The Multichord musical instrument is an acoustic stringed instrument with a single string, constructed from wood, a hard drive, 20-lb monofilament, and assorted electronic components. It was the culmination of a project to build an acoustic instrument capable of playing multiple notes without fretting or manual, time-consuming retuning. The Multichord achieves this by attaching a hard drive read/write head assembly between the resonant string and a tensioning spring to adjust the tension of the instrument’s string. Careful adjustment was made to the tension of both the string and the spring with the hard drive head in a neutral, unpowered position to ensure a bipolar application of voltage within the safety ratings of the hard drive’s coil could cause the string to cover a full musical octave. In the end, the Multichord was tuned to a C-major scale (no flats or sharps) running from A at 220Hz through (but not including) A at 440Hz.

[via Hack a Day]