Audacity is a good audio editing program & is free. But it doesn't sound like that's what you're looking for.
If you need a music recording program, I know a few good apps you could use, but neither of them are free. There's GarageBand(also on Macs, but simpler as the app) for the iPad, where you can easily record music, but it's also really good. Also, there's Xewton Music Studio for all Apple portable devices, which doesn't sound as realistic as GB, but is still good. Either way, both are pretty expensive, but are both worth it(I have both).
Hope this helped.
---Bill