Szymon Kaliski has put together a Raspberry Pi, some buttons and potentiometers and a lot of circuitry to build a four-track audio looper. You can record four eight-second loops and then adjust their playback with the buttons and potentiometers to achieve the sound you want. It’s all highly technical, but he’s written up what he can and placed it and the code onto Github. See it in action below:

LoopPI from Szymon Kaliski on Vimeo.