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 ``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 ``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 ``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
399 If a score ends while an automatic beam has not been ended and is
400 still accepting notes, this last beam will not be typeset at all. The
401 same holds polyphonic voices, entered with @code{<< @dots{} \\ @dots{}
402 >>}. If a polyphonic voice ends while an automatic beam is still
403 accepting notes, it is not typeset.
406 @node Interpretation contexts
407 @section Interpretation contexts
409 This section describes what contexts are, and how to modify them.
412 * Contexts explained::
413 * Creating contexts::
414 * Changing context properties on the fly::
415 * Modifying context plug-ins::
416 * Layout tunings within contexts::
417 * Changing context default settings::
418 * Defining new contexts::
422 @node Contexts explained
423 @subsection Contexts explained
425 When music is printed, a lot of notational elements must be added to the
426 input. For example, compare the input and output of the following example:
428 @lilypond[quote,verbatim,relative=2,fragment]
432 The input is rather sparse, but in the output, bar lines, accidentals,
433 clef, and time signature are added. LilyPond @emph{interprets} the
434 input. During this step, the musical information is inspected in time
435 order, similar to reading a score from left to right. While reading
436 the input, the program remembers where measure boundaries are, and which
437 pitches require explicit accidentals. This information can be presented on
438 several levels. For example, the effect of an accidental is limited
439 to a single staff, while a bar line must be synchronized across the
442 Within LilyPond, these rules and bits of information are grouped in
443 @emph{Contexts}. Some examples of contexts are @context{Voice},
444 @context{Staff}, and @context{Score}. They are hierarchical, for
445 example: a @context{Staff} can contain many @context{Voice}s, and a
446 @context{Score} can contain many @context{Staff} contexts.
449 @image{context-example,5cm,,}
452 Each context has the responsibility for enforcing some notation rules,
453 creating some notation objects and maintaining the associated
454 properties. For example, the @context{Voice} context may introduce an
455 accidental and then the @context{Staff} context maintains the rule to
456 show or suppress the accidental for the remainder of the measure. The
457 synchronization of bar lines is handled at @context{Score} context.
459 However, in some music we may not want the bar lines to be
460 synchronized -- consider a polymetric score in 4/4 and 3/4 time. In
461 such cases, we must modify the default settings of the @context{Score}
462 and @context{Staff} contexts.
464 For very simple scores, contexts are created implicitly, and you need
465 not be aware of them. For larger pieces, such as anything with more
466 than one staff, they must be
467 created explicitly to make sure that you get as many staves as you
468 need, and that they are in the correct order. For typesetting pieces
469 with specialized notation, it can be useful to modify existing or
470 to define new contexts.
473 A complete description of all available contexts is in the program
476 @internalsref{Contexts}.
479 Translation @arrow{} Context.
482 @c [TODO: describe propagation]
485 @node Creating contexts
486 @subsection Creating contexts
488 For scores with only one voice and one staff, contexts are
489 created automatically. For more complex scores, it is necessary to
490 create them by hand. There are three commands that do this.
495 The easiest command is @code{\new}, and it also the quickest to type.
496 It is prepended to a music expression, for example
500 @cindex Context, creating
503 \new @var{type} @var{music expression}
507 where @var{type} is a context name (like @code{Staff} or
508 @code{Voice}). This command creates a new context, and starts
509 interpreting the @var{music expression} with that.
511 A practical application of @code{\new} is a score with many
512 staves. Each part that should be on its own staff, is preceded with
515 @lilypond[quote,verbatim,relative=2,ragged-right,fragment]
522 The @code{\new} command may also give a name to the context,
525 \new @var{type} = @var{id} @var{music}
527 However, this user specified name is only used if there is no other
528 context already earlier with the same name.
