I'll be honest -- since the first Ocarina app came out, I've become a fan of Smule, the company behind it. Its mix of creative energy and technical know-how is a great match for Apple and a good example of software made well. But I have never really been a fan of Ocarina the app, just because I think blowing into your iPhone is kind of silly.
Ocarina 2 doesn't dissuade that notion. It's about the same app as the first one, though Smule has wisely applied all of its knowledge from the intervening years, including a sort of Magic Piano-style play mode, as well as the freemium "get some tunes free, pay for more" model from Smule's past few games. There is still a freestyle mode to play with, as well as a world mode that lets you hear what other users are playing from around the rest of the globe.
Ocarina 2 is a smooth, well-packaged app, and if you loved the first version, you'll enjoy this update. The freemium features might turn some people off, but in general, Ocarina 2 is a good time for players of all ages. I just wish it wasn't quite so, you know, silly.