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Hybrid harp: KS pluck transient + pure additive sustain

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Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Kenneth Reitz
2026-03-29 16:20:49 -04:00
parent 237cfe171c
commit 6316a6c910
2 changed files with 17 additions and 4 deletions
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docs/_static/audio/synth_harp.wav
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pytheory/play.py
+17 -4
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@@ -828,10 +828,23 @@ def harp_wave(hz, peak=SAMPLE_PEAK, n_samples=SAMPLE_RATE):
phase = rng.uniform(0, 2 * numpy.pi)
wave += amp * numpy.sin(2 * numpy.pi * f_n * t + phase) * h_decay
# Soft finger pluck transient
pluck_len = min(int(SAMPLE_RATE * 0.006), n_samples)
pluck = numpy.sin(2 * numpy.pi * hz * 2.5 * numpy.arange(pluck_len, dtype=numpy.float64) / SAMPLE_RATE)
pluck *= numpy.exp(-numpy.linspace(0, 15, pluck_len)) * 0.2
# Karplus-Strong pluck transient — just the first ~50ms
# Gives the finger-on-string attack, then the pure tone takes over
period = max(2, int(SAMPLE_RATE / hz))
ks_rng = numpy.random.default_rng(int(hz * 77) % 2**31)
ks_buf = ks_rng.uniform(-0.3, 0.3, period).astype(numpy.float64)
# Pre-filter for soft finger pluck
for _ in range(4):
for k in range(period - 1):
ks_buf[k] = 0.6 * ks_buf[k] + 0.4 * ks_buf[k + 1]
pluck_len = min(int(SAMPLE_RATE * 0.05), n_samples)
pluck = numpy.zeros(pluck_len, dtype=numpy.float64)
for i in range(pluck_len):
pluck[i] = ks_buf[i % period]
nxt = (i + 1) % period
ks_buf[i % period] = 0.5 * (ks_buf[i % period] + ks_buf[nxt])
# Fade the KS pluck out quickly so the pure tone takes over
pluck *= numpy.exp(-numpy.linspace(0, 8, pluck_len)) * 0.4
wave[:pluck_len] += pluck
mx = numpy.abs(wave).max()