#SynthSaturday 2/

What are #AnalogSynths? This is one of those simple questions that people argue endlessly about, but generally, any synth that doesn’t generate audio with a digital-analog converter could be considered “analog.”

More specifically, what most people mean when they talk about analog synths are subtractive synths. Not all analog synths are subtractive, and not all subtractive synths are analog, but the overlap is so massive that the terms get used synonymously.

#SynthSaturday 3/

So, uh… what’s a subtractive synth then?

The name is good hint!

Basically, you start with a harmonically-rich audio source. On an #analogSynth, this is usually a #VCO (which stands for voltage-controlled oscillator).

Then you subtract some of those harmonics. On an analog synth, you do this with a #VCF (voltage-controlled filter). By changing the frequency of the filter over time, you get sonically interesting results.

#SynthSaturday 4/

Musicians might have an idea what I mean when I talk about harmonics. But if that explanation kinda lost you, there’s an easy way to demonstrate.

Open your mouth wide and say “AAAAAA.”

Now slowly close your lips, so the sound goes kinda like so: “AAAAOOOOWWWW.” Maybe even go back and forth. “AAAOOOWWWOOOAAA.”

(Hopefully you’re reading this in a public place and now garnering some strange looks.)

#SynthSaturday 5/

The “AAAA” is a harmonically-rich sound. Even if you sing it at a relatively low pitch, there’s high frequency content in the sound.

And as you close your mouth and go to “OOOOWWWW,” you progressively carve away some of that higher frequency content without changing the pitch of your voice. Your mouth is acting like a #VCF here, specifically a low-pass filter (meaning it cuts high frequencies while allowing lower frequencies to pass).

#SynthSaturday 6/

(Fun fact: there are #synthesizer filters that are designed to mimic how the human mouth forms vowel sounds! These are called “formant filters.”)

#SynthSaturday 7/

Let’s go back to VCOs.

An analog oscillator makes a single note—technically an electrical waveform at a specific frequency. It might be able to make more than one wave shape, but they’ll be exactly the same frequency or a perfect division/multiple because it’s all originating from the same oscillation circuit.

The most common analog wave shapes are square and saw, followed closely by triangle and sine. (See image for examples of what they look like.)

#SynthSaturday 8/

By some neat synchronicity of sound and circuits and physics, saw waves and square waves are some of the easiest wave shapes to produce with analog circuitry, and also some of the most musically useful waveforms. The technical reason for this goes into more discussion of harmonics…

But thinking about how, say, a bowed cello string moves is a cool way to visualize why a saw wave is useful.

#SynthSaturday 9/

When a musician pulls a bow across a cello string, there’s some friction between them. The bowstring pulls the cello string…until the tension grows too great and the string snaps back, at which point it’s pulled by the bow again…and this cycle happening very quickly produces audible vibrations: the sound of a cello.

That motion—stretching then snapping back quickly—can be loosely visualized…as a saw wave!

#SynthSaturday 10/

A bowed string instrument doesn’t sound exactly like a saw wave, which is “buzzier,” because it’s the result of interactions between physical materials that soften the “saw” motion and change the harmonic content. But there’s a definite similarity.

And that’s where filters come in. A low-pass filter can take some of the “buzz” out of a saw wave, which brings it closer to the sound of a string instrument.

#SynthSaturday 11/

But where filters *really* shine is when they change frequency over time. And again, this is something that you can observe in acoustic instruments.

This time imagine the sound of a guitar string being plucked. 🎶twaanggggg🎶

Right after plucking it, the “twa,” the sound has more harmonic content. Then, as the sound decays, the higher-frequency overtones die away and the “anggggg” part of the sound has a more pure tone.

#SynthSaturday 12/

> the higher-frequency overtones die away and the “anggggg” part of the sound has a more pure tone

🤔 Well that sounds a lot like what a low pass filter does!

For a “pluck” sound, you’ll often set the VCF to pass more high frequencies initially, and then change the frequency of the VCF over time to cut more and more of those high frequencies.

#SynthSaturday 13/

Of course, there’s more to #synthesis than replicating acoustic instruments, but knowing the basics of how to produce similar sounds also gives you a better idea how to produce weirder, more alien sounds 👽👾🤖👹😈

VCOs and VCFs are barely even half the story when it comes to #AnalogSynths, but they’re the foundational building blocks to analog #SubtractiveSynthesis. Everything else hangs off this.

Buuuut this is long enough for now. So I’ll save that for next thread!