534 Like @code{\new}, the @code{\context} command also directs a music
535 expression to a context object, but gives the context an explicit name. The
539 \context @var{type} = @var{id} @var{music}
542 This form will search for an existing context of type @var{type}
543 called @var{id}. If that context does not exist yet, a new
544 context with the specified name is created. This is useful if
545 the context is referred to later on. For example, when
546 setting lyrics the melody is in a named context
549 \context Voice = "@b{tenor}" @var{music}
553 so the texts can be properly aligned to its notes,
556 \new Lyrics \lyricsto "@b{tenor}" @var{lyrics}
561 Another possible use of named contexts is funneling two different
562 music expressions into one context. In the following example,
563 articulations and notes are entered separately,
567 arts = @{ s4-. s4-> @}
570 They are combined by sending both to the same @context{Voice} context,
574 \new Staff \context Voice = "A" \music
575 \context Voice = "A" \arts
578 @lilypond[quote,ragged-right]
582 \new Staff \context Voice = "A" \music
583 \context Voice = "A" \arts
587 With this mechanism, it is possible to define an Urtext (original
588 edition), with the option to put several distinct articulations on the
591 @cindex creating contexts
594 The third command for creating contexts is
596 \context @var{type} @var{music}
601 This is similar to @code{\context} with @code{= @var{id}}, but matches
602 any context of type @var{type}, regardless of its given name.
604 This variant is used with music expressions that can be interpreted at
605 several levels. For example, the @code{\applyOutput} command (see
606 @ref{Running a function on all layout objects}). Without an explicit
607 @code{\context}, it is usually applied to @context{Voice}
610 \applyOutput #'@var{context} #@var{function} % apply to Voice
613 To have it interpreted at the @context{Score} or @context{Staff} level use
617 \context \applyOutput #'Score #@var{function}
618 \context \applyOutput #'Staff #@var{function}
624 @node Changing context properties on the fly
625 @subsection Changing context properties on the fly
629 @cindex changing properties
631 Each context can have different @emph{properties}, variables contained
632 in that context. They can be changed during the interpretation step.
633 This is achieved by inserting the @code{\set} command in the music,
636 \set @var{context}.@var{prop} = #@var{value}
640 @lilypond[quote,verbatim,relative=2,fragment]
642 \set Score.skipBars = ##t
646 This command skips measures that have no notes. The result is that
647 multi-rests are condensed. The value assigned is a Scheme object. In
648 this case, it is @code{#t}, the boolean True value.
650 If the @var{context} argument is left out, then the current bottom-most
651 context (typically @context{ChordNames}, @context{Voice}, or
652 @context{Lyrics}) is used. In this example,
654 @lilypond[quote,verbatim,relative=2,fragment]
656 \set autoBeaming = ##f
661 the @var{context} argument to @code{\set} is left out, so automatic
662 beaming is switched off in the current @internalsref{Voice}. Note that
663 the bottom-most context does not always contain the property that you
664 wish to change -- for example, attempting to set the @code{skipBars}
665 property (of the bottom-most context, in this case @code{Voice}) will
668 @lilypond[quote,verbatim,relative=2,fragment]
674 Contexts are hierarchical, so if a bigger context was specified, for
675 example @context{Staff}, then the change would also apply to all
676 @context{Voice}s in the current stave. The change is applied
677 `on-the-fly', during the music, so that the setting only affects the
678 second group of eighth notes.
682 There is also an @code{\unset} command,
684 \unset @var{context}.@var{prop}
688 which removes the definition of @var{prop}. This command removes
689 the definition only if it is set in @var{context}, so
692 \set Staff.autoBeaming = ##f
696 introduces a property setting at @code{Staff} level. The setting also
697 applies to the current @code{Voice}. However,
700 \unset Voice.autoBeaming
704 does not have any effect. To cancel this setting, the @code{\unset}
705 must be specified on the same level as the original @code{\set}. In
706 other words, undoing the effect of @code{Staff.autoBeaming = ##f}
709 \unset Staff.autoBeaming
712 Like @code{\set}, the @var{context} argument does not have to be
713 specified for a bottom context, so the two statements
716 \set Voice.autoBeaming = ##t
717 \set autoBeaming = ##t
725 Settings that should only apply to a single time-step can be entered
726 with @code{\once}, for example in
728 @lilypond[quote,verbatim,relative=2,fragment]
730 \once \set fontSize = #4.7
735 the property @code{fontSize} is unset automatically after the second
738 A full description of all available context properties is in the
739 program reference, see
741 @internalsref{Tunable context properties}.
