
525 staves. Each part that should be on its own staff, is preceded with
528 @lilypond[quote,verbatim,relative=2,ragged-right,fragment]
535 The @code{\new} command may also give a name to the context,
538 \new @var{type} = @var{id} @var{music}
540 However, this user specified name is only used if there is no other
541 context already earlier with the same name.
547 Like @code{\new}, the @code{\context} command also directs a music
548 expression to a context object, but gives the context an explicit name. The
552 \context @var{type} = @var{id} @var{music}
555 This form will search for an existing context of type @var{type}
556 called @var{id}. If that context does not exist yet, a new
557 context with the specified name is created. This is useful if
558 the context is referred to later on. For example, when
559 setting lyrics the melody is in a named context
562 \context Voice = "@b{tenor}" @var{music}
566 so the texts can be properly aligned to its notes,
569 \new Lyrics \lyricsto "@b{tenor}" @var{lyrics}
574 Another possible use of named contexts is funneling two different
575 music expressions into one context. In the following example,
576 articulations and notes are entered separately,
580 arts = @{ s4-. s4-> @}
583 They are combined by sending both to the same @context{Voice} context,
587 \new Staff \context Voice = "A" \music
588 \context Voice = "A" \arts
591 @lilypond[quote,ragged-right]
595 \new Staff \context Voice = "A" \music
596 \context Voice = "A" \arts
600 With this mechanism, it is possible to define an Urtext (original
601 edition), with the option to put several distinct articulations on the
604 @cindex creating contexts
607 The third command for creating contexts is
609 \context @var{type} @var{music}
614 This is similar to @code{\context} with @code{= @var{id}}, but matches
615 any context of type @var{type}, regardless of its given name.
617 This variant is used with music expressions that can be interpreted at
618 several levels. For example, the @code{\applyOutput} command (see
619 @ref{Running a function on all layout objects}). Without an explicit
620 @code{\context}, it is usually applied to @context{Voice}
623 \applyOutput #'@var{context} #@var{function} % apply to Voice
626 To have it interpreted at the @context{Score} or @context{Staff} level use
630 \applyOutput #'Score #@var{function}
631 \applyOutput #'Staff #@var{function}
637 @node Changing context properties on the fly
638 @subsection Changing context properties on the fly
642 @cindex changing properties
644 Each context can have different @emph{properties}, variables contained
645 in that context. They can be changed during the interpretation step.
646 This is achieved by inserting the @code{\set} command in the music,
649 \set @var{context}.@var{prop} = #@var{value}
653 @lilypond[quote,verbatim,relative=2,fragment]
655 \set Score.skipBars = ##t
659 This command skips measures that have no notes. The result is that
660 multi-rests are condensed. The value assigned is a Scheme object. In
661 this case, it is @code{#t}, the boolean True value.
663 If the @var{context} argument is left out, then the current bottom-most
664 context (typically @context{ChordNames}, @context{Voice}, or
665 @context{Lyrics}) is used. In this example,
667 @lilypond[quote,verbatim,relative=2,fragment]
669 \set autoBeaming = ##f
674 the @var{context} argument to @code{\set} is left out, so automatic
675 beaming is switched off in the current @internalsref{Voice}. Note that
676 the bottom-most context does not always contain the property that you
677 wish to change -- for example, attempting to set the @code{skipBars}
678 property (of the bottom-most context, in this case @code{Voice}) will
681 @lilypond[quote,verbatim,relative=2,fragment]
687 Contexts are hierarchical, so if a bigger context was specified, for
688 example @context{Staff}, then the change would also apply to all
689 @context{Voice}s in the current stave. The change is applied
690 @q{on-the-fly}, during the music, so that the setting only affects the
691 second group of eighth notes.
