This one's a bit complicated. It's a single string slide guitar constructed from parts of an old CD player. The mechanism that would normally move the laser backwards and forwards across the CD is mounted above the string, and in place of the laser there is a metal slide.

On the left of the picture is a motor with a plastic cable-tie 'plectrum' attached which plucks the string as it rotates, powered by the USB cable. The motor which controls the laser sled position is attached to the same motor in a separate, fully-functioning CD player (not in the picture).

This separate CD player is set to 'random play' and plays a scratched CD of hawaiian music samples. As the laser skips and jumps on the CD, the slide moves in the same way on the guitar, changing the pitch of the note played when the motor plucks the string.

Sled Guitar mp3 clip