http://www.youtube.com/watch?v=xzoJBfUODbA#t=22​

Although it sounds like a pipe organ in a cathedral, the sound producing mechanisms are very different. Instead of pipes and a wind chest, it uses electromagnets and steel tines to produce 20 chromatic notes, starting at middle C, with full polyphony.
Each tine is coupled with an electromagnet that outputs PWM at its fundamental pitch. The pull and release of the tine by the magnet causes a sustaining effect.
The soundboard under the bridge is mahogany and the body is made of bubinga. Inside it houses a small Arduino micro-controller that accepts MIDI input that controls 20 polyphonic software oscillators (like 20 function generators). These are stepped up to 30 volt pulses via 3 ULN 2803 Darlington drivers to the magnets.

via

Code:

http://www.synthtopia.com/content/2014/11/18/the-tine-organ/#more-59890