Re: Issue 1620 in lilypond: Midi overflow with instrument changes

[lilypond]

Comment #1 on issue 1620 by jan.nieuwenhuizen: Midi overflow with  
instrument changes
http://code.google.com/p/lilypond/issues/detail?id=1620

@PhilEHolmes says: the current versions of LP add extra tracks, which  
2.13.50 (which I've used for comparison) didn't

Just to be perfectly clear about this: 2.13.50 (up till 52 I think) used to  
merge
voices into one track and channel, making any multi-voice MIDI output  
unusable
for postprocessing.

Also, the MIDI code has had comments and remarks for over 10 years that  
suggest
that voices should be mapped to channels (to be able to do sensible post  
processing
etc), which my first MIDI patch finally did.

The regression as shown here is open for discussion, as far as I'm  
concerned.
LilyPond by default now supports having more than 16 staves, as long as the
number of instruments keeps below 15 (+ percussion).  Also, all voices are
preserved.

If this new feature is something that we want to keep, it looks like we
need to keep several different MIDI output modes.  I don't see how we
can support this new > 16 staves feature when midiInstruments are being
changed several times per staff.

When changing instruments, it is quite clear that this can only work
in midiChannelMapping = #'staff mode (at least not in the default
#'instrument mode).

Attached is a patch that may fix this regression, as long as
midiChannelMapping = #'staff is used.

However, this example is still very complicated and it's unclear
to me if this patch solves this problem.



Attachments:
        0001-MIDI-in-midiChannelMapping-staff-mode-keep-to-one-ch.patch  835 
bytes