Seline HD: Hot damn. I played with Seline HD, a gorgeous, futuristic music making app, for about half an hour and I still don't know what I'm doing (I skipped the help documentation), but I can already tell that this, moreso than 90% of the other music apps I've used, sees the potential for the iPad as a music making device. Very interesting UI and a huge variety of options, including an ergonomic, split playing surface, a selection of 20 odd instruments and several drone sounds, and the ability to overdub recordings on top of yourself—it's pricey, but as one of the most ambitious apps I've seen on the iPad, period, it's allowed to be. $9