The Thingamagoops are really just simple, analog type synthesizers that you control in a different way.

The Thingamagoops have oscillators just like any synth. On analog synths the oscillator that creates the actual tone you hear is called a VCO or voltage controlled oscillator. The Bleeps work a little differently so we'll just call it the main oscillator. Instead of using a keyboard, the main oscillator in the Thingamas is controlled by a photocell. Here's what the waveform from the main oscillator looks like.

When there is a lot of light hitting it, the resistance across the photocell goes up and the oscillator yields a higher pitch. Less light lowers the resistance and pitch. When the switch on the right is up, the oscillator is in a high range and when it's down it's in a lower range.
One neat thing about the photocell is that it reacts to different kinds of light. Florescent lamps and TV screens give the Thingamagoops a harsher tone while natural and incandescent light produce a cleaner one.

Just like any analog synthesizer, the thing-a-ma-s have another oscillator that effects some variable. This is usually called a modulator or LFO. Here the modulator's waveform is pretty close to a square wave.

$100 ducks for VCO Synth Fun! Check the video on the jump...