Pipe organs function as additive synthesizers by combining harmonics through stops.

Evidence

A pipe organ is one of the earliest forms of “additive synthesizer” for cre­ ating different sound timbres. In additive synthesis, the output sound is manipulated by means of adding harmonics together, and the stops of a pipe organ provide the means for this process. There are references to the existence of some form of pipe organ going back at least to 250 BC (Sumner, 1975). — David Howard, Jamie Angus, coustics and Psychoacoustics, 1551

Categorization

• DEFINE: Additive synthesis is concretely explained through the pipe organ, giving a tangible anchor for an otherwise abstract sound-design concept.
• SEED: The pipe organ as proto-synthesizer could anchor an essay on how ancient instruments prefigured modern digital sound design.
• corroborated: 2 independent passages support this claim — David Howard, Jamie Angus, coustics and Psychoacoustics, 1551