Katsushika Hokusai, Under the Wave off Kanagawa (c. 1831). The third playable painting, and the one built furthest for the couch: sweep your whole arm and the sea swells, raise your hand and the wave climbs, chop down and it breaks. Lean, and the whole sea leans with you. Everything settles back to the true print.
How to play — from the couch
Sweep your whole arm sideways — the sea swells.
Raise your hand high — the wave climbs.
Bring it down fast — the wave breaks.
Hold your palm still over Fuji, a boat, or the claw to play it.
Lean left or right — the whole sea leans with you.
Both arms up together — the biggest surge of all.
Camera is blocked for this site in this browser. To allow it: click the camera / lock icon at the left of the address bar → Site settings → Camera → Allow, then reload this page. In the Muse app's built-in page view the camera can't be passed through at all — open this page in Chrome instead. Sound-only play works fully either way.
Start turns on sound and the camera together — browsers require a tap first. This is the couch piece: whole-arm moves, and the sea answers big. Mouse and touch play everything too.
The Monet asked for fingertips and the Van Gogh for a circling hand. This one is played with your whole arm, from the couch — every gesture is a big one, and the print answers at full scale: a swell you build sweep by sweep until the wave breaks on its own, or you break it. Nothing is cut out of the print, and the water never blurs: it moves along the lines Hokusai actually drew — the curl turns the way the crest is breaking, the trough bands stream along their own length, Fuji and the sky hold perfectly still — and every movement settles back to the true print.
Three honest answers to what this print sounds like, all switchable above — and all three from the print's own tradition, because the music follows the artwork's culture: Japanese scales, Japanese instruments. Each changes the scale, the harmony and the instruments, not just a playlist — and none of them is a recording: the notes are generated live in your browser, in the manner of each world, so you are playing the print rather than playing along to a track.
IN SCALE (MIYAKO-BUSHI) · KOTO, RIN & TAIKO
The sound of Hokusai's own Edo. The miyako-bushi scale — with its two dropped, yearning semitones — is what the koto and shamisen of his city played. Your sweeps pour out koto plucks, Fuji rings a temple bell, and when the wave breaks a taiko drum answers. The home world for this print.
IN SCALE (MIYAKO-BUSHI) ON A · SHAKUHACHI & SOFT PADS
The bamboo flute of the honkyoku tradition: breath before tone, long notes whose vibrato blooms only as they are held. Tuned to the very same in scale as Miyako-bushi, a fourth higher — where the home world plucks, this one breathes, and the sea answers slowly. The calm, drifting behaviour of the old second world, kept; its tuning now comes from the print's own tradition.
YŌ SCALE · BELLS & SOFT PADS
The bright major-pentatonic yō scale — the same print on a windless morning. Everything is gentler here: bells instead of plucks, a softer drum when the wave breaks, longer spaces between the pads. Proof the sea in this print is weather, not fate.
