Ocarina, the second iPhone application from Silicon Valley based Smule, has surged to the top spot on the iPhone App store just a little over a week after launching (you can download it here for $.99).

Why? Just like Smule’s first application, a social virtual lighter (yeah, I know), People are fascinated by interacting with others. With the lighter it was competing geographically for the brightest light. With Ocarina, it’s listening to the music of others.

Ocarina, named after an ancient flute-like wind instrument, lets people play haunting, flute-like songs by blowing into the iPhone microphone and hitting the virtual buttons.

Yay. But the cool thing is you can hit a button and listen to what other Ocarina users are playing around the world. It’s social music, and strangely compelling. The company says Oscarina users have have listened to more than three million melodies. You can listen to some of them here.