Past 6 (or 7) Makes it basically, (well) useless. I upgraded the music a bunch of times, and now I want to go back. Add new sounds or just make some kind of playlist that let's you choose any track you'd like to listen to. Max level (10) is just a plain joke. I warn you. (seriously!) You'll be sorry if you do so!!!
 "Coffee Clicker"){kind=icon}