Design follows the playable-painting research of 30 Oct 2026 and the series rule that came out of the first two pieces: the whole print is drawn underneath at all times, and every warp springs back to the true image within ~0.5–1.5 s — nothing is cut out, lifted off the surface, or left displaced. The renderer was rebuilt after the Starry Night revision's lessons — that carrying paint through a resampling buffer blurs the linework a little more every frame until flow reads as fuzz, and that rotating paint through a centre-peaked (Gaussian) profile shears strokes apart by the same route. Now each frame samples the full-resolution print exactly once (with anisotropic filtering where the driver offers it), at coordinates displaced along the print's own geometry, so Hokusai's strokes stay as sharp at full stir as at rest: every rotation — the curl around its painted centre in its breaking direction, a circling hand's swirl, the claw's flex, the boats' pitch — turns on a rigid-core profile, full angle across the core and feathered only at the rim, so whole strokes travel intact; the curl also winds slightly inward, like the painted spiral; the trough and second-wave bands stream along their diagonal length; the swell's heave runs along those same bands instead of generic sine wobble; and the whole flow is masked to the water by the print's skyline — Fuji, the sky, the cartouche and the signature are held perfectly still while the sea moves around them. Displacement is a pure function of a handful of state variables — swell energy, curl angle, lift, lean, stream pulse — each one a temporally smoothed leaky integral of gesture energy and direction; raw per-frame hand positions and velocities reach the image nowhere, so camera tracking noise cannot make the print tremble. At rest every state variable is exactly zero (decays snap to zero below a threshold rather than fading asymptotically), every time-driven term multiplies against zero, and the displayed frame is the untouched print, identical from frame to frame. Full screen fits the print to the screen's height — top and bottom flush, dark sides — so Fuji and the boats are never cropped. A soft foam-pale glow follows each tracked hand (and the pointer) so the player can see where their hands are; it is orientation only and never triggers anything. This third piece adds the couch specification the player asked for: gestures are read from the whole hand, arm and body rather than the fingertips (a sweep counts at roughly 40% of the camera frame, a raise or a chop at roughly a third, a feature is played by holding an open palm still over it — whole-hand targets, no fingertip aiming — and a lean reads as both hands travelling together as the body moves), motion is amplified about twofold between hand and water, and the responses are scaled up to match — a building swell, a climbing crest, a two-arm raise for the biggest surge, a lean that tilts the whole sea, and a breaker with spray, drum and bucking boats. Harmony is locked to one scale per sound world, so any two features played together harmonise. The audio graph is built so no sound can run away: the koto voice is rendered as decaying harmonic partials with a one-shot plectrum tick — an earlier version used a feedback delay line whose harmonics could pile up into a sustained screech, and that design is gone; every voice in every world is a bounded envelope with a scheduled stop, at most 24 voices sound at once (the oldest are faded out to make room), the continuous sea wash is gain-capped, and a compressor-limiter sits between the master gain and the output. Hand tracking uses MediaPipe Hands (full model, camera requested at 1280×720, detection and tracking confidence 0.5 — tuned for distance over precision) with the deliberate-gesture recipes the research took from Gesture Synth's shipping implementation — 55% per-frame landmark smoothing, and a held-still palm as the deliberate press — so crossing the print never fires a note. Honest range, for standing play backed up from the computer: palm tracking in a browser is a near-camera technology, and nothing here changes that. In practice, on a typical laptop or TV camera, expect held-palm taps to read reliably within roughly 1–2 metres; the big single-hand gestures — sweep, raise, chop, stir — read further, roughly 2–3 metres, because they follow the palm's travel rather than its detail, which is exactly why this piece is built from them; the two-hand gestures (both arms up, leaning) sit between, roughly 1.5–2.5 metres, because both palms have to stay tracked at once. Past about 3 metres, expect tracking to drop out rather than degrade gracefully — put the camera nearer the couch than the screen if you can; mouse and touch lose nothing. Spray and foam are the one drawn layer over the print: formed droplets with a bright bead and a pale-blue belly shadow, stretched along their flight, and clustered foam puffs that swell and thin as they fall back into the sea.
Image: Katsushika Hokusai (1760–1849), Under the Wave off Kanagawa (Kanagawa-oki Nami Ura), from Thirty-six Views of Mount Fuji, c. 1831. Polychrome woodblock print, ink and colour on paper, 25.7 × 37.9 cm. The Metropolitan Museum of Art, New York — H. O. Havemeyer Collection, Bequest of Mrs. H. O. Havemeyer, 1929 (accession JP1847). Scan via Wikimedia Commons, shipped here downscaled to 2048 px wide. The print is public domain; the Commons PD-Art position treats faithful reproductions as public domain in the US, with the caveat that other jurisdictions may restrict reuse. The waves are okinami — great offshore waves — not a tsunami, whatever the file name says. Debussy and the La mer cover: he owned a copy of the print and the wave appeared, adapted, on the cover of the first edition of the score (Durand, 1905). The miyako-bushi and yō scales are the two classical Japanese pentatonic modes; the music in those worlds is generated in their manner, not recorded.
