ZVEX shared this video, demonstrating the Candela Vibrophase – a sort of steampunk, candle-powered Leslie effect.
Here’s what they have to say about it:
The Candela Vibrophase is an audio guitar effect that produces a mono output which creates a realistic 3D rotary speaker effect combined with phasing, wah, vibrato and tremolo effects.
This hypnotic sound is produced using no batteries or power supply, merely a candle that drives two solar cells and a Stirling heat engine that spins an optical control disc whose design can be controlled by the user.
Zachary Vex says that this would cost about $6,000, but the savings in batteries would pay for it in about 2,000 years.