Each wave is one note: hue is its pitch class, lightness its pitch, from the palettecore pitch-colour helix — the colour rolls in with the crest and the tone sounds when the wave breaks. The driftwood on the sand is the 10 000-point study by @yuruyurau, beached here as the control: it has no pitch, so it takes no colour. The mapping is a designed convention (Newton and Scriabin disagreed about C); the audit of these exact colours is in output/waves_to_shore.json.