Smule has quickly become my favorite iPhone app developer.
It's not that their apps have been particularly useful, but they're the ones I get the most excited about. From Sonic Lighter to Sonic Boom and Sonic Vox, these guys are IMO currently the masters of fun, cool, quirky iPhone apps.
Now they're going completely bohemian with their latest release, Ocarina. According to Smule, this is the first true musical instrument for the iPhone with no precompiled riffs.
By simply blowing into your iPhone's mic you'll create sound, and by holding the "holes" on the screen you'll be able to create music. After some practice, that is.
You have the option of choosing between modes including Dorian, Lydian, or my personal favorite--Zeldarian. With Zeldarian, you'll be able to play the Zelda theme from The Legend of Zelda: Ocarina of Time.
Smule's site teaches the basics, from how to hold your new instrument to how to lightly blow. It even has an online score generator that lets you translate music into Smule's Ocarina language by telling you the proper fingering to create the song you want.
By far my favorite feature, though, is the ability to listen to other people playing all over the world in real time. There's just something really cool about being able to hear a guy in Japan play Mozart from a world away.
Ocarina is available from the App Store for 99 cents.