Re: "unroll code"

[Andrew Bernard]

Well, despite that I think this is an absolutely terrible hack, exporting to 
midi and importing it back produces more or less what you want, with a lot of 
editing. Works on 2.19.41 on openSUSE Leap 42.1 linux.

Still interested to know why you want to do this.

Andrew

== snip

Using your input:

\version "2.14.0"

\layout {
  \context {
    \Voice
    \remove "Note_heads_engraver"
    \consists "Completion_heads_engraver"
    \remove "Rest_engraver"
    \consists "Completion_rest_engraver"
  }
}

trackAchannelA = {

  % [TEXT_EVENT] creator:

  % [TEXT_EVENT] GNU LilyPond 2.19.41

  \time 4/4

  \tempo 4 = 60

}

trackA = <<
  \context Voice = voiceA \trackAchannelA
>>


trackBchannelA = {

  \set Staff.instrumentName = "\new:"

}

trackBchannelB = \relative c {
  a'4 b c, d
  | % 2
  a' b c, d
  | % 3
  a' b c, d
  | % 4
  a' b c, d
  | % 5
  e f g a
  | % 6
  a b c, d
  | % 7
  e f g a
  | % 8

}

trackB = <<

  \clef bass

  \context Voice = voiceA \trackBchannelA
  \context Voice = voiceB \trackBchannelB
>>


\score {
  <<
    \context Staff=trackB \trackA
    \context Staff=trackB \trackB
  >>
  \layout {}
  \midi {}
}