How Synthesizers Work: Oscillators, Filters & Envelopes
Build any sound from scratch with math
Build any sound from scratch with math
Every synthesizer sound starts with an oscillator that generates a repeating waveform. Different shapes create different timbres. Click each waveform to hear and see it.
Sine: pure tone, no harmonics. The simplest possible sound.
A filter removes frequencies from the oscillator's output. The most common is the low-pass filter, which lets low frequencies through and cuts the highs. Drag the cutoff to hear the brightness change.
Low-pass filter: frequencies above the cutoff are reduced.
The envelope controls how a sound changes over time. ADSR stands for Attack, Decay, Sustain, Release. It determines whether a note plucks, swells, fades, or cuts.
How fast the sound reaches full volume. Short = percussive (piano, drums). Long = swelling (strings, pads).
How fast it drops from peak to sustain level. Short decay + low sustain = plucky sound.
The volume while the key is held. Not a time, but a level. 100% = organ-like. 0% = percussion-like.
How long the sound fades after the key is released. Short = staccato. Long = ambient tail.
Every synthesizer follows the same basic signal path. Understanding this chain lets you design any sound from scratch.
A sawtooth oscillator through a low-pass filter with moderate resonance creates the classic analog synth lead. Used in every genre from the 1970s onward.
Square wave, low-pass filter with low cutoff, short attack, medium decay, moderate sustain. The foundation of electronic bass sounds.
Slow attack, high sustain, long release, gentle filter. Creates atmospheric, evolving textures that fill the background of a mix.
Fast attack, fast decay, zero sustain, short release. The envelope does all the work, creating guitar-like or harp-like tones from any waveform.
The Minimoog, released in 1970, was the first portable synthesizer. It had just 3 oscillators, 1 filter, and 2 envelopes. Despite its simplicity, it defined the sound of electronic music for decades and is still used today.
You've learned how synthesizers build sounds from raw waveforms, carve them with filters, and shape them over time with envelopes. Every synth sound you have ever heard was built with these same building blocks.
Every synth sound starts with an oscillator producing a raw waveform: sine, square, sawtooth, or triangle. Each has a distinct character.
A filter removes frequencies. Low-pass cuts the highs (warmer). High-pass cuts the lows (thinner). The cutoff frequency controls where the cut happens.
ADSR (Attack, Decay, Sustain, Release) controls how a sound evolves. Fast attack = punchy. Slow attack = swelling. Short release = staccato.
Oscillator + Filter + Envelope = a complete sound. Change any one parameter and the character transforms. Infinite possibilities from three building blocks.
Put your new knowledge into practice!