Subtractive synthesis is the most common method of creating sounds on a synthesizer, and it works by starting with a harmonically rich waveform and then “subtracting” frequencies with a filter until you get the tone you want. If you are new to sound design, subtractive synthesis is the best place to start because its signal flow is intuitive: you can hear exactly what each control does.
This guide explains the building blocks and then walks you through making a simple sound, so the controls on any synth start to make sense.
How subtractive synthesis works
The name says it all: you begin with more harmonic content than you need, then remove what you do not want. The classic signal chain is:
- Oscillator generates a raw, harmonically rich waveform.
- Filter removes frequencies to shape brightness.
- Amplifier controls the volume over time.
Envelopes and LFOs then add movement to those stages. For the bigger picture of how synths are built, see our explainer on what a synthesizer is.
Step one: the oscillator
Oscillators produce the basic waveform. Each has a different harmonic character:
- Sawtooth — bright and buzzy, full of harmonics. Great for leads and basses.
- Square/pulse — hollow and reedy, good for woodwind-like and retro tones.
- Triangle — softer, with fewer harmonics.
- Sine — pure, no harmonics, ideal for sub bass.
Subtractive synths usually start with the brighter waveforms because there is more for the filter to work with.
Most synths give you more than one oscillator, and combining them is where the sound starts to feel rich. Detuning a second oscillator a few cents against the first creates the slow, shifting beating that makes a patch sound wide and analogue rather than thin and sterile. Stacking an oscillator one octave below adds weight; stacking a fifth or an octave above adds shimmer. Many synths also offer pulse-width modulation on the square wave, which slowly varies the width of the pulse to add the same kind of animated movement without needing a second oscillator at all. That wide, detuned-saw sound is the backbone of whole genres — it is exactly what you reach for when you make synthwave.
Step two: the filter
The filter is the heart of subtractive synthesis. The most common type is a low-pass filter, which lets low frequencies through and cuts the highs above its cutoff point. Lowering the cutoff darkens the sound; raising it brightens it. The resonance control emphasises frequencies right at the cutoff, adding bite or a vocal quality. Sweeping the filter cutoff is one of the most recognisable sounds in electronic music.
Low-pass is the workhorse, but it is worth knowing the other filter shapes you will meet. A high-pass filter does the opposite, removing low frequencies, which is useful for thinning out a bass so it does not clash with a kick. A band-pass filter keeps only a narrow band around the cutoff and throws away everything either side, giving a nasal, telephone-like character that sits well for plucks and effects. Filters also differ in slope, usually quoted as 12 dB or 24 dB per octave: a steeper 24 dB slope cuts more aggressively and sounds darker and more focused, while a gentler 12 dB slope leaves more of the upper harmonics in place for an airier result.
Step three: envelopes
Envelopes control how a parameter changes over the life of a note. The standard is the ADSR envelope — attack, decay, sustain, release. Applied to the amplifier, it shapes volume; applied to the filter, it shapes how brightness evolves. Our full ADSR envelope guide breaks down each stage in detail.
The single most expressive trick in subtractive synthesis is routing an envelope to the filter cutoff. A short attack and decay with low sustain makes the sound open bright and snap shut quickly, which is exactly how a plucked or percussive tone behaves. A slow attack on the same destination produces a pad that gradually blooms open as the note is held. The amount control, often labelled envelope depth, sets how far the cutoff travels — a small amount is subtle, a large amount turns every note into a dramatic sweep.
Step four: LFOs and modulation
An LFO (low-frequency oscillator) adds automatic, repeating movement — a wobble on the pitch (vibrato), a pulse on the volume (tremolo), or a sweep on the filter. LFOs are what stop synth sounds from feeling static. For a deeper look, read what is an LFO.
Building a simple patch
Try this on any subtractive synth to hear the parts working together:
- Select a sawtooth oscillator.
- Lower the low-pass filter cutoff until the sound is dark, then add a little resonance.
- Set a filter envelope with a quick attack and medium decay so the sound opens up then closes — an instant “pluck.”
- Add a slow LFO to the filter cutoff for gentle movement.
From there, experiment. Changing one control at a time is the fastest way to learn what each does.
Common mistakes to avoid
A few habits trip up almost everyone when they first start designing subtractive sounds:
- Cranking resonance too high. A little resonance adds character; a lot turns into a piercing whistle that can dominate a mix and even self-oscillate. Push it until you hear the bite, then back off.
- Leaving the filter wide open. If the cutoff is fully up, the filter is doing nothing and every patch sounds harsh and identical. The whole point of subtractive synthesis is that the filter is shaping the tone, so let it work.
- Forgetting the amp envelope. A clicky start or an abrupt cut-off is usually an amplitude envelope with too fast an attack or release. A few milliseconds of attack and release removes clicks without softening the sound noticeably.
- Stacking too many voices. Three or four detuned oscillators sound huge in isolation but turn to mush in a busy arrangement. Bigger is not always better once the part has to share space with everything else.
Using your synth sounds in a track
You play subtractive synth patches with a controller — see what a MIDI controller is — then sequence and balance them like any other part. The wider mixing and mastering hub covers fitting bright, filtered synth sounds into a full mix without harshness.
Frequently asked questions
Why is it called subtractive synthesis?
Because you start with a harmonically rich waveform and then subtract frequencies with a filter to shape the final tone, rather than building the sound up from simpler parts.
What is the most important control in subtractive synthesis?
The filter, especially the low-pass cutoff and resonance. It defines the brightness and character of the sound, and sweeping it is central to the subtractive sound.
Is subtractive synthesis good for beginners?
Yes. Its signal flow — oscillator, filter, amplifier — is intuitive, and each control has an audible effect, so it is the easiest method to learn sound design with.
How is subtractive synthesis different from additive or FM synthesis?
Additive synthesis builds a sound up by summing many simple sine waves, and FM synthesis creates harmonics by using one oscillator to modulate the pitch of another. Subtractive works the other way round: it starts with a waveform that already has plenty of harmonics and carves them away with a filter, which makes the cause and effect much easier to hear.
Can I do subtractive synthesis with software synths?
Absolutely. Almost every DAW ships with at least one subtractive-style virtual instrument, and there are plenty of excellent free synth VSTs built the same way. The controls map directly onto the oscillator, filter, envelope and LFO stages described above, so anything you learn on a plugin transfers straight to a physical synth.
