The Solar Powered Theremin
James Watt has created a Solar powered theremin that you can make at home with just basic soldering skills. For true Do-It-Yourself authenticity, the whole instrument is housed in an ALTOIDS mint tin.
“The device functions best on bright sunny cloudless days. By simply flipping open the lid and letting the light hit the solar panel the theremin will generate a high musical note. In order to play a tune you can either cast a shadow over the panel with your hand (this allows you to play with an action very similar to the original theremin) or you can tilt and angle the theremin in relation to the sun to vary the note. With practice you can pick out notes very precisely and in optimal weather the device will generate tones over several octaves so it is possible to play real music on the thing unlike some low cost conventional theremin kits which can generate little more than squeaks and squawks.”
More information on the Solar Powered Theremin.