Actually getting the beats out of the Arduino required the addition of a R2R DAC circuit and a TDA2822 amplifier. In the video after the break, you can hear the results for yourself. [joekutz] is ...

The project features a brilliant idea for input: He uses a 1/8″ TRS connector (mini-jack) whose tip is the input to the DAC of the Arduino. There are conductive pads in the shape of a keyboard ...