695 There is also an @code{\unset} command,
697 \unset @var{context}.@var{prop}
701 which removes the definition of @var{prop}. This command removes
702 the definition only if it is set in @var{context}, so
705 \set Staff.autoBeaming = ##f
709 introduces a property setting at @code{Staff} level. The setting also
710 applies to the current @code{Voice}. However,
713 \unset Voice.autoBeaming
717 does not have any effect. To cancel this setting, the @code{\unset}
718 must be specified on the same level as the original @code{\set}. In
719 other words, undoing the effect of @code{Staff.autoBeaming = ##f}
722 \unset Staff.autoBeaming
725 Like @code{\set}, the @var{context} argument does not have to be
726 specified for a bottom context, so the two statements
729 \set Voice.autoBeaming = ##t
730 \set autoBeaming = ##t
738 Settings that should only apply to a single time-step can be entered
739 with @code{\once}, for example in
741 @lilypond[quote,verbatim,relative=2,fragment]
743 \once \set fontSize = #4.7
748 the property @code{fontSize} is unset automatically after the second
751 A full description of all available context properties is in the
752 program reference, see
754 @internalsref{Tunable context properties}.
757 Translation @arrow{} Tunable context properties.
761 @node Modifying context plug-ins
762 @subsection Modifying context plug-ins
764 Notation contexts (like @code{Score} and @code{Staff}) not only
766 they also contain plug-ins called @q{engravers} that create notation
767 elements. For example, the @code{Voice} context contains a
768 @code{Note_head_engraver} and the @code{Staff} context contains a
769 @code{Key_signature_engraver}.
771 For a full a description of each plug-in, see
773 @internalsref{Engravers}.
776 Program reference @arrow Translation @arrow{} Engravers.
778 Every context described in
780 @internalsref{Contexts}
783 Program reference @arrow Translation @arrow{} Context.
785 lists the engravers used for that context.
788 It can be useful to shuffle around these plug-ins. This is done by
789 starting a new context with @code{\new} or @code{\context}, and
795 \new @var{context} \with @{
808 where the @dots{} should be the name of an engraver. Here is a simple
809 example which removes @code{Time_signature_engraver} and
810 @code{Clef_engraver} from a @code{Staff} context,
812 @lilypond[quote,relative=1,verbatim,fragment]
818 \remove "Time_signature_engraver"
819 \remove "Clef_engraver"
826 In the second staff there are no time signature or clef symbols. This
827 is a rather crude method of making objects disappear since it will affect
828 the entire staff. This method also influences the spacing, which may or
829 may not be desirable. A more
830 sophisticated method of blanking objects is shown in @ref{Common tweaks}.
832 The next example shows a practical application. Bar lines and time
833 signatures are normally synchronized across the score. This is done
834 by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
835 This plug-in keeps an administration of time signature, location
836 within the measure, etc. By moving thes engraver from @code{Score} to
837 @code{Staff} context, we can have a score where each staff has its own
840 @cindex polymetric scores
841 @cindex Time signatures, multiple
843 @lilypond[quote,relative=1,ragged-right,verbatim,fragment]
845 \remove "Timing_translator"
846 \remove "Default_bar_line_engraver"
849 \consists "Timing_translator"
850 \consists "Default_bar_line_engraver"
856 \consists "Timing_translator"
857 \consists "Default_bar_line_engraver"
866 @node Layout tunings within contexts
867 @subsection Layout tunings within contexts
869 Each context is responsible for creating certain types of graphical
870 objects. The settings used for printing these objects are also stored by
871 context. By changing these settings, the appearance of objects can be
874 The syntax for this is
877 \override @var{context}.@var{name} #'@var{property} = #@var{value}
880 Here @var{name} is the name of a graphical object, like @code{Stem} or
881 @code{NoteHead}, and @var{property} is an internal variable of the
882 formatting system (@q{grob property} or @q{layout property}). The latter is a
883 symbol, so it must be quoted. The subsection @ref{Constructing a
884 tweak} explains what to fill in for @var{name}, @var{property}, and
885 @var{value}. Here we only discuss the functionality of this command.
890 \override Staff.Stem #'thickness = #4.0
894 makes stems thicker (the default is 1.3, with staff line thickness as a
895 unit). Since the command specifies @context{Staff} as context, it only
896 applies to the current staff. Other staves will keep their normal
897 appearance. Here we see the command in action:
899 @lilypond[quote,verbatim,relative=2,fragment]
901 \override Staff.Stem #'thickness = #4.0
907 The @code{\override} command changes the definition of the @code{Stem}
908 within the current @context{Staff}. After the command is interpreted
909 all stems are thickened.
