Sound Design & Synthesis
Everything you need to understand how a synthesizer works, starting at the oscillator and ending with five different ways of building a sound. No presets, no patch recipes, no lists of which knob does what.
Foundations finished by proving that a note is a stack of partials. This course is about controlling that stack, and the five synthesis methods in the second half are best read as five answers to one engineering question rather than as five separate subjects.
The derivation
Lessons 1 to 5 build a single subtractive instrument from nothing. Lesson 6 does the obvious thing instead, specifying every partial by hand, and finds out what that costs. Everything after it is a different escape from that cost.
- 01TimbreWhy two instruments playing the same note are obviously not the same sound.Establishes: A sound is a spectrum and an envelope, and the envelope matters more than anyone expects.
- 02OscillatorsThe classic waveforms, defined as spectra rather than shapes, and the arithmetic that makes a high note go wrong.Establishes: A waveform is its partial amplitudes. Partials above Nyquist fold back, so they must never be generated.
- 03FiltersCutoff, slope and resonance, read off the frequency response rather than off the knob.Establishes: A filter is a curve multiplied into a spectrum. Slope is poles, resonance is feedback.
- 04ModulationEnvelopes and LFOs are the same object at two different speeds, and that is not a metaphor.Establishes: Nothing is a control signal or an audio signal by nature, only by rate.
- 05A whole instrumentAssemble the last three lessons into something playable, then find out what a voice really is.Establishes: A synthesizer is a voice, allocated. Polyphony is bookkeeping.
- 06AdditiveBuild a spectrum the honest way: pay for every partial in it.Establishes: Total control, at a cost that motivates every method that follows.
- 07FMTwo oscillators, dozens of partials, and Bessel functions deciding how loud each one is.Establishes: A nonlinearity manufactures sidebands for almost nothing. Cheap, vast, and hard to steer.
- 08WavetablePrecompute the spectra, store them, and travel between them.Establishes: Trade memory for arithmetic, and band-limit per octave or lesson 2 comes back.
- 09Physical modellingStop describing the sound and simulate the object that would have made it.Establishes: A delay line is a length and a loop filter is damping. The spectrum is an output, not an input.
- 10GranularAbandon the frequency domain and build the sound out of fragments of time.Establishes: Below about fifty milliseconds, grains stop being events and fuse into timbre.
What this course is not
It is not a tour of any particular synthesizer, and it names no products. Every idea here is implemented in the page you are reading, in a few hundred lines of Web Audio, so that nothing has to be taken on trust and nothing depends on owning anything.
It is also not a sound design cookbook. There are no recipes for making a supersaw or a 909 kick. The bet is that someone who understands why a filter has a slope can derive the recipes, and that the reverse is not true.