To make a simple MIDI controller, you need knowledge of ... circuit board that serves to break out the connections on an Arduino nano to a dozen arcade push buttons, four slide pots, two rotary ...

This means that using this firmware, music software such as Max, Ableton, Reaktor etc can read and write MIDI directly to/from the Arduino. Currently the project is for direct USB-MIDI ...

Apart from understanding the Arduino's code ... and can also be powered via USB and the VIN pin. The price difference between the two boards is minimal too, with the Nano available at $24.90 ...