Shellac sound archive · accession 78-211 · lateral cut
Groove — a voice carved into a spiral.
A ten-inch shellac disc holds sound the way a canyon holds a river — as shape. This is a working study of the lateral-cut groove: one spiral, thirty-two turns, a hummed air in D minor. The wiggle you can see is the waveform. Engage the horn and the page reads the carving itself; nothing sounds that isn’t drawn. And every pass wears it — the archive’s cruel arithmetic is on the metre.
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This deck draws its record with the canvas element, which your browser declined to provide. The disc, the groove and the horn all live in that drawing — the production notes describe what you would have heard.
One hummed air. 393,856 numbers. One spiral.
01
The wiggle is the sound
Emile Berliner’s gramophone cut sound sideways: the stylus swings left and right, and the groove wall it leaves is the pressure wave of the air, drawn in stone at a few thousandths of an inch.
Nothing above is metaphor. The disc is one Float32 array, 393,856 samples long. The same array bends the spiral, fills the glass, and — when you engage the horn — is read back sample by sample into sound. There is no hidden oscillator, no second copy. If you could scratch the drawing, you would scratch the tune.
02
Seventy-eight, more or less
“78” was always an approximation: a 3,600-rpm synchronous motor through a 46:1 reduction turns 78.26, and early machines wandered either side. This deck holds an even 78.0 — one revolution every 0.77 seconds.
A real ten-inch side winds two-hundred-odd turns and carries about three minutes; this study disc carries thirty-two turns, roughly twenty-five seconds, cut with an electrical-era band of about 50–6,000 Hz. One pressing flaw is included at a fixed angle — listen for the soft tick that returns once per revolution.
03
A medium that forgets
Shellac is mostly stone — mineral filler bound in insect resin — and the steel needles sold in tins were meant to be discarded after a single side. Every pass grinds the groove wall, and the finest wiggles go first.
Here the abrasion is real arithmetic: each pass blends every sample toward its neighbours, and the metre measures what the carving actually lost — ten replays cost this pressing about five decibels above 2 kHz, nearer eleven up at 5 kHz where the finest wiggles live. Once worn, an oxblood hairline in the glass remembers the cut as it was on day one. To hear the record is, a little, to erase it.