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How to Make Sound Waves from Moonlight [1]

['Ethan Persoff']

Date: 2022-10-27

Hello and welcome back to Spoken Word with Electronics. This week we discuss the Moon. The silent glow-in-the-dark ball in the sky! The Moon is cool. Contrary to the Sun, you can stare at the Moon as long as you'd like. Staring at the Moon is even good for your mental health. (To make a pun on introspection, it is a source of reflective light, after all.) So this week we discuss how to convert Moonlight, which is heavily varied, shadow-casting, and subtle, into similarly variable voltage that can play synthesizers.

Items Needed

You will need a Moon:



For these instructions to work you will need access to Moonlight in some fashion. People living in cities or cloudy regions will have more of a challenge for this. If Moonlight is a rarity, perhaps this is something you can anticipate and schedule, or even take a road trip to a good Moon spot, using this recording method as a justification for the excursion. People who take solstices seriously might value this Moonlight World Map, as well. But fear not, Moonless folk! The included tutorial on track two includes instructions on equally good experiments, using household lamps, dimmers, and strobe lights. But, if you're specifically wanting to generate waveforms out of Moonlight, there's few ways around this: You need a Moon. Ideally a bright one.

Of course, some places have inadequate Moon coverage. Even on a cloudless night, light pollution might make your local Moon too dim or even unviewable. To address this, if you're in a small enough population, you can advocate to become a Dark Sky town. There's proof of this being successful and oddly politically even in terms of debate. Many varied opinions seem to agree on liking clear dark skies. Here in Texas, the city of Dripping Springs has achieved an Outside Lighting Ordinance to keep the lights off or dim. (Yes, lights are needed for safety, but not all bright night lights in a city are necessary) Who knows, maybe you can achieve something similar as a rewarding piece of eco-activism? The International Dark Sky Organization is a great place to start with resources and tips.

ADVISORY: Fake Moon fragments for sale on the Metaverse do not count as a real Moon. When in doubt of Moon authenticity, ask a frog.

In the audio for this episode we use Moonlight in track one. You'll hear it modulating the audio on a field recording of crickets and controlling numerous cascading parameters of the music underneath. I had two sensors, each on a cable, which I'll describe below.

I held the green cable (which is long, note how much it's been wound up) and wandered around, and laid the red cable on the ground. Here they are for reference:

Green Cable



Red Cable

The method of Moon Waveform Extraction (M.W.E.) that we'll be using is through use of Light Sensors to convert light into Control Voltage.

Light Sensors have a bunch of great names: Photocells, Photo Resistors, Photo Conductive Cells. With the equipment used in this exercise, the the Sensors will detect pure darkness as zero and a variation to the brightest of light at five. ( Advanced learning : They also provide a simultaneous flipped output, equal to negative five to zero.)

Cool word you've probably never heard of before. The method of light to voltage conversion you'll be using is called Optoelectronics!

As for sound created from this process, listen for a bell. A bell is generated by Moonlight hitting a leaf (captured by the green cable) which was bouncing in the wind so the bell was triggered in rhythm. Another ambient noise is generated by five minutes of Moonlight beaming down on some grass (red cable), triggered to a cloud floating over the Moon like a subtle filter.

The tools we'll use for this exercise are two eurorack modules: The Doepfer A-179-2 and the ADDAC ADDAC308:

Light to CV Modules Both of these modules do the exact same primary thing: They are both Light to Control Voltage modules. Neither of these modules make sound; rather they provide voltage to adjust other synthesizer modules. In this example, the Moonlight will shift in tone and hue and they'll track it and send positive and negative voltage out to another synthesizer module, making a hazy nice shifting ambience.

A Light to CV module works with sensors to convert a measurement of light into an output of measured voltage.

Basics: A completely dark light source (or absence of light) would mean no voltage output, while a completely bright light source would trigger an output of 100%. If you think of something as varied as light from the Moon during an evening, these variations can be extremely subtle, and both of these sensor modules allow for tuning the sensitivity, gain, and response of the sensors, allowing for a cascade of percentages of response. But they offer slightly different functions on how this voltage is processed and output; so I suggest they work best as a pair.

Let's compare them:

[END]
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