While scanning a copy of Nuts & Volts, I happened on an ad by Ramsey Electronics. This ad featured several electronics kits, one of which was the Laser Lght Show, # LLS1.  I ordered a kit and assembled the thing in about 6 hours. 

Basically, an optical path is set up wherein a laser beam reflects off of two variable speed motors with mirrors and a speaker with a mirror to provide a sound modulated Lissajous pattern. Lissajous (Wikipedia) patterns are an exercise in signal mixing.  Off-axis sinusoidal waves can be mixed electronically (see link) or optically as with this kit.  The kit has a jack to feed audio to the speaker. I have not had a chance to feed in audio just yet- need to open up a cheapo radio and do some minor surgery.

It is satisfying to build things now and then. This activity stems from to my basic belief that one can never know too much about electronics. And, it’s fun.