911 Analogous to @code{\set}, the @var{context} argument may be left out,
912 causing it to default to @context{Voice}, and adding @code{\once} applies
913 the change during one timestep only
915 @lilypond[quote,fragment,verbatim,relative=2]
917 \once \override Stem #'thickness = #4.0
922 The @code{\override} must be done before the object is
923 started. Therefore, when altering @emph{Spanner} objects such as slurs
924 or beams, the @code{\override} command must be executed at the moment
925 when the object is created. In this example,
927 @lilypond[quote,fragment,verbatim,relative=2]
928 \override Slur #'thickness = #3.0
930 \override Beam #'thickness = #0.6
935 the slur is fatter but the beam is not. This is because the command for
936 @code{Beam} comes after the Beam is started, so it has no effect.
938 Analogous to @code{\unset}, the @code{\revert} command for a context
939 undoes an @code{\override} command; like with @code{\unset}, it only
940 affects settings that were made in the same context. In other words, the
941 @code{\revert} in the next example does not do anything.
944 \override Voice.Stem #'thickness = #4.0
945 \revert Staff.Stem #'thickness
948 Some tweakable options are called @q{subproperties} and reside inside
949 properties. To tweak those, use commands of the form
951 @c leave this as a long long
953 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
960 \override Stem #'details #'beamed-lengths = #'(4 4 3)
966 Internals: @internalsref{OverrideProperty}, @internalsref{RevertProperty},
967 @internalsref{PropertySet}, @internalsref{Backend}, and
968 @internalsref{All layout objects}.
973 The back-end is not very strict in type-checking object properties.
974 Cyclic references in Scheme values for properties can cause hangs
978 @node Changing context default settings
979 @subsection Changing context default settings
981 The adjustments of the previous subsections (@ref{Changing context
982 properties on the fly}, @ref{Modifying context plug-ins}, and
983 @ref{Layout tunings within contexts}) can also be entered separately
984 from the music in the @code{\layout} block,
993 \override Stem #'thickness = #4.0
994 \remove "Time_signature_engraver"
999 Here @code{\Staff} takes the existing definition for context @context{Staff} from the
1000 identifier @code{\Staff}.
1005 \override Stem #'thickness = #4.0
1006 \remove "Time_signature_engraver"
1010 affect all staves in the score. Other contexts can be modified
1013 The @code{\set} keyword is optional within the @code{\layout} block, so
1029 It is not possible to collect context changes in a variable and apply
1030 them to a @code{\context} definition by referring to that variable.
1032 The @code{\RemoveEmptyStaffContext} will overwrite your current
1033 @code{\Staff} settings. If you wish to change the defaults for a
1034 staff which uses @code{\RemoveEmptyStaffContext}, you must do so
1035 after calling @code{\RemoveemptyStaffContext}, ie
1040 \RemoveEmptyStaffContext
1042 \override Stem #'thickness = #4.0
1048 @node Defining new contexts
1049 @subsection Defining new contexts
1051 Specific contexts, like @context{Staff} and @code{Voice}, are made of
1052 simple building blocks. It is possible to create new types of
1053 contexts with different combinations of engraver plug-ins.
1055 The next example shows how to build a different type of
1056 @context{Voice} context from scratch. It will be similar to
1057 @code{Voice}, but only prints centered slash noteheads. It can be used
1058 to indicate improvisation in jazz pieces,
1060 @lilypond[quote,ragged-right]
1061 \layout { \context {
1063 \type "Engraver_group"
1064 \consists "Note_heads_engraver"
1065 \consists "Text_engraver"
1066 \consists Pitch_squash_engraver
1067 squashedPosition = #0
1068 \override NoteHead #'style = #'slash
1069 \override Stem #'transparent = ##t
1073 \accepts "ImproVoice"
1077 a4 d8 bes8 \new ImproVoice { c4^"ad lib" c
1078 c4 c^"undress" c_"while playing :)" c }
1084 These settings are defined within a @code{\context} block inside a
1085 @code{\layout} block,
1095 In the following discussion, the example input shown should go on the
1096 @dots{} in the previous fragment.
