How does the Infinite Jukebox get its track IDs?

So, seven months later, I'm at the point where I can open up a page's source and see how it gets its information. (in Python, no less)

http://hasteb.in/nucefeyegi.py

Turns out there's a json api that gets called with all the information in it (example: http://static.echonest.com/infinite_jukebox_data/TRYDDPR1401CA91AAF.json )

Sorry for not replying sooner, and sorry for the necro, and sorry for the slightly-off-topic post.