Minor update to Gregorian section of NR (issue 109230044 by address@hidden)

[PhilEHolmes]

Reviewers: ,

Message:
Please review

Description:
Some minor changes to the "Transcribing Gregorian chant" section of the
NR: this positions the comment about stems more closely to the example
it refers to, and rationalises some removes and hides.

Please review this at https://codereview.appspot.com/109230044/

Affected files (+14, -11 lines):
  M Documentation/notation/ancient.itely


Index: Documentation/notation/ancient.itely
diff --git a/Documentation/notation/ancient.itely  
b/Documentation/notation/ancient.itely
index  
67aefbd86d0fbb92a38dec37565962d91c9f8029..e4ded2fa4f88b7a93582d05e085085e49e6b43d0  
100644
--- a/Documentation/notation/ancient.itely
+++ b/Documentation/notation/ancient.itely
@@ -2699,13 +2699,6 @@ the @code{Stem_engraver} from the Voice context:
 @}
 @end example

-However, in some transcription styles, stems are used
-occasionally, for example to indicate the transition from a
-single-tone recitative to a fixed melodic gesture.  In these cases,
-one can use either @code{\hide Stem} or
address@hidden Stem.length = #0} instead, and restore the stem
-when needed with the corresponding @code{\once \override Stem.transparent  
= ##f} (see example below).
-
 @b{Timing.} For unmetered chant, there are several alternatives.

 The Time_signature_engraver can be removed from the Staff context
@@ -2751,7 +2744,10 @@ verba = \lyricmode {
       \Staff
       \remove "Time_signature_engraver"
       \remove "Bar_engraver"
-      \hide Stem
+    }
+    \context {
+      \Voice
+      \remove "Stem_engraver"
     }
   }
 }
@@ -2759,17 +2755,25 @@ verba = \lyricmode {

 This works fine, as long as the text doesn't span a line break.  If
 that is the case, an alternative is to add hidden notes to the
-score, here in combination with changing stem visibility:
+score, as below.

+In some transcription styles, stems are used
+occasionally, for example to indicate the transition from a
+single-tone recitative to a fixed melodic gesture.  In these cases,
+one can use either @code{\hide Stem} or
address@hidden Stem.length = #0} instead of @code{\remove}-ing
+the @code{Stem_engraver} and restore the stem
+when needed with the corresponding @code{\undo \hide Stem}.

 @lilypond[verbatim,ragged-right]
 \include "gregorian.ly"
 chant = \relative c' {
   \clef "G_8"
   \set Score.timing = ##f
+  \hide Stem
   c\breve \hide NoteHead  c c c c c
   \undo \hide NoteHead
-  \override Stem.transparent = ##f \stemUp c4 b4 a
+  \undo \hide Stem \stemUp c4 b4 a
   \hide Stem c2 c4  \divisioMaior
   c\breve \hide NoteHead c c c c c c c
   \undo \hide NoteHead c4 c f, f \finalis
@@ -2790,7 +2794,6 @@ verba = \lyricmode {
       \Staff
       \remove "Time_signature_engraver"
       \hide BarLine
-      \hide Stem
     }
   }
 }