acid music studio is a loop based program, having never used garage band, it sounds like its based on the same principle. Acid MS is not intended as a multitrack recorder, but is nice as a mixing platform for a novice/hobbyist. I love acid because it is extremely easy to use "out of the box".
If you want to record your own music, you may want to look into a multi-track recorder program...i can't suggest any that I've used, I record using a digital multitracker (mr8)then I mix in Acid. On this BBS alot of folks rave about a program called N-track. I've never tried it, but I believe the latest version is like $70 (24bit/96kbs), but there is a version for like 40bucks that doesn't support 24/96...
For 15-20 bucks, the acid is a steal! enjoy