Once you cough up the dough, you'll get to read a little essay about how the song "connects spatial relationships in nature and music, and uses them to represent emotional states," and then you'll get to play a nifty little game where you fly through a series of tunnels picking up crystals off the wall. And then, I don't know... I guess that's it, and you can go back to playing Angry Birds until the next song/app is released?
(If this matters at all, the song itself is really great, built on an arhythmic, high-pitched tapping sound and a stop-start beat that gets progressively crazier as the end nears. The vocals are as powerful and dynamic as we've come to expect, refreshingly unaffected and direct, though points are deducted for the line "I'm blinded by the light," which, come on. Listen here if you can't be bothered with the app stuff, although, jeez, just give it a shot.)