The stereo field, by ear

• The stereo field against what a person hears (Plan 0194 Phase 6). Every number behind balance and spread was measured on synthetic stimuli, where the answer is known by construction; nothing yet says the quantity tracks what a listener hears. With the standalone capturing loopback and a preset binding balance to an obvious visual move — a horizontal offset or a hue — report (a) a track with clear stereo movement moves the picture the way it sounds, (b) a mono or near-mono track sits visibly still rather than wandering, which is the absolute quantity’s whole point (ADR-0215), and (c) the observed real-world min/mean/max of balance and spread over a few tracks. (c) is the deliverable, not the check: the range is written back into Expression language so authors calibrate a gain against a measurement instead of a guess — the same reason the band levels are published. The design expects real music well inside ±0.3; a much wider or much narrower reading is worth reporting either way. - RUN 2026-09-19 — balance tracks what a person hears; both (a) and (b) pass. Standalone on loopback, AMD iGPU dev box, against two throwaway probes: a bare readout (pan_x = balance, pan_y = spread, long trail, so a phrase paints a cloud) and a shipped look re-bound so balance walks a two-sided palette — blue at hard left, cream centred, red at hard right — with spread opening the figure. (a) Pass, a track with obvious stereo movement moves the picture the way it sounds. (b) Pass, a mono source sits visibly still. (c) measured through --audio on three 60 s clips plus a mono downmix as a control, ~5 100 hops each; the table and the three readings that come off it are now in Expression language. Two of those readings correct the prose this row was written against: the mean sits within 0.03 of centre while single hops reach ±0.4..±0.6, so ±0.3 describes the average and not the excursions; and spread averages 0.16..0.33 even on wide material rather than hovering near 0.5. A hard pan carries no spread at all, so the two quantities are independent and a preset must not gate colour on spread.