version that you are working on. See TRANSLATION for details.
@end ignore
-@c \version "2.11.65"
+@c \version "2.12.0"
@node Changing defaults
@chapter Changing defaults
@menu
* Contexts explained::
* Creating contexts::
+* Keeping contexts alive::
* Modifying context plug-ins::
* Changing context default settings::
* Defining new contexts::
@end itemize
+@node Keeping contexts alive
+@subsection Keeping contexts alive
+
+@cindex contexts, keeping alive
+@cindex contexts, lifetime
+
+Contexts are usually terminated at the first musical moment in
+which they have nothing to do. So @code{Voice} contexts die as
+soon as they contain no events; @code{Staff} contexts die as soon
+as all the @code{Voice} contexts within them contain no events; etc.
+This can cause difficulties if earlier contexts which have died
+have to be referenced, for example, when changing staves with
+@code{\change} commands, associating lyrics with a voice with
+@code{\lyricsto} commands, or when adding further musical events to
+an earlier context.
+
+There is an exception to this general rule: just one of the
+@code{Voice} contexts in a @code{Staff} context or in a
+@code{<<...>>} construct will always persist to the end of the
+enclosing @code{Staff} context or @code{<<...>>} construct, even
+though there may be periods when it has nothing to do. The context
+to persist in this way will be the first one encountered in the
+first enclosed @code{@{...@}} construct, ignoring any in enclosed
+@code{<<...>>} constructs.
+
+Any context can be kept alive by ensuring it has something to do at
+every musical moment. @code{Staff} contexts are kept alive by
+ensuring one of their voices is kept alive. One way of doing this
+is to add spacer rests to a voice in parallel with the real music.
+These need to be added to every @code{Voice} context which needs to
+be kept alive. If several voices are to be used sporadically it is
+safest to keep them all alive rather than attempting to rely on the
+exceptions mentioned above.
+
+In the following example, both voice A and voice B are kept alive
+in this way for the duration of the piece:
+
+@lilypond[quote,verbatim]
+musicA = \relative c'' { d4 d d d }
+musicB = \relative c'' { g4 g g g }
+keepVoicesAlive = {
+ <<
+ \new Voice = "A" { s1*5 } % Keep Voice "A" alive for 5 bars
+ \new Voice = "B" { s1*5 } % Keep Voice "B" alive for 5 bars
+ >>
+}
+
+music = {
+ \context Voice = "A" {
+ \voiceOneStyle
+ \musicA
+ }
+ \context Voice = "B" {
+ \voiceTwoStyle
+ \musicB
+ }
+ \context Voice = "A" { \musicA }
+ \context Voice = "B" { \musicB }
+ \context Voice = "A" { \musicA }
+}
+
+\score {
+ \new Staff <<
+ \keepVoicesAlive
+ \music
+ >>
+}
+@end lilypond
+
+@cindex lyrics, aligning with sporadic melody
+
+The following example shows how a sporadic melody line with lyrics
+might be written using this approach. In a real situation the
+melody and accompaniment would consist of several different
+sections, of course.
