i don't know if this would be better under tech or even math... for an end of the year calc project, me and some friends are trying to get a stephen hawking-sounding voice to rap a little about calculus. so far we got the voice part outputted to an mp3. it doesn't quite sound like him a la mc hawking, but it's close enough. here's where we're having trouble: we're trying to get some background music in, like beats and such. is there a way to filter voices out of pre-existing music, so we can just swap voices? i found some software to create the actual music tracks, but that seems too hard. also, is there a way to merge two or more tracks (like one voice track and a music track) so the play at the same time? any outstanding software you'd recommend for this?