V0A (2026)

A monophonic pitch corrector built as three staged deliverables over one shared C++20 DSP library. V0A is an offline command-line renderer that takes a mono WAV, a manually specified period and pitch ratio, and writes a resampled WAV plus a diagnostic CSV. V0B adds automatic detection, octave arbitration, chromatic targeting, and voiced/unvoiced gating, still offline. V1-Lab wraps the same library in a JUCE AU/VST3 plugin with key, scale, retune speed, and a note matrix.

Correction runs through a period-synchronous variable-rate resampler. A fractional read head advances over a circular buffer; when read/write separation exceeds bounds, the read coordinate jumps by one detected period — subtracting a period to repeat a cycle when shifting sharp, adding one to delete a cycle when shifting flat.

The project reconstructs the behavior of Antares Auto-Tune EFX 3 clean-room, from public patents and forensic technical research, with no proprietary binaries or copied source. Decisions follow a fixed authority order: the product directive, then the architecture and evidence documents, then the research reports, then new engineering inference.

Every non-mechanical choice carries a provenance label: EVIDENCE-BASED for claims resting on the EFX 3 manual or the Hildebrand patent; PLAUSIBLE RECONSTRUCTION for inference consistent with the evidence; EXPERIMENTAL for testable hypotheses, disabled by default; and PRODUCT REQUIREMENT for project needs that make no historical claim.

The evidence ledger holds fifteen numbered claims, each with its classification and the engineering consequence that follows from it. A parallel registry holds sixteen hypotheses, each with a stable ID, a default state, and a discriminating test. Where the two research reports disagree, a table records each position and the decision implemented.

Measured plugin latency is 4,112 samples at 48kHz: the reconstruction’s own figure.