MAKE subscriber Jeff made this really sweet laser synth-guitar that he calls The Prism.

The Prism is a laser guitar, with four laser beams acting as “strings” that can be held to produce a tone. A Sharp IR range finder detects the musician’s hand on the fretboard to change the pitch. You can select sine, tri or square waveform outputs, and introduce classic synthesizer effects like sync, skew and LFO.

Full instructions (it’s quite a complex project) are up on Instructables.