1098 First the context's name is defined. Instead of @context{Voice} it
1099 will be called @context{ImproVoice},
1105 Since it is similar to the @context{Voice}, we want commands that work
1106 on (existing) @context{Voice}s to remain working. This is achieved by
1107 giving the new context an alias @context{Voice},
1113 The context will print notes, and instructive texts
1116 \consists Note_heads_engraver
1117 \consists Text_engraver
1120 but only on the center line,
1123 \consists Pitch_squash_engraver
1124 squashedPosition = #0
1127 The @internalsref{Pitch_squash_engraver} modifies note heads (created
1128 by @internalsref{Note_heads_engraver}) and sets their vertical
1129 position to the value of @code{squashedPosition}, in this case@tie{}@code{0},
1132 The notes look like a slash, and have no stem,
1135 \override NoteHead #'style = #'slash
1136 \override Stem #'transparent = ##t
1139 All these plug-ins have to cooperate, and this is achieved with a
1140 special plug-in, which must be marked with the keyword @code{\type}.
1141 This should always be @internalsref{Engraver_group},
1144 \type "Engraver_group"
1147 Put together, we get
1152 \type "Engraver_group"
1153 \consists "Note_heads_engraver"
1154 \consists "Text_engraver"
1155 \consists Pitch_squash_engraver
1156 squashedPosition = #0
1157 \override NoteHead #'style = #'slash
1158 \override Stem #'transparent = ##t
1164 Contexts form hierarchies. We want to hang the @context{ImproVoice}
1165 under @context{Staff}, just like normal @code{Voice}s. Therefore, we
1166 modify the @code{Staff} definition with the @code{\accepts}
1177 The opposite of @code{\accepts} is @code{\denies},
1178 which is sometimes needed when reusing existing context definitions.
1180 Putting both into a @code{\layout} block, like
1190 \accepts "ImproVoice"
1195 Then the output at the start of this subsection can be entered as
1203 c c_"while playing :)"
1210 @node Aligning contexts
1211 @subsection Aligning contexts
1213 New contexts may be aligned above or below exisiting contexts. This
1214 could be useful in setting up a vocal staff (@ref{Vocal ensembles}) and
1218 @findex alignAboveContext
1219 @findex alignBelowContext
1221 @lilypond[quote,ragged-right]
1222 ossia = { f4 f f f }
1224 \relative c' \new Staff = "main" {
1227 \new Staff \with {alignAboveContext=main} \ossia
1228 { d8 f d f d f d f }
1236 @node The \override command
1237 @section The \override command
1239 In the previous section, we have already touched on a command that
1240 changes layout details: the @code{\override} command. In this section,
1241 we will look in more detail at how to use the command in practice.
1245 * Constructing a tweak::
1246 * Navigating the program reference::
1247 * Layout interfaces::
1248 * Determining the grob property::
1249 * Objects connected to the input::
1250 * \set vs. \override::
1251 * Difficult tweaks::
1256 @node Constructing a tweak
1257 @subsection Constructing a tweak
1259 Commands which change output generally look like
1262 \override Voice.Stem #'thickness = #3.0
1266 This means that we must determine these bits of information:
1269 @item the context: here @context{Voice}.
1270 @item the layout object: here @code{Stem}.
1271 @item the layout property: here @code{thickness}.
1272 @item a sensible value: here @code{3.0}.
1275 Some tweakable options are called @q{subproperties} and reside inside
1276 properties. To tweak those, use commands in the form
1279 \override Stem #'details #'beamed-lengths = #'(4 4 3)
1282 @cindex internal documentation
1283 @cindex finding graphical objects
1284 @cindex graphical object descriptions
1287 @cindex internal documentation
1289 We demonstrate how to glean this information from the notation manual
1290 and the program reference.
