The absolute cheapest way to record music. Without counting in the computer and you're using a $82 soundblaster from sim lim square is.
1. buy the magazine computer music. There's always a cd on it that has a free multitrack app, a sampler, a synth and free samples. $19.95 at certain shops.
2. get the small lavalier mics for MD players. Surprisingly they're quite good, though they emphasize more within the vocal range. Don't know how much the bog standard ones retail for, but the newer sony's are 80-120.
If you need to record bass, you can plug it into the mic in of the soundcard. Just remember not to let the recording levels clip, and that the recording is dry. So you'll need a reverb plugins to make it sound nice. Try the kjaerhus plugs. Free plugins for everything. Next you might want to check out the guys from smart electronix. They have more radical sound mangling plugs. For sweetening up try the elogoxa exciter.