Next time you're stumped what to do with an old hard drive take a look below at what Shantea has done. It's not only environmentally friendly, but is also super cool in that he's used the hard disk spinning function to create a turntable MIDI controller, called Ceylon.
As Hackaday tell us, 'The faster you spin it, the higher the amplitude and frequency. These signals are far too weak to be sampled directly by a microcontroller, and for digital control '" as in, MIDI '" you don't need to read the analog signals anyway. These signals were turned digital with the help of an LM339 quad comparator.'
This MIDI controller uses the OpenDeck Platform that allows anyone to create their own MIDI controllers and devices.
Full info, including how it was built: https://shanteacontrols.wordpress.com/2015/02/24/building-ceylon/