Making Sounds With Light

Building electronic sounds with photoresistors

Curt Seiss
Jan 14, 2018 · 3 min read
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One of Curt’s hand-built electronic instruments. This one is built into the case of a discarded piece of antique test equipment

As a part of my music-making practice, I endeavor to build a variety electronic music devices, drone machines and synthesizers. The construction and operation of such machines adds so much understanding and interaction with the process of music creation, the value cannot be overstated. While I don’t use home-built synthesizers in everything I record, when employed they add a unique textural character and tonal quality that is hard to replicate with VSTs, samples or acoustic instruments. These machines are occasionally used as the protagonist / primary voice in a track, but most often relegated to tonal, drone or textural accompaniment, similar to the way in which Indian classical music utilizes the tanpura or the drone pipes of a bagpipe. The frustration and time-consumption of building one’s own instruments is balanced by the gratification of knowing the end-product is likely to be something wholly unique. I like to build them into old equipment that is destined for the landfill— I think they look great and it give me a chance to reuse some of the original circuitry.

The process of playing hand-made electronic instruments for music making involves turning knobs to tune pitches, flipping switches to activate and influence various parametric controls — and sometimes even waving one’s hands over the instrument to interact and influence the sound without actually touching it — as with light-dependent components called .

Photoresistors carry an extraordinary fascination for me, as they are a basic and inexpensive electronic component, but their behavior in a circuit is the stuff of science fiction. Photoresistors are just resistors (resistors are used to reduce current flow within parts of a circuit and are found in virtually every circuit in your life — the remote, the microwave, your computer, children’s toys, etc.) but photoresistors are . Meaning, the more light to which they are exposed, the less they resist the current. More light = more current (as you’ll see in the in the example video here, I am shining a flashlight on them). This behavior has a lot of practical applications, especially in electronic music instruments as regulating the flow of current is one of the many ways electronic instruments facilitate controlled musical expression.

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Another of Curt’s drone synthesizers built into the chasis of a television repairman’s CRT tester. This one is approximately the size of a guitar pedal.

There is a lot that can be said about building electronics for music, and just as much to be said about how engineers have used this technology in amazingly creative ways (unlike the most basic ways I do). But for now, here is an example of some electronic instruments I have built that respond to light. This video was shot during a session where I was simply rolling tape to capture drones and effects that will be edited into a library of sounds that will be used for track construction at a later date. The process of creating one’s own sound libraries will be subject of a future post, but for now notice how the sound is impacted when the synth gets hit with the flashlight. And fathom how amazing it is that light can be used as a physical medium by which the tools of music creation are handled and manipulated. Pretty crazy, huh?

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