744 Translation @arrow{} Tunable context properties.
748 @node Modifying context plug-ins
749 @subsection Modifying context plug-ins
751 Notation contexts (like @code{Score} and @code{Staff}) not only
753 they also contain plug-ins called ``engravers'' that create notation
754 elements. For example, the @code{Voice} context contains a
755 @code{Note_head_engraver} and the @code{Staff} context contains a
756 @code{Key_signature_engraver}.
758 For a full a description of each plug-in, see
760 @internalsref{Engravers}.
763 Program reference @arrow Translation @arrow{} Engravers.
765 Every context described in
767 @internalsref{Contexts}
770 Program reference @arrow Translation @arrow{} Context.
772 lists the engravers used for that context.
775 It can be useful to shuffle around these plug-ins. This is done by
776 starting a new context with @code{\new} or @code{\context}, and
782 \new @var{context} \with @{
795 where the @dots{} should be the name of an engraver. Here is a simple
796 example which removes @code{Time_signature_engraver} and
797 @code{Clef_engraver} from a @code{Staff} context,
799 @lilypond[quote,relative=1,verbatim,fragment]
805 \remove "Time_signature_engraver"
806 \remove "Clef_engraver"
813 In the second staff there are no time signature or clef symbols. This
814 is a rather crude method of making objects disappear since it will affect
815 the entire staff. This method also influences the spacing, which may or
816 may not be desirable. A more
817 sophisticated method of blanking objects is shown in @ref{Common tweaks}.
819 The next example shows a practical application. Bar lines and time
820 signatures are normally synchronized across the score. This is done
821 by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
822 This plug-in keeps an administration of time signature, location
823 within the measure, etc. By moving thes engraver from @code{Score} to
824 @code{Staff} context, we can have a score where each staff has its own
827 @cindex polymetric scores
828 @cindex Time signatures, multiple
830 @lilypond[quote,relative=1,ragged-right,verbatim,fragment]
832 \remove "Timing_translator"
833 \remove "Default_bar_line_engraver"
836 \consists "Timing_translator"
837 \consists "Default_bar_line_engraver"
843 \consists "Timing_translator"
844 \consists "Default_bar_line_engraver"
853 @node Layout tunings within contexts
854 @subsection Layout tunings within contexts
856 Each context is responsible for creating certain types of graphical
857 objects. The settings used for printing these objects are also stored by
858 context. By changing these settings, the appearance of objects can be
861 The syntax for this is
864 \override @var{context}.@var{name} #'@var{property} = #@var{value}
867 Here @var{name} is the name of a graphical object, like @code{Stem} or
868 @code{NoteHead}, and @var{property} is an internal variable of the
869 formatting system (`grob property' or `layout property'). The latter is a
870 symbol, so it must be quoted. The subsection @ref{Constructing a
871 tweak} explains what to fill in for @var{name}, @var{property}, and
872 @var{value}. Here we only discuss the functionality of this command.
877 \override Staff.Stem #'thickness = #4.0
881 makes stems thicker (the default is 1.3, with staff line thickness as a
882 unit). Since the command specifies @context{Staff} as context, it only
883 applies to the current staff. Other staves will keep their normal
884 appearance. Here we see the command in action:
886 @lilypond[quote,verbatim,relative=2,fragment]
888 \override Staff.Stem #'thickness = #4.0
894 The @code{\override} command changes the definition of the @code{Stem}
895 within the current @context{Staff}. After the command is interpreted
896 all stems are thickened.