1293 @node Navigating the program reference
1294 @subsection Navigating the program reference
1296 Suppose we want to move the fingering indication in the fragment
1299 @lilypond[quote,fragment,relative=2,verbatim]
1305 If you visit the documentation on fingering instructions (in
1306 @ref{Fingering instructions}), you will notice:
1311 Program reference: @internalsref{Fingering}.
1316 @c outdated info; probably will delete.
1318 This fragment points to two parts of the program reference: a page
1319 on @code{FingerEvent} and one on @code{Fingering}.
1321 The page on @code{FingerEvent} describes the properties of the music
1322 expression for the input @code{-2}. The page contains many links
1323 forward. For example, it says
1326 Accepted by: @internalsref{Fingering_engraver},
1330 That link brings us to the documentation for the Engraver, the
1334 This engraver creates the following layout objects: @internalsref{Fingering}.
1337 In other words, once the @code{FingerEvent}s are interpreted, the
1338 @code{Fingering_engraver} plug-in will process them.
1342 @c I can't figure out what this is supposed to mean. -gp
1344 The @code{Fingering_engraver} is also listed to create
1345 @internalsref{Fingering} objects,
1347 @c old info? it doesn't make any sense to me with our current docs.
1349 second bit of information listed under @b{See also} in the Notation
1353 Follow the link to @internalsref{Fingering}. At the top of the
1357 Fingering objects are created by: @internalsref{Fingering_engraver} and
1358 @internalsref{New_fingering_engraver}.
1361 By clicking around in the program reference, we can follow the
1362 flow of information within the program, following links like this:
1366 @item @internalsref{Fingering}:
1367 @internalsref{Fingering} objects are created by:
1368 @internalsref{Fingering_engraver}
1370 @item @internalsref{Fingering_engraver}:
1371 Music types accepted: @internalsref{fingering-event}
1373 @item @internalsref{fingering-event}:
1374 Music event type @code{fingering-event} is in Music expressions named
1375 @internalsref{FingerEvent}
1378 This path goes against the flow of information in the program: it
1379 starts from the output, and ends at the input event. You could
1380 also start at an input event, and read with the flow of
1381 information, eventually ending up at the output object(s).
1383 The program reference can also be browsed like a normal document. It
1384 contains chapters on
1386 @internalsref{Music definitions},
1389 @code{Music definitions}
1391 on @internalsref{Translation}, and the @internalsref{Backend}. Every
1392 chapter lists all the definitions used and all properties that may be
1396 @node Layout interfaces
1397 @subsection Layout interfaces
1399 @cindex interface, layout
1400 @cindex layout interface
1403 The HTML page that we found in the previous section describes the
1404 layout object called @internalsref{Fingering}. Such an object is a
1405 symbol within the score. It has properties that store numbers (like
1406 thicknesses and directions), but also pointers to related objects. A
1407 layout object is also called a @emph{Grob}, which is short for Graphical
1408 Object. For more details about Grobs, see @internalsref{grob-interface}.
1410 The page for @code{Fingering} lists the definitions for the
1411 @code{Fingering} object. For example, the page says
1414 @code{padding} (dimension, in staff space):
1420 which means that the number will be kept at a distance of at least 0.6
1424 Each layout object may have several functions as a notational or
1425 typographical element. For example, the Fingering object
1426 has the following aspects
1430 Its size is independent of the horizontal spacing, unlike slurs or beams.
1433 It is a piece of text. Granted, it is usually a very short text.
1436 That piece of text is typeset with a font, unlike slurs or beams.
1439 Horizontally, the center of the symbol should be aligned to the
1440 center of the notehead.
1443 Vertically, the symbol is placed next to the note and the staff.
1446 The vertical position is also coordinated with other superscript
1447 and subscript symbols.
1450 Each of these aspects is captured in so-called @emph{interface}s,
1451 which are listed on the @internalsref{Fingering} page at the bottom
1454 This object supports the following interfaces:
1455 @internalsref{item-interface},
1456 @internalsref{self-alignment-interface},
1457 @internalsref{side-position-interface}, @internalsref{text-interface},
1458 @internalsref{text-script-interface}, @internalsref{font-interface},
1459 @internalsref{finger-interface}, and @internalsref{grob-interface}.
