@MeechMunchie, 1 week later - As a kid I was given an ancient (Windows 95) version of a midi sequencer called Cakewalk which was a simple and powerful tool back in the day which did what you described. The company still do business and their new software is apparently still good.
Take a look. You may have to dig a bit to find what you're looking for. Doesn't seem cheap, though.
EDIT: Their Music Creator 6 is currently £10 on steam for the next 29 hours (11:03am GMT) and may do what you want. I'll PM you about it.
On topic: Here, some crap.
Hmm, this sounds like a terrible idea! Glad it never caught on! :P
Redneck TV: