So I do some electronic music on the side and I noticed that PSP, DS, GP2x, etc have lots of little synth, sampler, drum machine programs ported to/developed for them. Any chance something like that happened for xbox and I just happened to miss it?

Well, I'll take your silence as a no then. Anybody interested in porting some open-source music software to xbox? I would, but I don't have the skills.