What is Annulus?
Annulus is a free instrument plugin from Jonas Eriksson, working under the name Phase Fiasco. At its core is a faithful recreation of the physical-modeling engine behind Rings, the resonator module from Mutable Instruments. It runs as AU and VST3 on macOS and Windows, and it does not cost anything.
Rings was one of the most loved things in Eurorack: a module that takes any signal and runs it through modeled strings, membranes and metal, turning a click or a noise burst into a plucked, bowed or struck tone. Annulus puts that engine in a DAW, no case and no patch cables required.
Why does Rings as a plugin matter?
When Mutable Instruments wound down, it left its hardware and code open source. That decision is still paying off years later: the community keeps porting and rebuilding Mutable's designs, and Annulus is the latest. For a house, techno or ambient producer, modeled resonance is how you get the organic, hand-played feel that a sample alone never quite has, the pluck that decays just slightly wrong, the metal that rings a touch too long.
Until now, getting that meant owning the module or hunting through workarounds. A free, DAW-native version drops the barrier to zero.
The metallic side of Annulus isn't intrinsically harsh, the way some physical-modeling plugins are.
What is under the hood?
There are six modeling algorithms, named Morphosis, Sympatheia, Bathmos, Anomalia, Donisis and Antron, each a different flavor of resonant body. The interface is deliberately stripped back, driven by four macros (Morphee, Algie, Nothros and Topos) rather than a wall of knobs, which suits sound design by ear. On top of the resonator sits an effects chain: Spiral, a stereo tape delay, Velvet, an algorithmic reverb, and twelve waveshaping distortion models for dirtying the tone.
Any catches?
It is brand new and, in the developer's own framing, not yet road-tested by a wide user base, so expect the odd bug depending on your system and DAW. It is also a recreation, not the official module, so purists chasing the exact Rings behavior should listen first. None of that costs you anything to try.
