Recreating a bizarre century-old electronic instrument

There are a handful of instruments that are staples of modern music, like guitars and pianos. And then there are hundreds of other instruments that were invented throughout history and then fell into obscurity without much notice. The Luminaphone, invented by Harry Grindell Matthews and unveiled in 1925, is a particularly bizarre example. Few people have ever heard the Luminaphone and so Nick Bild recreated the unique instrument using modern technology.

The Luminaphone was a very early example of an electronic instrument and it worked by modulating the light shining onto a selenium cell, which is a kind of photoresistor. The signal output from that was then filtered and amplified, with the modulation rate creating a wave of a specific frequency — the desired note. It wasn’t possible at the time to turn a light source on and off fast enough for this purpose, so the Luminaphone used a spinning disc full of holes to modulate the light from an incandescent lamp. A simple key switch let the musician control power to that lamp to play a note. With several of those, modulated at different rates, it was possible to play polyphonic music.

Fortunately for Bild, today’s technology makes it possible to achieve a similar effect without so much hardware. His reinterpretation of the Luminaphone doesn’t feature a rotating element at all. It simply uses a laser pointed directly at a photoresistor that feeds a powered speaker.

An Arduino Nano 33 IoT board modulates the laser through a transistor. It can do that very quickly, replacing the rotating disc in the original design. Bild simply added a handful of buttons to control the modulation frequency of the laser. Pressing a button turns the laser on and off at a frequency matched to the corresponding note, such as 261Hz for middle C.

It sounds interesting, like an electronic organ effect on a digital keyboard from the ‘80s. And though it won’t revolutionize the music industry, it is really neat to hear this century-old concept.