898 Analogous to @code{\set}, the @var{context} argument may be left out,
899 causing it to default to @context{Voice}, and adding @code{\once} applies
900 the change during one timestep only
902 @lilypond[quote,fragment,verbatim,relative=2]
904 \once \override Stem #'thickness = #4.0
909 The @code{\override} must be done before the object is
910 started. Therefore, when altering @emph{Spanner} objects such as slurs
911 or beams, the @code{\override} command must be executed at the moment
912 when the object is created. In this example,
914 @lilypond[quote,fragment,verbatim,relative=2]
915 \override Slur #'thickness = #3.0
917 \override Beam #'thickness = #0.6
922 the slur is fatter but the beam is not. This is because the command for
923 @code{Beam} comes after the Beam is started, so it has no effect.
925 Analogous to @code{\unset}, the @code{\revert} command for a context
926 undoes an @code{\override} command; like with @code{\unset}, it only
927 affects settings that were made in the same context. In other words, the
928 @code{\revert} in the next example does not do anything.
931 \override Voice.Stem #'thickness = #4.0
932 \revert Staff.Stem #'thickness
935 Some tweakable options are called ``subproperties'' and reside inside
936 properties. To tweak those, use commands of the form
938 @c leave this as a long long
940 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
947 \override Stem #'details #'beamed-lengths = #'(4 4 3)
953 Internals: @internalsref{OverrideProperty}, @internalsref{RevertProperty},
954 @internalsref{PropertySet}, @internalsref{Backend}, and
955 @internalsref{All layout objects}.
960 The back-end is not very strict in type-checking object properties.
961 Cyclic references in Scheme values for properties can cause hangs
965 @node Changing context default settings
966 @subsection Changing context default settings
968 The adjustments of the previous subsections (@ref{Changing context
969 properties on the fly}, @ref{Modifying context plug-ins}, and
970 @ref{Layout tunings within contexts}) can also be entered separately
971 from the music in the @code{\layout} block,
980 \override Stem #'thickness = #4.0
981 \remove "Time_signature_engraver"
986 Here @code{\Staff} takes the existing definition for context @context{Staff} from the
987 identifier @code{\Staff}.
992 \override Stem #'thickness = #4.0
993 \remove "Time_signature_engraver"
997 affect all staves in the score. Other contexts can be modified
1000 The @code{\set} keyword is optional within the @code{\layout} block, so
1016 It is not possible to collect context changes in a variable and apply
1017 them to a @code{\context} definition by referring to that variable.
1019 The @code{\RemoveEmptyStaffContext} will overwrite your current
1020 @code{\Staff} settings. If you wish to change the defaults for a
1021 staff which uses @code{\RemoveEmptyStaffContext}, you must do so
1022 after calling @code{\RemoveemptyStaffContext}, ie
1027 \RemoveEmptyStaffContext
1029 \override Stem #'thickness = #4.0
1035 @node Defining new contexts
1036 @subsection Defining new contexts
1038 Specific contexts, like @context{Staff} and @code{Voice}, are made of
1039 simple building blocks. It is possible to create new types of
1040 contexts with different combinations of engraver plug-ins.
1042 The next example shows how to build a different type of
1043 @context{Voice} context from scratch. It will be similar to
1044 @code{Voice}, but only prints centered slash noteheads. It can be used
1045 to indicate improvisation in jazz pieces,
1047 @lilypond[quote,ragged-right]
1048 \layout { \context {
1050 \type "Engraver_group"
1051 \consists "Note_heads_engraver"
1052 \consists "Text_engraver"
1053 \consists Pitch_squash_engraver
1054 squashedPosition = #0
1055 \override NoteHead #'style = #'slash
1056 \override Stem #'transparent = ##t
1060 \accepts "ImproVoice"
1064 a4 d8 bes8 \new ImproVoice { c4^"ad lib" c
1065 c4 c^"undress" c_"while playing :)" c }
1071 These settings are defined within a @code{\context} block inside a
1072 @code{\layout} block,
1082 In the following discussion, the example input shown should go on the
1083 @dots{} in the previous fragment.
