When you launch Ocarina.app, you are presented with four buttons that control the pitch. You make sounds with the Ocarina by blowing into the microphone on the iPhone. You control the pitch of the sound by pressing one, two, or all of the four blue buttons. The more air you blow through the mic, the louder the sound gets. You can also tilt your iPhone up/down to change the vibrato depth, and left/right to change the vibrato rate.
All of this is cool, but the real magic happens when you tap the green button just above the home button. A small menu appears, and allows you to tap on a globe. In the world view, you can hear other Ocarina players around the world as they toot along to jingles and their favorite songs. You can even rate the player's performance by tapping the little heart next to their name. If music isn't the player's forte, then press the fast forward button to skip them.
I've used the application over the weekend, and have really liked it so far. I would like to see a favorites list added. It would be nice to mark certain players as favorites and be able to instantly start listening to them again. You can purchase Ocarina from the iTunes App Store for $.99 (US). Note that you must have an iPhone to use this application (no iPod touch).