The idea: You can collect music you can play. To collect music you can play, you have to find compositions, which are basically just recipes but for playing instruments.To play you have to have the right instrument used specific to the music. But to unlock songs to be played, you have to complete a mini game. The mini game is just like Guitar Hero where you anticipate notes and hit them at the right time.
Also there will be a free style mode where your action bar keys become notes that you can play in what ever order you want. You can also compose/record your free style and be able to play it like the other music you collected.
Playing music would give a variety of buffs to other players depending on the music being played.