Everyone's heard of I Am T-Pain, Pandora, and Turntable.fm but app developers on the next bleeding edge are pushing the envelope with features from the stunningly practical to the wildly "out-there" that many within the industry may not have heard of before. Within these entertaining apps lies advanced technology with practical applications across the board. Let's take a tour of the most advanced, wackiest music apps that exist -- or are on their way to existing.