X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=Documentation%2Fuser%2Fchanging-defaults.itely;h=b63980e924431bc738d5dba35a20ff9a648fa636;hb=1423508c355989fa26a8cfe5985b0d6e1ab0a538;hp=9962c220d07507995ebf9eda8f04adadbdfca5b4;hpb=5c9c9c0ae6cd4bed8f7a2c62b2c014f3659a188a;p=lilypond.git

diff --git a/Documentation/user/changing-defaults.itely b/Documentation/user/changing-defaults.itely
index 9962c220d0..b63980e924 100644
--- a/Documentation/user/changing-defaults.itely
+++ b/Documentation/user/changing-defaults.itely
@@ -7,7 +7,7 @@
     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
@@ -57,6 +57,7 @@ This section describes what contexts are, and how to modify them.
 @menu
 * Contexts explained::
 * Creating contexts::
+* Keeping contexts alive::
 * Modifying context plug-ins::
 * Changing context default settings::
 * Defining new contexts::
@@ -402,6 +403,156 @@ these forms
 
 @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
@@ -602,6 +753,7 @@ to indicate improvisation in jazz pieces,
   \name ImproVoice
   \type "Engraver_group"
   \consists "Note_heads_engraver"
+  \consists "Rhythmic_column_engraver"
   \consists "Text_engraver"
   \consists Pitch_squash_engraver
   squashedPosition = #0
@@ -1480,7 +1632,7 @@ command to remain immediately adjacent to the object to which it is
 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
@@ -1521,12 +1673,12 @@ and @code{\tweak} may be used to modify any single occurrence of
 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
@@ -1799,6 +1951,15 @@ indicator is @strong{always} required before
 @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
@@ -1836,6 +1997,17 @@ TrillPitchAccidental - not tried
 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
@@ -3109,6 +3281,11 @@ Notation Reference:
 @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
@@ -3157,13 +3334,16 @@ scaling can be achieved by applying the same transformation to the
 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  }
 >>