Fluid Sonata: Music Visualizer

Ten classical scores, each performed by a real fluid simulation over a live model of the solar system. Nothing is pre-rendered, and nothing leaves your phone.

A fluid simulation and a classical performance, both generated live on your phone, wired to the same clock.

There are no audio files in this app and no video. A piano is synthesized from scratch every time you press play — a fundamental plus four slightly sharp partials, a hammer thud on the attack, a small hall around it — and every note it plays is thrown into a real Navier-Stokes fluid solver running on the GPU. The left hand punches jets up from the floor. The right hand lands at an x position taken from its own pitch, so the melody plays the screen like a keyboard. Behind it all, a ten-body Newtonian integrator runs the actual solar system, on a real date.

TEN SCORES, FOURTEEN READINGS Seven pieces from the public-domain canon — Bach's Prelude in C, Mozart's Rondo alla Turca, Beethoven's Für Elise, Ode to Joy and the Moonlight Presto, Tchaikovsky's Trepak, Grieg's In the Hall of the Mountain King — plus three originals written for this app. Every score plays fourteen ways: piano recital, cathedral organ, strings, music box, jazz trio, electric guitar, synth, 8-bit, 16-bit, drums, deep bass, disco, techno and an EDM remix. Every instrument is synthesized from scratch — there is not one audio file in this app.

LISTEN TO THE ROOM Turn on Listen Mode and the fluid dances to whatever is playing near you — another app, a speaker, someone at a piano. The microphone reaches the analyser and nothing else: nothing is recorded, stored or sent, and turning it off releases the microphone.

TWO WAYS TO DRIVE IT ORBITAL Click puts everything on a circular touch surface — a thumb travelling around the ring moves the selection, with real detents you can feel and acceleration when you spin. Fluid Classic is a conventional dock and player. Pick either in Settings; everything is reachable from both.

STATIONS Three stations of music that is genuinely free to play, streamed from the Internet Archive: classical sides digitised by the Great 78 Project, and recordings Musopen commissioned and released for anyone to use. Every track earns its place by a rule that is checked when the list is built, not assumed.

PLAY YOUR OWN MUSIC Hand it any song on your device and the fluid dances to that instead. A live spectrum analysis drives the same choreography the written scores use. The file is decoded on your phone and never uploaded — the app has nowhere to send it.

RECORD THE STAGE Capture the fluid, the orrery and the music together, then save the clip to Files or Photos or send it straight on.

PRIVATE BY ARCHITECTURE, NOT BY POLICY No account. No analytics. No third-party SDKs. No tracking. Nothing you do here is collected. The app asks for one permission — the microphone, and only if you turn on Listen Mode. The whole engine ships inside the app, and the scores, your own songs and the simulation all run with the network switched off. Three things do reach out, and the app tells you which: a once-a-day check with Apple for a newer version, carrying nothing but the app's own identifier; StoreKit, to price the Full Concert; and — only when you choose a Station — the recording you asked for.

FREE FOREVER, AND A ONE-TIME UNLOCK Moonlight · Presto, Für Elise, the Classical reading and the EDM remix are free forever, with no time limit and no ads. The Full Concert unlocks the remaining scores and readings with a single purchase — no subscription, and it is shared with your family.

Also on iPad. Made by djEnterprises.