1085 First the context's name is defined. Instead of @context{Voice} it
1086 will be called @context{ImproVoice},
1092 Since it is similar to the @context{Voice}, we want commands that work
1093 on (existing) @context{Voice}s to remain working. This is achieved by
1094 giving the new context an alias @context{Voice},
1100 The context will print notes, and instructive texts
1103 \consists Note_heads_engraver
1104 \consists Text_engraver
1107 but only on the center line,
1110 \consists Pitch_squash_engraver
1111 squashedPosition = #0
1114 The @internalsref{Pitch_squash_engraver} modifies note heads (created
1115 by @internalsref{Note_heads_engraver}) and sets their vertical
1116 position to the value of @code{squashedPosition}, in this case@tie{}@code{0},
1119 The notes look like a slash, and have no stem,
1122 \override NoteHead #'style = #'slash
1123 \override Stem #'transparent = ##t
1126 All these plug-ins have to cooperate, and this is achieved with a
1127 special plug-in, which must be marked with the keyword @code{\type}.
1128 This should always be @internalsref{Engraver_group},
1131 \type "Engraver_group"
1134 Put together, we get
1139 \type "Engraver_group"
1140 \consists "Note_heads_engraver"
1141 \consists "Text_engraver"
1142 \consists Pitch_squash_engraver
1143 squashedPosition = #0
1144 \override NoteHead #'style = #'slash
1145 \override Stem #'transparent = ##t
1151 Contexts form hierarchies. We want to hang the @context{ImproVoice}
1152 under @context{Staff}, just like normal @code{Voice}s. Therefore, we
1153 modify the @code{Staff} definition with the @code{\accepts}
1164 The opposite of @code{\accepts} is @code{\denies},
1165 which is sometimes needed when reusing existing context definitions.
1167 Putting both into a @code{\layout} block, like
1177 \accepts "ImproVoice"
1182 Then the output at the start of this subsection can be entered as
1190 c c_"while playing :)"
1199 @node The \override command
1200 @section The \override command
1202 In the previous section, we have already touched on a command that
1203 changes layout details: the @code{\override} command. In this section,
1204 we will look in more detail at how to use the command in practice.
1208 * Constructing a tweak::
1209 * Navigating the program reference::
1210 * Layout interfaces::
1211 * Determining the grob property::
1212 * Objects connected to the input::
1213 * \set vs. \override::
1214 * Difficult tweaks::
1219 @node Constructing a tweak
1220 @subsection Constructing a tweak
1222 Commands which change output generally look like
1225 \override Voice.Stem #'thickness = #3.0
1229 This means that we must determine these bits of information:
1232 @item the context: here @context{Voice}.
1233 @item the layout object: here @code{Stem}.
1234 @item the layout property: here @code{thickness}.
1235 @item a sensible value: here @code{3.0}.
1238 Some tweakable options are called ``subproperties'' and reside inside
1239 properties. To tweak those, use commands in the form
1242 \override Stem #'details #'beamed-lengths = #'(4 4 3)
1245 @cindex internal documentation
1246 @cindex finding graphical objects
1247 @cindex graphical object descriptions
1250 @cindex internal documentation
1252 We demonstrate how to glean this information from the notation manual
1253 and the program reference.
1256 @node Navigating the program reference
1257 @subsection Navigating the program reference
1259 Suppose we want to move the fingering indication in the fragment
1262 @lilypond[quote,fragment,relative=2,verbatim]
1268 If you visit the documentation on fingering instructions (in
1269 @ref{Fingering instructions}), you will notice:
1274 Program reference: @internalsref{Fingering}.
1279 @c outdated info; probably will delete.
1281 This fragment points to two parts of the program reference: a page
1282 on @code{FingerEvent} and one on @code{Fingering}.
