A real-time sonification of the lunar surface, read crater by crater.
The Earth-facing hemisphere of the Moon carries roughly one and a quarter million catalogued impact craters — some of them small enough to fit inside a city block, some large enough to hold one. Selenography reads them. A small instrument crosses the disc at a deliberate pace; each catalogued feature inside its window is struck as it passes, a single crystalline event in A Dorian, deterministic on the crater's diameter, latitude, age, and the basalt or highland beneath it. The piece is meant to play for hours. It never repeats.
The work was conceived for the gallery: a large-screen Moon viewed across a room, low frequencies carried by capable speakers, long reverberant tails. It is also intended to function at home, on headphones, as a stable accompaniment to other work.
Audio is generated in the browser, in A Dorian. A quiet four-voice drone at A2 / E3 / A3 / E4 carries the harmonic floor, with a high crystalline wash on the sixth, ninth, and twelfth harmonics breathing on slow LFOs of fifty-three, seventy-one, and eighty-nine seconds. Above the bed, every strike lands on a Dorian degree drawn from the crater's parameters — diameter sets the octave, latitude carries the melodic motion across the scale, degradation and a per-crater hash shimmer the pitch by a small amount in either direction.
Each strike speaks in one of six crystalline voices. Glint is a single long sine tone with a stretched-octave overtone — a struck wineglass. Knock is the same voice an octave lower, briefer and contained. Chime is a bell with five Dorian partials ringing together under a sub-third for inharmonic colour. Settle is one quiet midrange tone fading. Pebble is two crystalline taps a few degrees apart. Bowl is a singing-bowl tone — sub-fundamental, fifth, octave, and a high shimmer — that lets the body of the Moon ring; the largest, oldest features in the catalog land here.
The Moon fills the frame at the centre of the canvas. A cyan X / Y gantry traverses the visible hemisphere on a slow path that takes some seven minutes to cross from one limb to the other and roughly fifty minutes to complete a vertical cycle. Where the gantry rests, a translucent magenta square — sized to the audio scan window and tinted as a lens treatment over the lunar surface — marks the active region.
When a feature is struck, a small read-out floats into one of the viewport corners: a schematic of the crater drawn in vector lines — rim, inner-wall shadow, ejecta blanket, ray system for the freshest features, central peak where one would form, compass marks, and a scale bar showing the diameter in kilometres. The schematic refuses the photographic; what the audience sees is the data the piece is reading, rendered as drawing.
In its installation form, the crater stream drives an eight-channel CV output to a modular synthesiser instead of the browser engine.
Selenography joins an ongoing series of real-time sonifications that includes Sounding (Pacific Northwest tides), Ephemeris (low Earth orbit), Lightcurve (James Webb imagery), Helioscope (the Sun), and Phase Space (strange attractors).
Joshua Borsman makes sculpture, sound, and kinetic work — staged in galleries, gardens, sidewalks, and orbit. The pieces convert real, public signals — orbital trajectories, ocean tides, the protocols that hold the internet together — into work that unfolds in time and refuses to repeat. Documentation and other work at joshuaborsman.com.
The code, audio synthesis, visual artwork, and accompanying text are © 2026 Joshua Borsman. All rights reserved. NASA imagery and IAU nomenclature referenced by the work are in the public domain.
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