Um, it turns your iPhone into a trombone. That's all ye know and all ye need to know. You blow into the microphone at the bottom of the phone to produce a note, and move the slider on the on-screen leaf (a bit like a party blower) to change the pitch.
It gets better. The community is working to create more music for your leaf trombone; it's similar to Guitar Hero in that little leaves stream into view telling you where to position the slider and when to blow, though it can be hard to see. The result is, well, dependent on the skill of the player…
The best bit is you can perform on a world stage; other users can log on, listen to you, and rate your performance.
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