1284 The page on @code{FingerEvent} describes the properties of the music
1285 expression for the input @code{-2}. The page contains many links
1286 forward. For example, it says
1289 Accepted by: @internalsref{Fingering_engraver},
1293 That link brings us to the documentation for the Engraver, the
1297 This engraver creates the following layout objects: @internalsref{Fingering}.
1300 In other words, once the @code{FingerEvent}s are interpreted, the
1301 @code{Fingering_engraver} plug-in will process them.
1305 @c I can't figure out what this is supposed to mean. -gp
1307 The @code{Fingering_engraver} is also listed to create
1308 @internalsref{Fingering} objects,
1310 @c old info? it doesn't make any sense to me with our current docs.
1312 second bit of information listed under @b{See also} in the Notation
1316 Follow the link to @internalsref{Fingering}. At the top of the
1320 Fingering objects are created by: @internalsref{Fingering_engraver} and
1321 @internalsref{New_fingering_engraver}.
1324 By clicking around in the program reference, we can follow the
1325 flow of information within the program, following links like this:
1329 @item @internalsref{Fingering}:
1330 @internalsref{Fingering} objects are created by:
1331 @internalsref{Fingering_engraver}
1333 @item @internalsref{Fingering_engraver}:
1334 Music types accepted: @internalsref{fingering-event}
1336 @item @internalsref{fingering-event}:
1337 Music event type @code{fingering-event} is in Music expressions named
1338 @internalsref{FingerEvent}
1341 This path goes against the flow of information in the program: it
1342 starts from the output, and ends at the input event. You could
1343 also start at an input event, and read with the flow of
1344 information, eventually ending up at the output object(s).
1346 The program reference can also be browsed like a normal document. It
1347 contains chapters on
1349 @internalsref{Music definitions},
1352 @code{Music definitions}
1354 on @internalsref{Translation}, and the @internalsref{Backend}. Every
1355 chapter lists all the definitions used and all properties that may be
1359 @node Layout interfaces
1360 @subsection Layout interfaces
1362 @cindex interface, layout
1363 @cindex layout interface
1366 The HTML page that we found in the previous section describes the
1367 layout object called @internalsref{Fingering}. Such an object is a
1368 symbol within the score. It has properties that store numbers (like
1369 thicknesses and directions), but also pointers to related objects. A
1370 layout object is also called a @emph{Grob}, which is short for Graphical
1371 Object. For more details about Grobs, see @internalsref{grob-interface}.
1373 The page for @code{Fingering} lists the definitions for the
1374 @code{Fingering} object. For example, the page says
1377 @code{padding} (dimension, in staff space):
1383 which means that the number will be kept at a distance of at least 0.6
1387 Each layout object may have several functions as a notational or
1388 typographical element. For example, the Fingering object
1389 has the following aspects
1393 Its size is independent of the horizontal spacing, unlike slurs or beams.
1396 It is a piece of text. Granted, it is usually a very short text.
1399 That piece of text is typeset with a font, unlike slurs or beams.
1402 Horizontally, the center of the symbol should be aligned to the
1403 center of the notehead.
1406 Vertically, the symbol is placed next to the note and the staff.
1409 The vertical position is also coordinated with other superscript
1410 and subscript symbols.
1413 Each of these aspects is captured in so-called @emph{interface}s,
1414 which are listed on the @internalsref{Fingering} page at the bottom
1417 This object supports the following interfaces:
1418 @internalsref{item-interface},
1419 @internalsref{self-alignment-interface},
1420 @internalsref{side-position-interface}, @internalsref{text-interface},
1421 @internalsref{text-script-interface}, @internalsref{font-interface},
1422 @internalsref{finger-interface}, and @internalsref{grob-interface}.
