This instructable shows you how to build a light controlled sound generator. Here i've built an unstable feedback sculpture with the sound generator and a candle. The speaker makes the candle flicker and the light from the candle modulates the signal headed for the speaker. Air turbulence makes the relation between the speaker and the candle unsteady, so it bounces between different semi-stable modes.
The circuit to create and amplify the sound isn't trivial, but it's made of simple building blocks. I'll show you how to build a light sensor with a CdS photoresistor, a simple op-amp preamp, an oscillator with the classic LM555, and a 5 watt power amplifier with the LM1875.
You can do it if you follow the instructions, I'll try to explain the details.