The road, split into colour. One line lies across the road, exactly like GRAVEL, and never moves by itself. What is new: the same strip is read four times at once. Brightness still drives what GRAVEL's line always drove — a crack is a short burst, a stripe across the whole road is a wide one with a thump, and a noise bed underneath rises and falls with how much the road is actually changing. But colour is a second, continuous signal alongside that, remixing the noise itself rather than triggering anything: how red the strip is drives Ring (a second, independently-filtered noise loop multiplying into the mix — noise ring-modulated by noise, never a note), how green it is drives Grit (the shared fold that eats the edges off everything), how blue it is sweeps the filter the noise bed sits behind. Ride past brick or a taillight and the ring rises; past hedges or a green door and the grit bites harder; under open sky or past a blue van and the bed brightens. There is no note anywhere in it, no scale, no clock, and not one oscillator — Ring and the bed's own filter carry a resonant hum for real body, but a crack and a stripe stay wide and broadband, so nothing here ever resolves into a pitch.

Tap the road to start, tap again to stop. Drag the handle on the right to move the line, or drag directly on the picture. Pinch to zoom, up to six times, a double tap gives the whole frame back. Swipe left for these few knobs, swipe right or Road to come back. Colour depth is the master rein on all three colours at once; the three arrows below it let you take any one of them further, or out entirely. Send it carries the whole set-up inside the link itself, nothing uploaded. Nothing is written on the server and nothing leaves this phone.

Named gaps: no recording, no film from your library yet — GRAVEL has both, this is the first cut of a new instrument and neither has landed here yet. Not yet ridden on an actual bike.