Re: Doc: Issue 4059: Document MIDI mapping and MIDI effects (issue 249980043 by address@hidden)

[Keith OHara]

On Mon, 06 Jul 2015 15:19:20 -0700, <address@hidden> wrote:

> > Setting
> > midiChannelMapping to 'voice often prevents the context properties
> > from having effect."
>
> Doesn't the paragraph under 'voice above explain explicitly what
> happens?  That seems better than the rather vague "often prevents the
> context properties ...".  There already is a reference back to that
> explanation.

I didn't think the paragraph under 'voice sufficiently discouraged its use.  It 
describes a first-approximation of the behavior, but the description isn't 
complete, and the behavior isn't transparent:
\score{
  \new Staff <<
    \new Voice = "violin" {
      c'4
      % set the voice below to flute
      \set Staff.midiInstrument = "flute"
      r g' r }
    \new Voice = "flute" {
      % set the voice above to violin
      \set Staff.midiInstrument = "violin"
      r4 c' r g' } >>
  \layout{}
  \midi{\context {\Score midiChannelMapping=#'voice }}

I don't think midiChannelMapping='voice has any use.  Somebody added the code 
under sponsorship from Fruity Loops Sequencer, so if it has any use it is in 
conjunction with that software, so let the sponsor document it there.

That programmer who added the code didn't know about Lilypond's 
engraver/performer method of routing events and property-changes to output, and 
didn't know much about midi, so the data flow doesn't make much sense in the 
context of Lilypond and MIDI.