Music hacks are my favourite hacks of all, and this one had me bounding around the office with the video below playing on my laptop so I could share it with people yesterday. Meet Quaver, the multiplayer piano. With a Raspberry Pi, some magnetic pickups, and the open-source Sooper Looper (which I am downloading as soon as I have finished writing this post), Mike and Sean from MajorMega  hacked an old upright piano into an instrument that can loop up to four separate tracks, and then upload your results to the internet to be listened to when you get home

Go here to see the original:
Quaver, the analogue looping piano