Hi Bebu, after getting the violin, every time you enter a room there will be some waves of enemies trying to destroy the violin. You can't kill them if you're holding the violin so you'll have to place the violin on a shrine while you kill them until the wave ends. Shrines are the little black platforms that appear in the center of each room (like the one from which you get the violin). I'm planning to make this more evident on a future update, thanks for your comment and for trying out my game :)