The device on the right is a Thingamagoop — a simple handmade electronic synthesizer made by Bleep Labs. Unlike the synths you see at music stores, it’s controlled not by a keyboard, but by a photocell. The more light the photocell receives, the higher the pitch of the sound it emits.
If the design of the Thingamagoop looks familiar, it’s because it’s done by the fine folks at Goopymart.
The knob acts as a frequency control. One of the switches determines whether the Thingamagoop emits high or low sounds, while the other determines whether the sound output is continuous or switching on and off.
That dangling thing with a light? That’s the LEDacle (Light-Emitting Diode tenACLE), which you can move to affect the sound produced by the Thingamagoop. Its blinking is affected by the controls, and you can point its light at the photocell to change the pitch.
Thingamagoops have built-in speakers and a 1/4″ jack so that you can route its output to an amplifier or through effects boxes.
My only complaint about these beauties: the price is a little steep — it sells for $100. Perhaps Make magazine will do a piece on building your own.