I'm looking for great iPad apps for creating beats, backing tracks, or remixing songs. Not in that lame (but genius) I Am T-Pain kinda way, but in the way of something like Sony Acid Pro or Pro Tools but touch friendly. Anyone have pros/cons for me on some great apps? Would also need loops and instrument tracks. MIDI and full drum kit would be a plus, as would the ability to song sample from the library on the device. Thx in advance.