I've been privileged enough to have the time to try learn a few musical instruments, but never got any good at them. But there's another way to play music, by writing programs, that is like my day job? I've just started looking into this so I'm sure I've missed quite a bit. I recommend the interactive manual to start:
This was prompted by some music I like which was apparently written in csound. Then I realised this csound was also part of the OLPC.
It also had a red-headed stepchild in MPEG-4 Structured Audio, but this seems to be a dead end. Time is better spent learning csound.
... and why maybe not to use it
Interesting, considering I favour non-Von Neumann paradigms for general-purpose programming, csound is like the audio equivalent of Fortran.