To date, sonification apps are rare. Music apps on the other hand are widely used. Smartphone users like to play with music. In this manuscript, we present Mixing Levels, a spirit level sonification based on music mixing. Tilting the smartphone adjusts the volumes of 5 musical instruments in a rock music loop. Only when perfectly leveled, all instruments in the mix are well-audible. The app is supposed to be useful and fun. Since the app appears like a music mixing console, people have fun to interact with Mixing Levels, so that learning the sonification is a playful experience.