[YueyuHoshizora]

Requested by 小語 · project thread

Summary

Dynamic pitch (src/core/synth.ts, renderVoice). While a voice glides, follows a pitch envelope or ramps ratios/fixed Hz, the old code ran 2 **, pitchAt, pitchEnvelopeAt and two rampAt per operator on every oversampled substep. Now:

• The pitch exponent e = glide/12 + envelope/1200 is piecewise linear, so it is evaluated at both ends of the output frame and stepped multiplicatively: 2^e(n + s/O) = 2^e(n) · r^s, r = 2^((e(n+1) − e(n))/O). That is two pows per frame (one when the exponent is flat).
• Ramped Hz is linear, or quadratic while a Hz ramp chases a ratio ramp. The parabola through x = 0, ½, 1 (hz = h0 + x(b + cx)) is exact in both cases. A first version with linear interpolation failed the Fourier phase-reference test in engine-v6.test.ts (2e-6 error), so the quadratic is required.
• Only a frame that holds a segment corner is smoothed, over that single frame.
• The duplicated ratio/Hz ramp code is now in one rampedFrequency helper.

Chorus (src/core/fx.ts). The four voices are π/2 apart and the right tap leads by π/2, so one sin/cos pair gives all eight taps: left [s, c, −s, −c], right [c, −s, −c, s]. Voices whose weight is exactly 0 skip their delay reads, and their contribution is exactly zero anyway.

The LFO was already evaluated once per output frame, so it is unchanged.

Output equivalence (vs main, 8 voices, 2000 blocks × 128 frames, 48 kHz)

Scenario	Max abs diff
chorus with 1/2/4 voices	0 (bit-identical)
ratio ramps, fixed-Hz + ratio ramps, pitch envelope, static	0 (bit-identical)
glide, standard / high	3.7e-9 / 3.0e-8: isolated 1-ULP Float32 rounding flips (−147 dB re peak)

Benchmark (5 interleaved base/new process pairs, median of per-block medians)

Scenario	main (ms/block)	this PR	Δ
glide, standard	0.737	0.644	−12.6%
glide, high	1.300	1.027	−21.0%
pitch envelope	0.723	0.640	−11.6%
ratio ramps	0.667	0.638	−4.2%
fixed-Hz + ratio ramps	0.689	0.639	−7.4%
static (no dynamic pitch)	0.475	0.471	noise
chorus 2 voices (default)	0.0372	0.0253	−32%
chorus 4 voices	0.0376	0.0274	−27%

Checks

• npm run typecheck: pass
• npm test: 443/443 pass
• npm run sound-quality: passed
• npm run security: passed
• dist/ rebuilt with npm run build

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-21T20:02:30.538911Z	b538ef2	PR opened
🔒 Security Review	✅ Completed 2026-10-21T20:04:57.613544Z	b538ef2	PR opened

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