it's been years since i've used or even seen it, but i remember sony acid as being an interesting application. and i know it's come along way since spending time with it.

as i recall, it's primarily a loop based workstation and you can purchase different license-free libraries and build your own music from there. ok, so actually, it's not really license-free since you're essentially paying for the right to use the library for your own ends.

anyway, it now looks like a full blown DAW with audio and midi capabilities, which it was not a few years ago.

i'm not sure if that's what you mean by software to help compose.

reason might be another way to go.

all the best.
keith