Fractone

A polyrhythmic undertone synthesiser, built as a VST3 and Audio Unit instrument. Version 1.1.0.

Two oscillators, each carrying two subharmonic dividers from f/1 to f/16. Four rhythm generators dividing one clock by 1 to 16. Two four-step sequencers turning those whole-number ratios into patterns that interlock and drift apart. Everything lands in a resonant four-pole ladder filter and a VCA, with a 32-point patchbay for moving the signals around inside.

The Fractone panel: oscillators with subharmonic dividers, four rhythm generators, two sequencers, filter and patchbay

What it does

Undertones: Rather than stacking harmonics above a note, each oscillator divides down from it. Whole-number division means everything you get is in tune with the root by construction, and the further down you go the stranger the intervals get.
Polyrhythm: Four rhythm generators each divide the same clock by a whole number. Set them to 3, 4, 5 and 7 and the pattern takes 420 beats to repeat. That is the instrument.
Sequencers: Two four-step sequencers, driven by the rhythm generators rather than by a single clock, so the two lines move against each other.
Filter and VCA: A resonant four-pole ladder filter and a VCA, shaped by the envelopes.
Patchbay: Thirty-two points with working cables, for re-routing the signals inside the instrument.
Clock: Follows Live by default, with an optional free-running TEMPO. MIDI notes behave the way they do on the hardware this follows: they transpose and they gate the envelopes.
Presets: Patches save and recall, cables included.

The panel is read top-left to bottom-right, the same way the signal flows: tempo drives the rhythm generators, which advance the sequencers, which play the oscillators, which feed the mixer, filter and VCA. Hover any control for a description; drag knobs up and down, and double-click one to reset it.

Video

Walkthrough video — not up yet.

Documentation

Getting started (PDF) — your first polyrhythm in Live, a tour of the panel, first patches and troubleshooting.

Every control is documented in the project README.

Download

Builds for macOS, Windows and Linux are on the releases page. The macOS archive has a VST3, an Audio Unit and a standalone app, universal for Apple silicon and Intel. Installation notes are on the front page.

Source

github.com/taddeimania/fractone — C++ and JUCE, AGPLv3.