"Filtering" expressions?

[Alexander Deubelbeiss]

Hi there,

is there a way to remove certain types of events
from an existing music expression? To be specific,
I want to strip vocal-specific things (mostly breath
marks) from the voices in a 4-part a cappella piece
and condense (partcombine) everything into a piano
grand staff for the rehearsal pianist.

My low-tech way to handle these cases has been to
copy-and-paste the voices' finished variable
definitions into new names, remove the piano-irrelevant
material and then \partcombine the modified copies.
This is obviously a little awkward in cases where you
suddenly find out that the voices weren't actually
quite finished, because any further corrections have
to be made in two places to keep the two copies in
sync.

But applying a systematic search-and-replace to a
copy of some data sounds like just the sort of job
that I should be leaving to a computer. Does Lilypond
provide something of that nature, or should I start
learning scheme?

(Another option I'm aware of is to add rather than 
subtract -- i.e. to have the common material in one 
definition and the once-only stuff in another which
is then added as "simultaneous music" where it
belongs in the layout. I've tried that, but found it
counterintuitive to both write and read, and no gain
over the modified-copy approach in terms of the 
"examine output, correct silly mistakes in the input"
feedback cycle.)

-- 
GMX DSL-Flatrate 1 Jahr kostenlos* + WLAN-Router ab 0,- Euro*
Bis 31.12.2005 einsteigen! Infos unter: http://www.gmx.net/de/go/dsl