How a Synthesizer Works
Every synth sound starts from three building blocks. An oscillator makes the raw wave: a pure sine, a soft triangle, a hollow square or a bright, buzzy sawtooth, each with its own overtone recipe. A low-pass filter carves away the highs, and sweeping its cutoff gives the classic "wow". An envelope (attack, decay, sustain, release) shapes the volume over time, turning the same wave into a soft pad or a short pluck. Along the way: Robert Moog's modular synthesizer (1964), Wendy Carlos's Switched-On Bach (1968) and the portable Minimoog (1970).
In this lesson you'll
- Recognise the four basic waveforms by ear and by their overtone recipes: sine (fundamental only), triangle (odd harmonics, 1/n²), square (odd harmonics, 1/n) and sawtooth (all harmonics, 1/n).
- Explain subtractive synthesis: a low-pass filter cuts the harmonics above its cutoff, a sweep of the cutoff makes the "wow", and resonance boosts the harmonics right at the cutoff.
- Read and design an ADSR envelope (attack, decay, sustain, release), and tell a pad (slow attack) from a pluck (fast attack, short decay) by ear.
Music in this lesson
- Switched-On Bach (album, named only)Wendy Carlos · 1968
Remember
The oscillator makes the raw wave, and each waveform is an overtone recipe: a sine is pure, a sawtooth has all the harmonics, square and triangle only the odd ones.
Subtractive synthesis means start rich, then carve away: the low-pass filter removes the highs above its cutoff, and sweeping the cutoff makes the sound say "wow".
The envelope shapes the volume over time: a slow attack gives a soft pad, a fast attack with a short decay gives a pluck. Real instruments work the same way: a piano starts fast, a violin can start slowly.