Synthesis Fundamentals

An oscillator is what generates sound in a synthesizer. It creates a repeating waveform at a specific frequency — that frequency is what we hear as pitch.

Different waveform shapes produce different sounds. Try each one below and listen to how they differ.

Why does a sawtooth wave sound brighter than a sine wave? It comes down to harmonics — additional frequencies above the fundamental pitch.

A sine wave is pure — just one frequency. A sawtooth wave contains the fundamental plus every harmonic above it, each getting quieter as they go higher.

You already know what a filter does. A coffee filter lets water through but blocks the grounds. Sunglasses filter out bright light. A filter separates what you want from what you don't.

Audio filters work the same way — they let some frequencies through while blocking others. A lowpass filter lets low frequencies pass through while blocking the highs. That's why synth sounds get "darker" as you close the filter — you're blocking more of the bright, high frequencies.

The cutoff frequency determines where the filter starts working. Resonance adds emphasis at the cutoff point, creating that classic "wah" character.

Different filter types let different frequencies through — and that's where they get their names. A lowpass filter lets low frequencies pass through (and blocks highs). A highpass filter lets high frequencies pass through (and blocks lows). A bandpass lets through only a narrow band of frequencies in the middle.

An envelope controls how a parameter changes over time when you play a note. The most common is ADSR: Attack, Decay, Sustain, Release.

Attack is how long it takes to reach full level. Decay is how long to fall to the sustain level. Sustain is the level held while the note is pressed. Release is how long to fade out after letting go.

Envelopes can control more than just volume. Apply an envelope to filter cutoff and your sound opens up as notes play. Apply it to pitch and you get plucks or laser effects.

An LFO (Low Frequency Oscillator) creates slow, repeating changes over time. Apply it to pitch and you get vibrato. Apply it to volume and you get tremolo. Apply it to filter cutoff and you get that classic wobble.

Rate controls how fast the LFO cycles. Slow rates create gentle movement. Fast rates create more aggressive effects. Depth controls how much the LFO affects its target.

Now you understand the building blocks. An oscillator generates the raw sound. A filter shapes its tone. Envelopes control how things change when you play notes. LFOs add ongoing movement.

Every synthesizer — no matter how complex — uses these same fundamental concepts.

Time to put your knowledge to work. Listen to a target sound and try to recreate it using what you've learned.