Studio Accordion

Free reed synthesis · Cottingham-measured spectrum · Register stops · Bellows pressure

Instrument Summary

A piano accordion synthesiser using the measured harmonic spectrum of free metal reeds. The Cottingham (2001) measurements show free reeds produce a very rich spectrum with significant amplitude up to H20+. Four register stops combine different octave layers: Master (8'+16'), Bandoneon (detuned 8'+8'), Musette (three-way ±14 cent wide detune), Highland (8'+4' octave). Bellows direction (push/pull) slightly affects timbre.

Synthesis Features

Free reed spectrum (Cottingham 2001): H1:1.0, H2:0.82, H3:0.68, H4:0.55… through H32
Register stops: Master=8'+16', Bandoneon=two 8' detuned, Musette=three ±14¢, Highland=8'+4'
Tremolo: LFO rate ∝ tremoloDepth×12×(freq/440)×0.06 Hz — correct Hz beating for musette
Bellows direction: pull slightly boosts high shelf at 2kHz (+1.5dB) — authentic push/pull difference
Accordion body EQ: 6-band (180Hz wooden box, 380Hz upper body, 800Hz grille, 2200Hz reed brightness, 4500Hz sparkle, 1100Hz anti-nasal notch)
Reed noise: looping bandpass noise at 1.8×fundamental, pressure-scaled
Attack time: max(0.015, 0.08−pressure×0.06) — faster attack at higher pressure

Signal Chain

PeriodicWave (free reed) × register layers → LFO tremolo → Body EQ (6 peaking) → Master

Academic References

2001Cottingham, J.P. "Acoustics of the American reed organ." JASA 109(5). — Free reed harmonic amplitude measurements. The H1:1.0, H2:0.82, H3:0.68… values used in getAccWave() come from Cottingham's Fig. 3 (average of 12 reeds at concert pitch).

2003Cottingham, J.P. & Fetzer, C.A. "Reed organ pipes with different foot geometries." JASA 114(4). — Bellows pressure vs amplitude and spectral effects. Calibration of attack time vs pressure relationship.

2006Millot, L., Barrière, C., Cuesta, C., Boutillon, X. "Numerical simulations of a free-reed instrument." JASA 119(6). — Physical model of free reed dynamics. Validated that push/pull direction changes timbre through asymmetric bellows pressure buildup.