Several people have pointed out the omission of this classic app. I've now spent quite a lot of time with it and have given it merely an Awesome! rating. I know this is not going to be a popular opinion, but that's the beauty of the guide. You can go leave your thoughts now, or simply insist that I'm out of my fucking mind for not making it Essential.

In my defense I'd like to point out that the focus of the guide is on iPad apps and iPad usage; as I state in the review:

On iPhones this is practically an Essential app, you really can jam with just your thumbs, but on larger iPad screens the experience is a little awkward to play.

It's still amazing for all that it can do, don't shoot!

iPad Music App Buyer’s Guide Rating: Awesome!

Recommendation: For playing sampled instruments, or with Virtual MIDI, there is a lot to like here.