The many instruments are played identically -- by tapping on the screen in response to audio and visual cues. Said visual cues include the Butt-Biting Bug flying towards groups of stars; when he contacts a star, the player is to tap the screen. Successful taps increase a meter, which, when full, triggers a butt-biting vignette. The lessons unlock special games like the voice-training lesson, in which players actually sing into the mic.
We're still a bit flabbergasted that the weird song about biting butts became popular enough to support a game, which is now a real thing that someone bought.
Hey kids, Namco Bandai's 
