FLUID SONATA

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Just for Fun · djEnterprises

Fluid Sonata

A fluid simulation and a classical performance, both generated in this browser tab, wired to the same clock — over a live model of the solar system. Nothing here is pre-rendered: no audio files, no video, no libraries, and no fonts fetched at runtime. The only image the page loads is the djEnterprises mark.

What you're hearing

Ten scores — seven from the public-domain canon, three djEnterprises originals — played on a piano that is synthesized from scratch every time you press play — a fundamental plus four slightly sharp partials, each dying faster than the one below it, a hammer thud on the attack, and a small synthesized hall around it. The left hand plays the harmony: a rolled broken chord under Für Elise, hymn blocks under the Ode, bass octaves under the Presto.

Sound: EDM remix is the other reading of the same scores — the same notes over a four-on-the-floor kick, offbeat saw bass, detuned-saw lead, hats, claps and sidechain ducking. Switch any time with the Sound button, or press S.

• Bach — Prelude in C. BWV 846, the opening of The Well-Tempered Clavier, Book I (1722). The prelude is nothing but a broken chord turned over and over, so this plays that figuration over the prelude's harmony.
• Mozart — Rondo alla Turca. The third movement of the Piano Sonata No. 11 in A major, K. 331 (published 1784): four-note turns climbing, then a broken chord tumbling back down.
• Beethoven — Für Elise. Bagatelle No. 25 in A minor, WoO 59 (1810). Its sixteenths run at 126 BPM; the left hand rolls its chord over six of them, which is the piece's own 3/8 bar.
• Beethoven — Ode to Joy. The theme from the fourth movement of Symphony No. 9 in D minor, Op. 125 (1824), at 122 BPM, harmonised I–V like the hymn it became.
• Beethoven — Moonlight · Presto. Piano Sonata No. 14 in C♯ minor, Op. 27 No. 2 (1801), third movement: rising arpeggios in sixteenths over the movement's harmony.
• Tchaikovsky — Trepak. The Russian dance from The Nutcracker, Op. 71 (1892): stomping leaps for half the bar, then a scale run tumbling downhill over the dance's own harmony.
• Grieg — In the Hall of the Mountain King. From Peer Gynt, Op. 23 (1875) — the creeping theme, then its answer a fifth up, over timpani and strings.
• djEnterprises — Aether, Skybound & Halcyon. Three originals written for this page: a dark cinematic ostinato, a bright adventure fanfare, and a slow airy wash. They exist because film and pop scores by living composers are still under copyright — synthesizing the tune is still a use of the composition — so rather than borrow, we composed. Nothing to clear, nothing to take down.

The three figuration tracks (Bach, the Moonlight Presto, Trepak) are engines playing each piece's characteristic pattern over its harmony, not transcriptions of the printed score. The others carry the actual theme. Everything here is public domain, or ours.

Each score loops a 32-bar shape that gets read twice over: as dynamics on the piano (piano → mezzo forte → pianissimo → forte) and as an arrangement in the remix (filtered intro → drop → breakdown → second drop). The choreography thins out and swells along with it either way.

What you're seeing

The classic stable fluids method (Jos Stam, 1999) running on the GPU: semi-Lagrangian advection, vorticity confinement, a 20-iteration Jacobi pressure solve, then gradient subtraction for a divergence-free velocity field. Half-float double-buffered framebuffers, a 144² velocity grid and a 720² dye grid, with a soft tone curve and vignette in the display pass. It is an actual incompressible fluid, not a particle effect.

The backdrop

Those orbits behind the dye are not decoration: that is the SolarEclipse engine — the same ten-body Newtonian integrator from the other experiment in this lab, with real initial conditions and a real running date (bottom-left). The sun blooms on every beat.

Zoom it with the slider, a two-finger pinch on the stage, the scroll wheel, or −/+ — from inside Venus's orbit out past Neptune. Drive the planets from a quarter speed to eight times with [ and ], and put names on them with N. Zooming redraws the orbit rings by fast-forwarding the integrator, so a wide view really is thirty years of Newtonian motion.

How they stay in sync

The audio scheduler stamps every sound with an AudioContext time roughly 150 ms before it sounds. Each frame the render loop consumes whatever has come due and throws dye and force into the field: every left-hand bass note (or, in the remix, every kick) punches twin jets up from the floor, claps shear in from the walls, hats sparkle at the ceiling, and every melody note lands at an x position mapped from its pitch — so the right hand plays the screen like a keyboard. The audio clock is the only clock; nothing musical is timed off performance.now().

The looks

Five palettes — Nocturne (the original), Aurora, Ember, Mono ink and Neon — and they rotate on their own every five seconds, each one changing hue mapping, force and how long the dye lingers. Press 1–5 to pin the one you like; the Look button hands the palette back to the rotation.

Controls

The fine print

Everything runs on your device. Nothing you do here is uploaded, and the page makes no network calls of its own — the only third-party request is djEnterprises' cookie-free analytics. Recording uses your browser's built-in WebM encoder and saves straight to your downloads; muting silences the recording too. The app needs WebGL and the Web Audio API, and it honors prefers-reduced-motion by cutting splat forces to 40% and switching the beat-brightness pulse off. On phones and low-core machines the dye grid starts one rung lower, and it drops again if frame times slip.

Share a setup by copying the URL — the current score and look ride along in the address bar.