1425 Clicking any of the links will take you to the page of the respective
1426 object interface. Each interface has a number of properties. Some of
1427 them are not user-serviceable (``Internal properties''), but others
1430 We have been talking of @emph{the} @code{Fingering} object, but actually it
1431 does not amount to much. The initialization file (see
1432 @ref{Default files})
1433 @file{scm/@/define@/-grobs@/.scm} shows the soul of the `object',
1438 (avoid-slur . around)
1439 (slur-padding . 0.2)
1440 (staff-padding . 0.5)
1441 (self-alignment-X . 0)
1442 (self-alignment-Y . 0)
1443 (script-priority . 100)
1444 (stencil . ,ly:text-interface::print)
1445 (direction . ,ly:script-interface::calc-direction)
1446 (font-encoding . fetaNumber)
1447 (font-size . -5) ; don't overlap when next to heads.
1448 (meta . ((class . Item)
1449 (interfaces . (finger-interface
1451 text-script-interface
1453 side-position-interface
1454 self-alignment-interface
1455 item-interface))))))
1459 As you can see, the @code{Fingering} object is nothing more than a
1460 bunch of variable settings, and the webpage in the Program Reference
1461 is directly generated from this definition.
1464 @node Determining the grob property
1465 @subsection Determining the grob property
1467 Recall that we wanted to change the position of the @b{2} in
1469 @lilypond[quote,fragment,relative=2,verbatim]
1475 Since the @b{2} is vertically positioned next to its note, we have to
1476 meddle with the interface associated with this positioning. This is
1477 done using @code{side-position-interface}. The page for this interface
1481 @code{side-position-interface}
1483 Position a victim object (this one) next to other objects (the
1484 support). The property @code{direction} signifies where to put the
1485 victim object relative to the support (left or right, up or down?)
1490 Below this description, the variable @code{padding} is described as
1495 (dimension, in staff space)
1497 Add this much extra space between objects that are next to each other.
1501 By increasing the value of @code{padding}, we can move the
1502 fingering away from the notehead. The following command inserts
1503 3 staff spaces of white
1504 between the note and the fingering:
1506 \once \override Voice.Fingering #'padding = #3
1509 Inserting this command before the Fingering object is created,
1510 i.e., before @code{c2}, yields the following result:
1512 @lilypond[quote,relative=2,fragment,verbatim]
1513 \once \override Voice.Fingering #'padding = #3
1520 In this case, the context for this tweak is @context{Voice}. This
1521 fact can also be deduced from the program reference, for the page for
1522 the @internalsref{Fingering_engraver} plug-in says
1525 Fingering_engraver is part of contexts: @dots{} @internalsref{Voice}
1529 @node Objects connected to the input
1530 @subsection Objects connected to the input
1534 In some cases, it is possible to take a short-cut for tuning graphical
1535 objects. For objects that result directly from a piece of the input,
1536 you can use the @code{\tweak} function, for example
1538 @lilypond[relative=2,fragment,verbatim,ragged-right]
1541 \tweak #'color #red d
1543 \tweak #'duration-log #1 a
1544 >4-\tweak #'padding #10 -.
1547 As you can see, properties are set directly in the objects directly,
1548 without mentioning the grob name or context where this should be
1551 This technique only works for objects that are directly connected to
1552 an @internalsref{event} from the input, for example
1555 @item note heads, caused by chord-pitch (i.e., notes inside a chord).
1556 @item articulation signs, caused by articulation instructions.
1559 It notably does not work for stems and accidentals (these are caused
1560 by note heads, not by music events) or clefs (these are not caused by
1561 music inputs, but rather by the change of a property value).
1563 There are very few objects which are @emph{directly} connected to
1564 output. A normal note (like @code{c4}) is not directly connected
1568 \tweak #'color #red c4
1572 will not change color. See @ref{Displaying music expressions} for
1576 @node \set vs. \override
1577 @subsection \set vs. \override
1579 We have seen two methods of changing properties: @code{\set} and
1580 @code{\override}. There are actually two different kinds of
1583 Contexts can have properties, which are usually named in
1584 @code{studlyCaps}. They mostly control the translation from
1585 music to notatino, eg. @code{localKeySignature} (for determining
1586 whether to print accidentals), @code{measurePosition} (for
1587 determining when to print a barline). Context properties can
1588 change value over time while interpreting a piece of music;
1589 @code{measurePosition} is an obvious example of
1590 this. Context properties are modified with @code{\set}.
