How to manually set MIDI channel # for a staff?

[Jason Yip]

Hi,

Does anyone know how to manually set the midi channel # for a staff to 
something other than the default of channel 0/1? Without having to 
create dummy staffs with just `s256` as the voice content preceding the 
desired staff? The staff in question usually only has one voice, so I 
modified the midi context as shown below simply made a bunch of dummy 
voices with only `s256` as the content so that they don't at least 
affect the graphical output:

```
     \midi {
      \context {
        \Staff
        \remove "Staff_performer"
      }
      \context {
        \Voice
        \consists "Staff_performer"
      }
    }
```

It's definitely a hacky solution, especially given that my program that 
automatically generates lilypond code has to output `\new Voice { s256 
}\n` n - 1 times before the actual content then wrap the voices with << 
>>. If this is the only way to do it, is there some sort of way to 
substitute `s256` with something else that doesn't occupy length but at 
least lets the performer still assign a channel to the dummy staff/voices?

Thanks!