1462 Clicking any of the links will take you to the page of the respective
1463 object interface. Each interface has a number of properties. Some of
1464 them are not user-serviceable (@q{Internal properties}), but others
1467 We have been talking of @emph{the} @code{Fingering} object, but actually it
1468 does not amount to much. The initialization file (see
1469 @ref{Default files})
1470 @file{scm/@/define@/-grobs@/.scm} shows the soul of the @q{object},
1475 (avoid-slur . around)
1476 (slur-padding . 0.2)
1477 (staff-padding . 0.5)
1478 (self-alignment-X . 0)
1479 (self-alignment-Y . 0)
1480 (script-priority . 100)
1481 (stencil . ,ly:text-interface::print)
1482 (direction . ,ly:script-interface::calc-direction)
1483 (font-encoding . fetaNumber)
1484 (font-size . -5) ; don't overlap when next to heads.
1485 (meta . ((class . Item)
1486 (interfaces . (finger-interface
1488 text-script-interface
1490 side-position-interface
1491 self-alignment-interface
1492 item-interface))))))
1496 As you can see, the @code{Fingering} object is nothing more than a
1497 bunch of variable settings, and the webpage in the Program Reference
1498 is directly generated from this definition.
1501 @node Determining the grob property
1502 @subsection Determining the grob property
1504 Recall that we wanted to change the position of the @b{2} in
1506 @lilypond[quote,fragment,relative=2,verbatim]
1512 Since the @b{2} is vertically positioned next to its note, we have to
1513 meddle with the interface associated with this positioning. This is
1514 done using @code{side-position-interface}. The page for this interface
1518 @code{side-position-interface}
1520 Position a victim object (this one) next to other objects (the
1521 support). The property @code{direction} signifies where to put the
1522 victim object relative to the support (left or right, up or down?)
1527 Below this description, the variable @code{padding} is described as
1532 (dimension, in staff space)
1534 Add this much extra space between objects that are next to each other.
1538 By increasing the value of @code{padding}, we can move the
1539 fingering away from the notehead. The following command inserts
1540 3 staff spaces of white
1541 between the note and the fingering:
1543 \once \override Voice.Fingering #'padding = #3
1546 Inserting this command before the Fingering object is created,
1547 i.e., before @code{c2}, yields the following result:
1549 @lilypond[quote,relative=2,fragment,verbatim]
1550 \once \override Voice.Fingering #'padding = #3
1557 In this case, the context for this tweak is @context{Voice}. This
1558 fact can also be deduced from the program reference, for the page for
1559 the @internalsref{Fingering_engraver} plug-in says
1562 Fingering_engraver is part of contexts: @dots{} @internalsref{Voice}
1566 @node Objects connected to the input
1567 @subsection Objects connected to the input
1571 In some cases, it is possible to take a short-cut for tuning graphical
1572 objects. For objects that result directly from a piece of the input,
1573 you can use the @code{\tweak} function, for example
1575 @lilypond[relative=2,fragment,verbatim,ragged-right]
1578 \tweak #'color #red d
1580 \tweak #'duration-log #1 a
1581 >4-\tweak #'padding #10 -.
1584 As you can see, properties are set directly in the objects directly,
1585 without mentioning the grob name or context where this should be
1588 This technique only works for objects that are directly connected to
1589 an @internalsref{event} from the input, for example
1592 @item note heads, caused by chord-pitch (i.e., notes inside a chord).
1593 @item articulation signs, caused by articulation instructions.
1596 It notably does not work for stems and accidentals (these are caused
1597 by note heads, not by music events) or clefs (these are not caused by
1598 music inputs, but rather by the change of a property value).
