Issue 3905: Doc: Clarify grace note sync workaround

As pointed out in the thread
http://lists.gnu.org/archive/html/lilypond-user/2014-04/msg00540.html
it is necessary to use \grace for the old grace note sync issue.
This commit makes that explicit in the known issues section in the NR

diff --git a/Documentation/notation/rhythms.itely b/Documentation/notation/rhythms.itely
index 9ca613ed753d4e025dac2bbfdcd9d3a4fb3ce5b1..72c963cdb7d84b3e3c2baea0968984a27ce2cbbf 100644 (file)
--- a/Documentation/notation/rhythms.itely
+++ b/Documentation/notation/rhythms.itely
@@ -3511,6 +3511,12 @@ durations in the other staves.  For the above example
 >>
 @end lilypond
 
+Please make sure that you use the @code{\grace} command for the
+spacer part, even if the visual part uses @code{\acciaccatura} or
+@code{\appoggiatura} because otherwise an ugly slur fragment will
+be printed, connecting the invisible grace note with the following
+note.
+
 The use of grace notes within voice contexts confuses the way the voice
 is typeset. This can be overcome by inserting a rest or note between the
 voice command and the grace note.