Issue 2022 in lilypond: MIDI percussion lost in implicit voices

[lilypond]

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

New issue 2022 by address@hidden: MIDI percussion lost in implicit  
voices
http://code.google.com/p/lilypond/issues/detail?id=2022

Reported by Raphael Frey:
Hey there!

There are at least three ways to enter polyphonic percussion music (see  
examples below). However the first (easiest) approach does not produce any  
Midi output in polyphonic parts.

% first example - no midi output starting from bar 2
\version "2.14.2"
\score {
  \new DrumStaff <<
    \drummode {
      bd4 sn4 bd4 sn4
      << {
        \repeat unfold 16 hh16
      } \\ {
        bd4 sn4 bd4 sn4
      } >>
    }
  >>
  \midi { }
  \layout { }
}


% second example - no problem here

\version "2.14.2"
\score {
  \new DrumStaff
    \new DrumVoice {
      \drummode {
        bd4 sn4 bd4 sn4
        <<
          {
            \voiceOne
            \repeat unfold 16 hh16
          }
          \new DrumVoice {
            \voiceTwo
            bd4 sn4 bd4 sn4
          }
        >>
      }
    }
  \midi { }
  \layout { }
}


% third example - no problem here
\version "2.14.2"
\score {
  \new DrumStaff <<
    \new DrumVoice {
      \drummode {
        \oneVoice
        bd4 sn4 bd4 sn4
        \voiceOne
        \repeat unfold 16 hh16
      }
    }
    \new DrumVoice {
      \drummode {
        \voiceTwo
        s1 bd4 sn4 bd4 sn4
      }
    }
  >>
  \midi { }
  \layout { }
}

%%%%%%%%%%%%%%%%%%%

This may relate to issues 1647 and 1648, as Raphael's workaround is to  
declare the DrumVoices explicitly.