1592 There is a special type of context property: the element
1593 description. These properties are named in @code{StudlyCaps}
1594 (starting with capital letters). They contain the
1595 ``default settings'' for said graphical object as an
1596 association list. See @file{scm/@/define@/-grobs@/.scm}
1597 to see what kind of settings there are. Element descriptions
1598 may be modified with @code{\override}.
1600 @code{\override} is actually a shorthand;
1603 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1607 is more or less equivalent to
1609 @c leave this long line -gp
1611 \set @var{context}.@var{name} #'@var{property} = #(cons (cons '@var{property} @var{value}) <previous value of @var{context})
1614 The value of @code{context} (the alist) is used to initalize
1615 the properties of individual grobs. Grobs also have
1616 properties, named in Scheme style, with
1617 @code{dashed-words}. The values of grob properties change
1618 during the formatting process: formatting basically amounts
1619 to computing properties using callback functions.
1621 @code{fontSize} is a special property: it is equivalent to
1622 entering @code{\override ... #'font-size} for all pertinent
1623 objects. Since this is a common change, the special
1624 property (modified with @code{\set}) was created.
1627 @node Difficult tweaks
1628 @subsection Difficult tweaks
1630 There are a few classes of difficult adjustments.
1636 One type of difficult adjustment is the appearance of spanner objects,
1637 such as slur and tie. Initially, only one of these objects is created,
1638 and they can be adjusted with the normal mechanism. However, in some
1639 cases the spanners cross line breaks. If this happens, these objects
1640 are cloned. A separate object is created for every system that it is
1641 in. These are clones of the original object and inherit all
1642 properties, including @code{\override}s.
1645 In other words, an @code{\override} always affects all pieces of a
1646 broken spanner. To change only one part of a spanner at a line break,
1647 it is necessary to hook into the formatting process. The
1648 @code{after-line-breaking} callback contains the Scheme procedure that
1649 is called after the line breaks have been determined, and layout
1650 objects have been split over different systems.
1652 In the following example, we define a procedure
1653 @code{my-callback}. This procedure
1657 determines if we have been split across line breaks
1659 if yes, retrieves all the split objects
1661 checks if we are the last of the split objects
1663 if yes, it sets @code{extra-offset}.
1666 This procedure is installed into @internalsref{Tie}, so the last part
1667 of the broken tie is translated up.
1669 @lilypond[quote,verbatim,ragged-right]
1670 #(define (my-callback grob)
1672 ; have we been split?
1673 (orig (ly:grob-original grob))
1675 ; if yes, get the split pieces (our siblings)
1676 (siblings (if (ly:grob? orig)
1677 (ly:spanner-broken-into orig) '() )))
1679 (if (and (>= (length siblings) 2)
1680 (eq? (car (last-pair siblings)) grob))
1681 (ly:grob-set-property! grob 'extra-offset '(-2 . 5)))))
1684 \override Tie #'after-line-breaking =
1691 When applying this trick, the new @code{after-line-breaking} callback
1692 should also call the old one @code{after-line-breaking}, if there is
1693 one. For example, if using this with @code{Hairpin},
1694 @code{ly:hairpin::after-line-breaking} should also be called.
1697 @item Some objects cannot be changed with @code{\override} for
1698 technical reasons. Examples of those are @code{NonMusicalPaperColumn}
1699 and @code{PaperColumn}. They can be changed with the
1700 @code{\outputProperty} function, which works similar to @code{\once
1701 \override}, but uses a different syntax,
1705 #"Score.NonMusicalPaperColumn" % Grob name
1706 #'line-break-system-details % Property name
1707 #'((next-padding . 20)) % Value