a coloring book you can hear
Hue Fourier is the coloring half of Slow Fourier. Its plates are drawn by mathematics — every one of them is a sum of circles — and every shape a plate encloses is a note. Fill a cell in and its note joins a chord. Color a whole plate and you've composed something, without composing anything.
Nothing is scored. There are no accounts. Nothing leaves your phone.
big shapes hum low, small shapes ring high
Slow Fourier turns the pen's distance from center into pitch. Hue Fourier applies the very same law to the shapes you fill: a large cell hums low, a small cell rings high, and every note is drawn from one five-note scale — so a plate can't be colored out of tune, no matter who's holding the crayon.
Each fill swells its note into the chord and lets it fade over a few breaths. Bigger cells are louder; tiny cells sparkle. Touch the wrong cell and ink takes it back: tap the dark dot beside the wheel, then tap the cell, and it is the page again. Undo steps back one cell at a time.
You're not decorating a picture. You're painting a sound.
nothing composed, everything compiled
When a page is done, make a song. The same compiler that turns a Slow Fourier drawing into a song reads your coloring by five printed rules: the cells become the melody, in the order you colored them; every cell you fill is a drumbeat; the loudest cells become the chords; your coloring pace sets the tempo; and the chorus is the same page, an octave up. You get the song, a process card that shows its working, and the recipe that would make it again, note for note.
The rules are printed in full at slowfour.com/compile. The page itself is never changed.
hue, then Fourier
A hue is a color's family name — red, gold, blue — before light or shade get involved. And Fourier is Joseph Fourier, the mathematician who showed, two centuries ago, that any curve can be built from circles turning at different speeds. Say the two words together and you'll hear the third word we hoped you'd hear.
Slow Fourier draws. Hue Fourier colors. Same circles, same math, two hands.
thirteen ways the math carves a page — new every day
The pages change at midnight (UTC), the same for everyone, everywhere. Each plate borrows a painter's register. Each is still, underneath, a sum of circles.
- Klee whimsical compartments from overlapping curves
- Mondrian blocks split on musical ratios — the tritone, the golden section
- Pollock an all-over field of hundreds of small cells
- Cathedral a rose window of rings, spokes, and petals
- Spirograph a guilloché rosette — literally circles on circles
- Kandinsky a grid of concentric-circle cells
- Op Art a grid swelling under a lens
- Girih an Islamic star tessellation — symmetry as harmony
- Art Nouveau whiplash panels with leaded jewels
- Interference two point-sources rippling into fringes
- Stella interlaced protractor arcs
- Miró a biomorphic field of blobs, a star, a crescent
- Escher interlocking tiles that mate edge to edge
the link is the recipe
When you share a coloring, you get a card — the plate, the chord it makes, and the note names you painted. But the link underneath isn't a picture. It carries the plate and the exact order you colored it, and replays it, cell by cell, for whoever opens it. Two people can color the same plate and share two different songs.
This card carries no audio — the link sings.
what did you notice?
What was quiet, what was loud, what broke. A person reads every one.
Nothing leaves your phone.
Every note is built and played on your own device. No accounts, no scores, no tracking. The only thing that travels is the recipe you choose to share.
z(t) = Σ ck e2πikt