There is a program called "Jamstix" and I have hoped it might someday solve this problem. I've been updating since it first appeared but have yet to really understand or master it. It has many drum samples which are probably useable and I also use it driving a Roland TD-20 head via MIDI. My trouble is time and I have spent precious little of it trying to learn how it works (hoping to eventually but you know how that goes). Anyway, it does seem like a cool approach.