Diel

Diel is a sonic sundial. It plays one continuous generative chord, and every quality of what you hear and see — register, brightness, warmth, shimmer, the colour of the sky — is a pure deterministic function of the clock.

sky & sound = f( the current moment )

Nothing loops. Nothing is random in real time. Leave it open in a tab while you work and, over a few days, you pick up a perceptual skill that did not previously exist: telling the time by ear.

What is actually happening

Two clocks are braided together.

Solar time drives the readable arc. Brightness follows a sun curve — (1 − cos(2π·p)) / 2, where p is the fraction of the local day. It is dark and muffled at midnight (a ~120 Hz lowpass) and wide open and luminous at noon (~7 kHz). That single curve moves the filter, the register and the sky colour in lockstep.

The calendar date reseeds the day's musical identity — root, mode, voicing and name — from a date-keyed PRNG over a curated, always-consonant set. Today genuinely does not sound like yesterday, and everyone on Earth is hearing the same motif today.

Morning and afternoon share a brightness, so the rate of light breaks the tie: mornings rise cool and crystalline with a high-shelf lift, evenings fall warm and golden with the highs rolled off and the low body swelling. Dawn, noon, dusk and midnight are sculpted to be unmistakable, and you learn to feel the hours between them.

The one control

A 24-hour ring. Drag it and you scrub a whole day in about three seconds — sunrise to midnight as one continuous morph of sound and sky — then release and it eases back to the living present. Tap the centre to reveal the hour and check your guess. There is a companion page behind "what is this?" that explains the engine with the engine running underneath it.

Turn your sound on. Browsers need one click before audio starts, so Diel opens on a gate; click anywhere and the chord fades up over six seconds exactly where the day currently is.

How it was made

Built with Claude Code as a single self-contained HTML file: hand-written Web Audio with no Tone.js, 2D Canvas for the sky, zero dependencies, no network, no account. The reverb is a JS-generated impulse response and the limiter is a tanh soft-clip.

The two constraints that shaped it were perfect determinism — the same instant sounds identical on every device forever, so you could compute what Diel sounded like the morning you were born — and a guaranteed-beautiful floor: every daily seed is constrained to low roots and consonant modes with all pitches snapped to scale, so no date can ever sound harsh. Every parameter glides via setTargetAtTime and voices crossfade, so it is click-free, and the whole day was checked to stay well clear of clipping.

diel · adjective · of or belonging to a 24-hour day.