Oscillation of Oscillators


Salutations synth seekers! Last time, we discussed a brief history and overview of analog synthesis.

Additionally, I left everyone with two major points that will act as the bedrock for all topics moving forward:

1. Everything is made of waves.
2. Anything can be a source OR a destination.

While that’s all well, swell, and good, it won’t help us at all until we have some basic sounds to work with.

To do so, we should briefly discuss the nature of sound. Most of us learned in school about how sound is made of vibrations in the air and our ears picking up on those vibrations via changes in air pressure.

One term that I’ve noticed doesn’t get used as often is oscillation. An oscillation is a movement back and forth at a regular interval. In sound, those oscillations are the vibrations that we just mentioned. It could be the oscillation of a guitar string vibrating back and forth after being strummed; it could be the oscillation of a drum head after being struck by a stick; it could be the oscillation of your own vocal chords when you sing your personal tribute to the glory of synthesizers.

In an analog synthesizer, we will always find at least one oscillator as the catalyst for creating basic pitches. Many synthesizers have two or three oscillators, so you can create chords (multiple pitches sounding at the same time) or use those oscillators as other sources for modulation (this will be covered later on).

These oscillators have a voltage that is translated to a certain pitch. The higher the voltage, the higher the pitch and vice versa.

Some synthesizers, like my Minimoog Voyager pictured at the top of this page, can actually generate such a low voltage that the pitch becomes subsonic – meaning that human ears can’t perceive it. I’ll use this concept later on to demonstrate how the increasing oscillations lead to higher (and perceivable pitches), but I believe I can provide a more clear example using a metronome app.

The metronome on my phone far exceeds what most metronomes can do, and one of those items is that it can click so quickly that it winds up generating a pitch.

Imagine that as I increase the speed of the metronome, I’m really increasing the voltage of an oscillator on a synth.

You’ll notice that the clicks became so fast, they essentially “blurred” into a perceivable note. The same thing happens as we move from the subsonic to the sonic, but unless you’re a superhuman with super ears, an audio example of that wouldn’t carry the same meaning.

To put the velocity of this blurred speed into perspective, middle C (the note most of us learn first in the world of piano) vibrates about 261 times every second. That would be the same as hearing 261 of those clicks on that metronome app in a single second!

Lastly, regarding most synths, the oscillators have a few parameters that can be modified to change the sound:

1. Frequency
2. Octave
3. Waveform

The frequency is often a knob that allows you to shift the pitch up or down by a certain amount of steps (C to C# to D to D#, etc.). On my Moog, you can shift up or down each oscillator by a sixth (C to A as an example).

This can be used to generate chords, create a detuned (out of tune) sound, or many other items that will come into play in the coming weeks.

However, if you want to explore a larger range of pitches, you can incorporate the octave knob. This allows you to quickly jump a octave (C to C up or down) or more with a single action.

The range of octaves varies from synth to synth. Moog has always loved to push the envelope in this regard, so the Voyager can go through six octaves per oscillators. They are marked: 32′ 16′ 8′ 4′ 2′ 1′.

These marks are in reference to the pipes of a pipe organ. If you start with a pitch from a gigantic 32 foot pipe and cut it in half, you’ll get a pitch that’s twice as high (one octave) through a pipe that’s half as long. This process continues all the way to a one foot pipe.

Now that we’ve established what oscillators are, how they work, and how to get different pitches from them, we arrive at the waveform knob. This is a much deeper concept than just adjusting the frequency or octave, so it will be the topic of discussion next time.

Hopefully, you feel a bit more clear on the general idea of oscillation and how that concept has led to oscillators being the main generators of pitch in the synthesis world!