An oscillator is the part of a synth that makes the raw tone, the starting sound before anything else shapes it. It produces a repeating waveform at the pitch of the note you play, and the shape of that wave sets the basic character you then filter, level and move. Get the oscillator and its waveforms straight and the rest of the synth has something to work on.
The idea applies to any synth or plugin, in any DAW or a browser instrument. Waveforms and detuning mean the same thing wherever you meet them. None of this is tied to one product.
An oscillator is the part of a synth that generates the raw tone, the starting sound before anything shapes it. It produces a repeating waveform, a shape that repeats over and over many times a second, and the speed of that repetition is the pitch, or frequency, of the note. Play a higher note and the wave repeats faster; play a lower note and it repeats more slowly. On its own an oscillator is just a plain, continuous tone, and almost everything else on a synth exists to shape what it makes.
The oscillator sits right at the start of the signal path. After it comes a filter to shape the tone and an amplifier to set the level, so the oscillator is the source that the rest of the synth works on. If you want to see where it fits in the whole chain, our guide on what a synthesizer is lays it out from start to finish.
An oscillator can be analog, generating its waveform as a continuous electrical signal, or digital, calculating the same shape as a stream of numbers. Both aim at the same waveforms, and while people argue about the character of each, the difference tends to be subtle next to the choice of waveform itself.
Each waveform has its own character because of the harmonics it contains, the quieter tones stacked above the main pitch. A sine is pure and plain; a sawtooth is bright and full; a square is hollow and reedy. The shape of the wave is the first thing that decides whether a sound is smooth or buzzy, before any filter touches it. These are the waveforms almost every oscillator offers:
| Waveform | Character | Often used for |
|---|---|---|
| Sine | The purest tone, a single frequency with no harmonics at all. Smooth, round and a little hollow. | Sub bass, soft bell tones, adding weight beneath other sounds |
| Triangle | Soft and mellow with only a few faint harmonics, a touch brighter than a sine. | Gentle leads, flute-like and hollow tones |
| Sawtooth | Bright and full, containing every harmonic, which makes it the richest raw wave to filter down. | Strings, brass, big pads and fat basses; the classic synth workhorse |
| Square | Hollow and woody, containing only odd harmonics, with a clear reedy edge. | Clarinet-like tones, retro game leads, plucky basses |
| Pulse | A square whose width you can adjust, which thins it out and makes it more nasal and reedy. | Narrow, reedy leads; gentle movement when the width is slowly modulated |
| Noise | No pitch at all, every frequency at once, like static or wind. | Percussion, hi-hats, wind and texture, the breath in a sound |
Many oscillators let you blend or switch between these, and some add more unusual shapes as well. The clearest way to learn them is to solo one oscillator, open the filter fully, and play each waveform in turn so you hear the raw difference before anything else shapes it.
Synths often run two or more oscillators together because layering them makes a bigger, thicker sound than one can give on its own. A single waveform is quite a pure, thin thing; stacking a second or a third fills it out. The two most common tricks are detuning and octave stacking.
Set two oscillators to the same note but tune one very slightly sharp or flat of the other, and the small clash between them makes the tone shimmer and move on its own. This is called detuning, and it is where a great deal of the width and richness in synth pads and leads comes from. A little detune sounds lush; a lot sounds broad and out of tune, so it is usually kept gentle. Some oscillators build this in as a supersaw, stacking several detuned sawtooth copies at once for an instantly wide sound.
A sub oscillator is an extra oscillator tuned an octave below the main one, usually a plain sine or square. You often do not hear it as a separate note; instead it adds low-end weight and power underneath, which is why it turns up so often in bass and lead sounds that need to feel solid. It is the quiet foundation more than a voice of its own.
Running more oscillators uses more of a synth's power and can muddy a sound if you overdo it, so two or three well-tuned layers usually go further than a large pile of them.
On their own, oscillators only supply the raw tone; the filter, amplifier and envelopes that follow do most of the shaping. But oscillators can also act on each other to create tones that a single wave cannot reach, and these interactions are worth knowing by name:
These are optional tools rather than everyday settings, and not every synth offers all of them. Most sounds you make will use plain waveforms and a touch of detune long before they need any of this.
Whatever waveform an oscillator produces, and however many you stack, the sound is still only raw material at this stage. What turns it into a finished tone is the filter that shapes it and the envelope that moves it over the life of a note. The oscillator decides the ingredients; the rest of the synth does the cooking.
Waveforms and detuning click into place far faster when you can hear them next to each other while a sound is playing. Reading the theory gets you the map; hearing it is what makes it stick.
ARGISH is a self-playing synthesizer. It builds its sound from oscillators like the ones this guide describes, and because it plays itself you can hear that raw tone become music rather than only read about it. Set a mood and a key, build a progression on the chord wheel, and it composes and evolves in the background while you turn knobs and hear what they change. It runs in your browser, or as a plugin in your DAW: an Audio Unit, a VST3, an AAX for Pro Tools and a standalone app.
You can hear it free in your browser first, no install and no account, then decide.
Everything on this page also works by hand on almost any synth, which is rather the point of writing it down.
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