FourTrack

$9.99 (iTunes link)

FourTrack is a deceptively simple-looking multitrack recorder and mixing console. If you're a songwriter looking for a way to sketch multi-instrumental song ideas on the go, FourTrack acts as a fully baked portable recording studio.

Pros: Familiar interface for anyone who's worked with recording gear, real-time volume metering, track bouncing for limitless layering, and support for dock-connecting stereo microphones.

Cons: The app is relatively expensive, iPod Touch users will need to purchase a mic or headset, and recordings only transfer over Wi-Fi with no option to e-mail or upload to a Web host.