+
+@lilypond[quote,verbatim]
+melody = \relative c'' { a4 a a a }
+accompaniment = \relative c' { d4 d d d }
+words = \lyricmode { These words fol -- low the mel -- o -- dy }
+\score {
+ <<
+ \new Staff = "music" {
+ <<
+ \new Voice = "melody" {
+ \voiceOne
+ s1*4 % Keep Voice "melody" alive for 4 bars
+ }
+ {
+ \new Voice = "accompaniment" {
+ \voiceTwo
+ \accompaniment
+ }
+ <<
+ \context Voice = "melody" { \melody }
+ \context Voice = "accompaniment" { \accompaniment }
+ >>
+ \context Voice = "accompaniment" { \accompaniment }
+ <<
+ \context Voice = "melody" { \melody }
+ \context Voice = "accompaniment" { \accompaniment }
+ >>
+ }
+ >>
+ }
+ \new Lyrics \with { alignAboveContext = #"music" }
+ \lyricsto "melody" { \words }
+ >>
+}
+@end lilypond
+
+An alternative way, which may be better in many circumstances, is
+to keep the melody line alive by simply including spacer notes to
+line it up correctly with the accompaniment:
+
+@lilypond[quote,verbatim]
+melody = \relative c'' {
+ s1 % skip a bar
+ a4 a a a
+ s1 % skip a bar
+ a4 a a a
+}
+accompaniment = \relative c' {
+ d4 d d d
+ d4 d d d
+ d4 d d d
+ d4 d d d
+}
+words = \lyricmode { These words fol -- low the mel -- o -- dy }
+
+\score {
+ <<
+ \new Staff = "music" {
+ <<
+ \new Voice = "melody" {
+ \voiceOne
+ \melody
+ }
+ \new Voice = "accompaniment" {
+ \voiceTwo
+ \accompaniment
+ }
+ >>
+ }
+ \new Lyrics \with { alignAboveContext = #"music" }
+ \lyricsto "melody" { \words }
+ >>
+}
+@end lilypond
+
@node Modifying context plug-ins
@subsection Modifying context plug-ins
\name ImproVoice
\type "Engraver_group"
\consists "Note_heads_engraver"
+ \consists "Rhythmic_column_engraver"
\consists "Text_engraver"
\consists Pitch_squash_engraver
squashedPosition = #0
to apply after the input file has been converted to a music stream.
This is often not the case, as many additional elements are inserted
into the music stream implicitly. For example, when a note which is
-not part of a chord is processed, Lilypond implicitly inserts a
+not part of a chord is processed, LilyPond implicitly inserts a
@code{ChordEvent} event before the note, so separating the tweak
from the note. However, if chord symbols are placed round the
tweak and the note, the @code{\tweak} command comes after the
these items.
Notably the @code{\tweak} command cannot be used to modify stems,
-beams or accidentals, since these are generated later by note heads,
-rather than by music elements in the input stream. Nor can a
-@code{\tweak} command be used to modify clefs or time signatures,
-since these become separated from any preceding @code{\tweak}
-command in the input stream by the automatic insertion of extra
-elements required to specify the context.
+beams or accidentals directly, since these are generated later by
+note heads, rather than by music elements in the input stream.
+Nor can a @code{\tweak} command be used to modify clefs or time
+signatures, since these become separated from any preceding
+@code{\tweak} command in the input stream by the automatic
+insertion of extra elements required to specify the context.
But the @code{\tweak} command can be used as an alternative to
the @code{\override} command to modify those notational elements
@item articulation shortcuts, e.g. @code{-.}, @code{->}, @code{--}
@end itemize
+These indications affect only the next note.
+
+@lilypond[verbatim,quote,relative=2]
+c2( c)
+c2_( c)
+c2( c)
+c2^( c)
+@end lilypond
+
@strong{The direction property}
The position or direction of many layout objects is controlled
TrillPitchGroup - not tried
@end ignore
+These indications affect all notes until they are cancelled.
+
+@lilypond[verbatim,quote,relative=2]
+c2( c)
+\slurDown
+c2( c)
+c2( c)
+\slurNeutral
+c2( c)
+@end lilypond
+
@node Distances and measurements
@node Modifying ties and slurs
@unnumberedsubsubsec Modifying ties and slurs
+@cindex slurs, modifying
+@cindex ties, modifying
+@cindex Bézier curves
+@cindex Bézier control points
+
Ties, slurs and phrasing slurs are drawn as third-order Bézier
curves. If the shape of the tie or slur which is calculated
automatically is not optimum, the shape may be modified manually by
curve's control points.
For the example above the following override gives a satisfactory
-tie:
+tie. Note the placement -- it has to be immediately before the note
+to which the start of the tie (or slur) is attached.
@lilypond[verbatim,quote,relative=1]
<<
- \once \override Tie
- #'control-points = #'((1 . -1) (3 . 0.6) (12.5 . 0.6) (14.5 . -1))
- { e1 ~ e1 }
+ {
+ \once \override Tie
+ #'control-points = #'((1 . -1) (3 . 0.6) (12.5 . 0.6) (14.5 . -1))
+ e1 ~ e1
+ }
\\
{ r4 <g c,> <g c,> <g c,>4 }
>>
projects / lilypond.git / blobdiff