Issue 1677 in lilypond: Partcombine misses notes

[lilypond]

Status: Accepted
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 1677 by address@hidden: Partcombine misses notes
http://code.google.com/p/lilypond/issues/detail?id=1677

Reported by Nels Daily and analysed by Reinhold:

A short analysis of the bug:

The disappearing notes start after a multi-measure rest, which did start
earlier than a multi-measure rest in the first voice. The part-combiner  
walks through the score as following:
1) In the first measure, only mI is playing, so it starts a solo (mII has a  
multi-measure rest) and uses only the music events from mI
2) In the second measure both voices have a multi-measure rest, the solo of  
mI has ended. As mII has a multi-measure rest already going on, the  
part-combiner needs to take the multi-measure rest from mI (the  
part-combiner is not able to split up a multi-measure rest!)
3) In the third measure, mII has a rest, so the first quarter is still  
detected as unisilence (thus the rest from mI is still used). Now, as there  
is already a whole measure rest going on, lilypond ignores the following  
notes.


Note that there are some other bugs in the part-combiner that can be seen  
with this example:

-) If one replaces the r4 with a b4 in measure 3, then the notes are  
displayed (marked as "Solo II", but the whole-measure rest from mI is  
displayed, too.
-) If one adds a measure "c1" to both voices, the "r4" in mI is wrongly
printed as a full-measure rest (rests in unisilence are taken from the  
second voice, unless voice one had a solo ending before the rest, like in  
the original example)
-) If one adds any note after the "R1*2" in mI, then the notes are  
correctly printed.

As Xavier already mentioned, there is a workaround to force the  
partcombiner to use a particular combining strategy. (Also note that the  
first quarter eight rest in the third measure of your original example is  
printed as if there were two voices present... Also in this case you need  
to tell the part-combiner that the rest should be a solo, too. Don't worry,  
the "Solo" text will still be printed on the first note, not on the rest).

\version "2.15.0"

mI = \relative c' {
  r4 e e e |
  R1*2
}

mII = \relative c' {
  R1*2
%% These notes don't appear!!! %%
  r4 b b b
}

\score{ <<
  \partcombine \mI \mII

}


Attachments:
        pc.png  2.1 KB