Subtractive synthesis creates new sounds by filtering harmonics out of a rich waveform

The defining move of subtractive synthesis is to start from a harmonically rich source and remove content: you use a filter to subtract harmonics, thereby creating a new waveform and thus a new sound. Because a sawtooth or pulse already contains many harmonics, sweeping a filter across it carves the spectrum into countless timbres from one oscillator. This ‘start rich, take away’ strategy is the opposite of additive synthesis (start from nothing, add sines) and is why the filter, not the oscillator, is the expressive heart of a subtractive synth.

Examples

A low-pass filter sweeping down a sawtooth turns a bright buzz into a soft, dark tone as upper harmonics are removed.

Assessment

Define subtractive synthesis in terms of harmonics and filtering, and contrast it with additive synthesis.