After seeing from gnat that there are over 500 (!) proposals in for presentations this year, I'm not particularly optimisitc about a music one getting in. Web services, p2p, etc. should probably be ahead of me in the queue; there ain't any venture capital in ambient music.
I'm going ahead on it anyway, simply because the music software available for Linux simultaneously is unbelievably brilliant and sucks really hard at the same time.
All of the packages mentioned above are the musical equivalent of assembly language or barely above. csound thinks of everything as a scalar. You can create pseudo-arrays with "generator" functions, but these have to be referred to by number, as do files (no, not filehandles, numbers, just like in Fortran). cmix does a little better, with a c-like language called Minc (Minc is not C); cmusic uses full C syntax, but requires the edit/compile/run/swear/repeat cycle. And there's no gloabl way to talk about a musical phrase or manipulate it in the program - everything's:
"Here's a note on this instrument, starting at this time, and going this long. Now here's another one. And another. And another. Now let's write a loop which generates something else, one note at a time."
I feel like one of those guys in the mall, spending his days painting people's names on a grain of rice.
Cmix has a perl interface, but it's an old-style "build a Perl that contains these new functions" interface, not a modern one (and it doesn't quite work, either).
Complaints aside, it's really wonderful to hear the incredible noises that any of these programs can make. cmix has a new real-time version which actually works pretty well; I'm probably going to use it as my sound-production backend.