OVERDRONE: SEE THE HARMONIC SERIES

Overdrone is a free, browser-based instrument that builds a drone from a single note’s overtones and shows them as light. Pick a starting note and up to 32 partials rise above it, each a whole-number multiple of the root. One partial sits at the centre of the sound while the others fade with distance from it, and the centre drifts through the series: climbing, falling, wandering, or tracing the primes.

Every partial is also a colour. Doubling a frequency keeps its pitch, so each tone is raised by whole octaves until it lands in visible light, between 395 and 790 THz. C2 at 65.41 Hz, raised 43 octaves, glows green at 521 nm. Its fifth partial becomes violet at 417 nm, and the seventh, the harmonic seventh, turns orange at 596 nm. Octaves share a colour, so partials 1, 2, 4, 8 and 16 all shine the same green. Cents show where nature parts ways with the piano: the seventh sits 31 cents flat, the eleventh almost exactly between two keys. You aren’t seeing invented colours. Every hue is a fact about where a note falls in its octave.

Make it your own

Choose any of 12 starting notes across five octaves, tuned to A = 440, 432 or 415. Send the centre along nine paths, including a pendulum, a random wander, the harmonic chord 4 5 6 7, a chain of pure fifths and the primes. Shifts land every half bar to eight bars, sweeping through the series or crossfading over a glide of up to 16 seconds. Shape the voice with falloff, root anchor, shimmer, chorus and stereo spread. Keep pure whole-number ratios or snap to equal temperament. Drag the filter pad to play cutoff and resonance, with every partial drawn as a coloured line, or let the filter track the centre partial as it moves. Add reverb from a small room to a 14-second void and a delay that follows the tempo. Start from six ready-made scenes, roll a random one, and save your own. Tap the prism beside the title to open a hidden drum machine, whose Partial voice strikes whichever overtone is at the centre.

See it move

The light field paints the series as it sounds, in five gradient styles: radial rings around the loudest partial, a turning conic wheel, a linear sweep, aurora curtains and prism bands. Glowing blooms swell with each partial’s volume, string modes trace the standing waves behind each overtone, and a spectrum strip tracks the centre as it travels. Go full screen and let it fill the room.

WHY LISTEN TO OVERTONES?

Every pitched sound, from a voice to a cello string, is a stack of these partials, heard as one note. Visible light spans just under one octave of frequency, so the octave-shifting that lets you hear the cosmos in Droning of the Spheres lets you see harmony here. It’s a modern take on an old idea: Newton split sunlight with a prism and matched its seven colours to the notes of a scale in his Opticks.