syntax questions (polyphony: staff changes & al.)

[Vaclav Smilauer]

Several questions and one suggestion. Thanks for comments.

1) Can I set various (named) voice properties from a different voice 
(like stem direction)? Say I have a 3-voice piece in a piano staff; the 
middle voice switches staves often (manually), so I define someting like 
staffUp = { \change Staff = up \voiceTwo } and similarly also staffDown. 
However, at the moment of \staffUp, I would like to make the upper voice 
\voiceOne and the lower one \oneVoice (and vice versa, \oneVoice and 
\voiceFour). Can I do that somehow without touching the other two voices 
directly, from the middle one?

2) With staff autochanging, can I define some sort of callback 
functions, called when the autochanged voice goes up or down (think of 
stem direction in this very voice and also (sub 1) for the other 
voices)? As is, the staff autochanging (for middle voice, 3 voices 
total) is for me virtually useless for it will not change stem direction 
so there are always stem collisions (either in the lower or the upper 
staff).

3) if I use { ... \\ ... \\ ...} in several voices simlutaneously, it 
does not work correctly. I assume this has to do with automatic voice 
creation and some internal overlaps. Any fix for this (besides \new 
Voice...)?

4) Somewhat related, what is the most simple way to define a \function 
that can take fixed number of arguments? Do I need scheme for this?

5) I propose an intuitive syntax idiom for \noBeam: c[], marking the c 
standalone, without beam. Currently, this makes lilypond warn about beam 
having less than 2 stems, eventually discarding the beam.

Vaclav S.