Disclaimer: I'm german. English is not my foreign language. Forgive me all the faults. Now we have the awesome ABC music system, that allows us to play , replay musicnotes and tracks ingame. Besides from giving the game a interaction method between players, the music system could influence some of the monster behaviour. 1)If you play an instrument it could change some friendly monsters to into "hostile status". When you stop to play, the monsters will change ther status back to friendly. 2) Some Monsters may like a specific instrument and will get friendly as long as you play the instrument. There are endless posibilities, but i think these are the easiest to implement in the game. These characteristics don't need to be on every Mobtype, but could be a way to defeat Boss Monsters.