Additive synthesis builds a timbre by summing a fundamental with individually controllable harmonics

Additive synthesis constructs a sound from its spectral components rather than carving them out of a rich waveform (the subtractive approach). The Buchla Model 148 Harmonic Generator makes this concrete: it outputs a fundamental plus its first nine harmonics (harmonic numbers 1–10) simultaneously. Routed through mixers (106/107), gates (110), and attack generators (180), each partial can be independently mixed and enveloped, so the timbre’s spectrum evolves under programmed control — a bright attack that mellows as upper harmonics fade, for instance. This is the West-coast route to timbre: assemble the spectrum from parts, instead of subtracting from a complex source.

Examples

Model 148: ‘Generates a fundamental and its first nine harmonics (harmonic numbers 1-10)’ and is ‘frequently used in conjunction with mixers, gates, and attack generators to enable precise programmed envelope control of individual overtones.‘

Assessment

Define additive synthesis and explain how independently enveloping single harmonics differs sonically from putting one envelope on a complex waveform.