Insects as oscillators

Swarm Core plays recorded insects. Not synthesised chirps — actual field recordings of cicadas and crickets, from a dataset assembled for machine-learning research into automated species classification.

Why insects

Insect calls are already doing the thing a lot of synthesis tries to do and mostly fails at.

A cricket chorus is dozens of near-identical voices, slightly out of phase, slightly out of tune, arriving at slightly different times. That is the same problem as a massed-string wall — many voices, tuned against each other, read as one texture — except evolution solved it first and did it better. The individual calls stay individually audible while the whole reads as a single field. Most synthetic attempts at that either lock into obvious phase relationships or collapse into noise.

The other reason is that stridulation is not a clean oscillator. It is a mechanical scrape with a resonant body behind it, which gives it a spectral signature that is very hard to fake and instantly recognisable. It sounds organic because it is.

The bank

The samples come from InsectSet32 — cicadidae and orthoptera recordings, CC-BY 4.0. It was published as training data for automated acoustic species identification, not as a sample pack, which is exactly what makes it good: the recordings are clean, consistently captured, and chosen for their diagnostic clarity rather than for how they sit in a mix.

Swarm Core loads up to 64 of them, recursively, sorted. The SPECIMEN knob maps linearly across whatever is loaded, so sweeping it while triggering scrolls through the bank one recording at a time. It is a genuinely useful way to work — you audition by ear rather than by filename.

Two modes

Specimen fires one voice per trigger, pitched. Swarm fires up to eight, scattered in time by SCATTER, detuned against each other by DETUNE, across a fixed stereo spread. The pan positions are hard-coded and evenly distributed, which sounds like a limitation and is not: fixed positions mean the swarm has a stable spatial identity instead of smearing, and the scatter does the work of making it feel alive.

At low SCATTER the voices arrive together and phase-cancel into something that sounds like one large insect. At high SCATTER they spread far enough apart to read as a field of separate animals. The transition between those two states is the most interesting part of the module and it happens over about a third of the knob's travel.

Transposition is where it stops being a field recording

The PITCH range is ±24 semitones, which is a lot for sample playback, and that is the point.

Down two octaves, a cicada stops being a cicada. The stridulation rate drops below the point where it reads as a buzz and becomes an audible pulse train — you start hearing the individual scrapes as rhythm rather than as timbre. The resonant body of the insect, which at normal pitch sits somewhere in the upper mids, lands in the low mids and starts behaving like a formant.

What you get is not "a slowed-down insect". It is a completely different object that happens to have an extremely strange harmonic structure, because it inherited that structure from something that was never designed to make musical tone.

Up an octave it goes the other way and becomes almost pure texture — the pitch information disappears into a band of noise with structure in it.

Feed the V/OCT input from Harmonic Pressure and you get the same recording playing at eight harmonic partials simultaneously. That patch is the reason the module exists.

Two things that will confuse you

The bank loads on a background thread, so the module is silent for two to five seconds after you add it and the ACTIVE LED stays dark until it is ready. This is the correct behaviour — reading 64 WAV files from disk on the audio thread would drop out the entire patch — but the first time it happens it looks broken.

And if the sample folder is missing, Swarm Core falls back to a noise burst rather than going silent. A module that produces nothing is indistinguishable from a module that is broken, so it makes a sound whatever happens. If it sounds like noise instead of insects, the bank did not install.

Swarm Core is 18 HP and part of the Branca Series — nineteen free, MIT-licensed VCV Rack modules. Full documentation

Sample bank: InsectSet32, CC-BY 4.0.