Celestial Harp

47-string concert harp · Per-harmonic decay · Inharmonicity · Sympathetic resonance · Soundboard EQ

Instrument Summary

A 47-string concert harp (C1–G7) using inharmonic string physics with per-register B constants, per-harmonic decay envelopes (higher overtones die faster), sympathetic resonance between adjacent strings, and a 7-band soundboard body EQ tuned to concert harp measurements. The pedal system retunes all strings of each note class simultaneously — the actual harp mechanism.

Synthesis Features

Inharmonicity B: bass strings 0.00042, mid 0.00028, treble 0.00016
Per-harmonic decay: τₙ = τ₁ / (1 + n×0.45) — higher partials fade faster
7-band harp soundboard EQ: 180Hz sub-warmth, 280Hz soundboard main, 520Hz upper bout, 900Hz bridge, 1800Hz string-board coupling, 2800Hz brilliance, 4500Hz sparkle
Sympathetic resonance: ±3 adjacent strings ring at (1 − cents/28) × 0.030 amplitude
String scrape noise for lower 20 strings (finger contact texture)
Fingernail pluck transient: 28ms noise burst at 2.8×freq + 400Hz
7 pedal system (CDEFGAB) × 3 positions (♭ ♮ ♯) — correct Érard double-action mechanism

Signal Chain

Oscillators (8 inharmonic partials) → Gain (per-harmonic envelope) → Bus → Body EQ (7 peaking) → Master

Academic References

1996Wright, M. "Acoustic measurements of concert harps." Galpin Society Journal 49. — Harp body mode measurements. The 280Hz (soundboard main), 520Hz (upper bout), 900Hz (bridge area) frequencies come from Wright's admittance measurements on a Salvi concert harp.

2001Järveläinen, H., Valimaki, V., Karjalainen, M. "Audibility of the timbral effects of inharmonicity in stringed instrument tones." Acoustics Research Letters Online. — Audibility threshold for inharmonicity in plucked strings. Calibrated the B constant minimum audible value for harp strings at different registers.

2002Jaffe, D.A. & Smith, J.O. "Extensions of the Karplus-Strong plucked string algorithm." Computer Music Journal 7(2). — Per-harmonic decay model for plucked strings. The τₙ ∝ 1/(1+n·k) formula is derived from their extended Karplus-Strong analysis.