"Currently your Arduino can only beep like a microwave oven. Mozzi brings your Arduino to life by allowing it to produce much more complex and interesting growls, sweeps and chorusing atmospherics. These sounds can be quickly and easily constructed from familiar synthesis units like oscillators, delays, filters and envelopes.
You can use Mozzi to generate algorithmic music for an installation or performance, or make interactive sonifications of sensors, on a small, modular and super cheap Arduino, without the need for additional shields, message passing or external synths." Ooooooh