1600 There are very few objects which are @emph{directly} connected to
1601 output. A normal note (like @code{c4}) is not directly connected
1605 \tweak #'color #red c4
1609 will not change color. See @ref{Displaying music expressions} for
1613 @node \set vs. \override
1614 @subsection \set vs. \override
1616 We have seen two methods of changing properties: @code{\set} and
1617 @code{\override}. There are actually two different kinds of
1620 Contexts can have properties, which are usually named in
1621 @code{studlyCaps}. They mostly control the translation from
1622 music to notatino, eg. @code{localKeySignature} (for determining
1623 whether to print accidentals), @code{measurePosition} (for
1624 determining when to print a barline). Context properties can
1625 change value over time while interpreting a piece of music;
1626 @code{measurePosition} is an obvious example of
1627 this. Context properties are modified with @code{\set}.
1629 There is a special type of context property: the element
1630 description. These properties are named in @code{StudlyCaps}
1631 (starting with capital letters). They contain the
1632 @q{default settings} for said graphical object as an
1633 association list. See @file{scm/@/define@/-grobs@/.scm}
1634 to see what kind of settings there are. Element descriptions
1635 may be modified with @code{\override}.
1637 @code{\override} is actually a shorthand;
1640 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1644 is more or less equivalent to
1646 @c leave this long line -gp
1648 \set @var{context}.@var{name} #'@var{property} = #(cons (cons '@var{property} @var{value}) <previous value of @var{context})
1651 The value of @code{context} (the alist) is used to initalize
1652 the properties of individual grobs. Grobs also have
1653 properties, named in Scheme style, with
1654 @code{dashed-words}. The values of grob properties change
1655 during the formatting process: formatting basically amounts
1656 to computing properties using callback functions.
1658 @code{fontSize} is a special property: it is equivalent to
1659 entering @code{\override ... #'font-size} for all pertinent
1660 objects. Since this is a common change, the special
1661 property (modified with @code{\set}) was created.
1664 @node Difficult tweaks
1665 @subsection Difficult tweaks
1667 There are a few classes of difficult adjustments.
1673 One type of difficult adjustment is the appearance of spanner objects,
1674 such as slur and tie. Initially, only one of these objects is created,
1675 and they can be adjusted with the normal mechanism. However, in some
1676 cases the spanners cross line breaks. If this happens, these objects
1677 are cloned. A separate object is created for every system that it is
1678 in. These are clones of the original object and inherit all
1679 properties, including @code{\override}s.
1682 In other words, an @code{\override} always affects all pieces of a
1683 broken spanner. To change only one part of a spanner at a line break,
1684 it is necessary to hook into the formatting process. The
1685 @code{after-line-breaking} callback contains the Scheme procedure that
1686 is called after the line breaks have been determined, and layout
1687 objects have been split over different systems.
1689 In the following example, we define a procedure
1690 @code{my-callback}. This procedure
1694 determines if we have been split across line breaks
1696 if yes, retrieves all the split objects
1698 checks if we are the last of the split objects
1700 if yes, it sets @code{extra-offset}.
1703 This procedure is installed into @internalsref{Tie}, so the last part
1704 of the broken tie is translated up.
1706 @lilypond[quote,verbatim,ragged-right]
1707 #(define (my-callback grob)
1709 ; have we been split?
1710 (orig (ly:grob-original grob))
1712 ; if yes, get the split pieces (our siblings)
1713 (siblings (if (ly:grob? orig)
1714 (ly:spanner-broken-into orig) '() )))
1716 (if (and (>= (length siblings) 2)
1717 (eq? (car (last-pair siblings)) grob))
1718 (ly:grob-set-property! grob 'extra-offset '(-2 . 5)))))
1721 \override Tie #'after-line-breaking =
1728 When applying this trick, the new @code{after-line-breaking} callback
1729 should also call the old one @code{after-line-breaking}, if there is
1730 one. For example, if using this with @code{Hairpin},
1731 @code{ly:hairpin::after-line-breaking} should also be called.
1734 @item Some objects cannot be changed with @code{\override} for
1735 technical reasons. Examples of those are @code{NonMusicalPaperColumn}
1736 and @code{PaperColumn}. They can be changed with the
1737 @code{\outputProperty} function, which works similar to @code{\once
1738 \override}, but uses a different syntax,
1742 #"Score.NonMusicalPaperColumn" % Grob name
1743 #'line-break-system-details % Property name
1744 #'((next-padding . 20)) % Value