Imaginando's COLAPSO builds its partials from measured atomic emission lines

Most additive synths let you draw partials or derive them from a waveform. COLAPSO, which Imaginando released on 7 October, takes them from a physics database.

The source data is the measured emission spectra of 22 elements, 422 lines in total, cross-checked against the NIST Atomic Spectra Database. Each line becomes a partial. Its wavelength sets the partial’s frequency, its relative intensity sets the level, and its Einstein coefficient, the rate at which that transition happens, sets how long the partial lasts.

Forty octaves down

Light sits around forty octaves above the audio range, so the spectrum has to be transposed. COLAPSO keeps the intervals between an element’s lines and moves the whole set down until the strongest line lands on the key you press.

That has a consequence worth knowing before you play it. The strongest line is not necessarily the lowest, so some partials sit below the note you played and some above. The spacing between them follows the physics of the atom rather than a harmonic series, so the result is an inharmonic spectrum, closer in structure to a bell or a struck plate than to a sawtooth.

Decay times from the atom

In the atom, line lifetimes run from under a nanosecond to a few milliseconds. COLAPSO keeps their order but stretches them to between tens of milliseconds and several seconds. Strong lines tend to have short lifetimes, so the brightest partials die first and the spectrum keeps changing on a held note.

The main performance control, Observation, moves along the Gabor limit, the trade-off between knowing exactly when a sound happens and exactly what pitch it is. One end gives a broadband click, the other a stable tone.

Around that is a conventional synth: three oscillators per voice with up to 16 partials each, up to eight voices in Poly, Mono or Unison, nine filter circuits, four drawable LFOs, four drawable envelopes and more than 200 presets.

Price and formats

€69 until 1 November, then €89. It is also in Imaginando’s Synth Bundle with DRC and FRMS at €189, or rent-to-own at €8.90 a month. The demo has no time limit and every parameter enabled, with a short noise burst every 60 seconds and saving disabled.

VST, VST3, AU and standalone on macOS 13 or later (universal binary), and VST, VST3 and standalone on 64-bit Windows 10 or later. There is no mobile version.

Producer’s note

With partials below the played key, the pitch you hear may not be the note you pressed, and it can change as the strong lines decay. Check a patch against a sine at the same note before building a bassline or a chord part on it.