Strange MIDI output bug

[Mark Cookson]

I've just installed Lilypond 2.4.2 (running on
Mandrake Linux 9.2) and have started entering some of
the Mozart Clarinet Concerto for the mutopia project.

I'm having some trouble getting the midi output to
come out with the correct transpositions. I've
condensed the problem into the file at the bottom of
this email.

As written, the midi transpositions come out fairly
surprising (try it and see!)
Oddly though, if I comment out all of the lines:
R2.*8
then the transposition works fine, although Lilypond
then prints a warning:

warning: FIXME: key change merge 
(I'm not sure if this means that you're already aware
of the problem?)

I can also fix the midi output by altering the \score
block to use four separate staves rather than using
\partcombine.

Thanks in advance for any light you can shed on the
problem.

Mark Cookson
PS Now that I've had some time to get my head around
the workings of Lilypond, is there anything a fairly
non-technical user like me can do to help on the
documentation side of things? 



***************

\include "english.ly"
\version "2.4.2"

     global = {
        \time 3/4
        
     }
fluteOne = \relative c''' {
  \set Staff.midiInstrument = "flute"
  
  \key d \major
  \clef treble

  R2.*8

  a2.\f  ~
  a2.
  a4.( d8 fs, a)
  a8( g) fs4 r4
  e2 ( fs4)
  e4( a8) cs( b a')
  a,2 \appoggiatura cs16 b8.( a16)
  a4 r4 r4
}
fluteTwo = \relative c'' {
  \set Staff.midiInstrument = "flute"
  
  \key d \major
  \clef treble

  R2.*8

  a4\f( d4. fs8)
  fs8( e) d4 r4
  fs2( d8 fs)
  e4( d4) r4
  cs2( d4)
  cs4.( e8 fs d)
  cs2 \appoggiatura e16 d8.( cs16)
  cs4 r4 r4
}


hornOne = \relative c'' {
  \set Staff.midiInstrument = "french horn"
  \transposition d
  \key c \major
  \clef treble

  R2.*8

  g4\f( c4. e8)
  e8( d) c4 r4
  g4.( c8 e g)
  g8( f) e4 r4

  d2( e4)
  d2( e4)
  d2. ~
  d4 r4 r4

}

hornTwo = \relative c' {
  \set Staff.midiInstrument = "french horn"
  \transposition d
  \key c \major
  \clef treble

  R2.*8

  e4\f e4.( g8)
  g4( e4) r4
  e4.( g8 c e)
  d4( c4) r4
  g2( c4)
  g2( c4)
  d2.(
  g,4) r4 r4

}


     \score {
        \new StaffGroup <<
          \new Staff << \set Staff.instrument =
"Flutes" \global \partcombine  \fluteOne  \fluteTwo >>
          \new Staff << \set Staff.instrument = "Horns in D"
\global \partcombine \hornOne \hornTwo >>

        >>
        \layout { }
        \midi { \tempo 4=100}
     }

***************


                
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