Turning the Wheel by Fifths: A Colour Codex for Pitch

This paper publishes the colour codex that governs Arnaud Quercy's paintings, and fixes it as version 1.0: a stipulated rule assigning a colour to each note of the eighty-eight-key piano keyboard. Hue follows the cycle of fifths, with C as red and each fifth turning the colour circle one step; value follows register, with middle C at full strength, the lower registers darkening until every note merges into black, and everything white from C7 upward. The rule originated in a wind player's practice: the clarinet's twelfth, then an attempt to read saxophone transposition at sight through colour, which failed within a month because the reader is colour blind. The codex inverts that failed direction: music, which the painter masters, governs colour, which his eye cannot verify. After a proto-codex phase in 2022 and 2023, the rule was stabilised in 2024. The paper describes how the rule maps intervals onto the circle (fifths and fourths as neighbouring colours, thirds at a signing distance, the tritone as complementary opposition, the semitone as an uneasy near-opposition) and states what lies outside it: chords and gesture belong to composition. It corrects the description of the codex given in PUB-PAP0004, which presented it as a rule on tonalities, supplies the reference that paper's measurement device requires, and completes the chain of the field-material codices by giving their pitches a colour. The codex claims no perceptual truth; it claims only to be complete, fixed, and checkable.