Instant Jam uses the music in your own music library, matching it to note charts for "the world's most popular songs." It supports the keyboard or USB guitar controllers, and allows in-game music purchases through Amazon or iTunes -- its version of DLC, which also happens to enhance your regular music library.
A beta is currently available through Facebook. Versions playable through the website and embeddable elsewhere will be rolled out soon, and the team promises additional features regularly.
