Oh sorry, I didn't mean all-in-one as in it can do everything, just that it can handle synthesis and composition. I guess "batteries included" might be a better term, what I really meant was something that needs no external sources for either sound or sequencing, you can make a track from start to end without needing to use something else.

Of course, supercollider does indeed fit this role, but as I've said I do have problems with it. Currently I'm looking at using a generic language, with some synthesis and composition modules. Suprisingly, game frameworks (e.g. Love2D) are looking promising for this, so that could be good, if a little bit overkill.