Developer Jonas Eriksson has released Annulus, a free polyphonic resonator and effects engine for macOS and Windows.
You should note that, while Annulus is available for free download, it has not yet undergone a public beta or formal testing phase. The plugin is functional, but may contain bugs, and the developer welcomes reports and feedback from anyone who tests it.
Annulus is the latest release from Jonas Eriksson, the developer who gave us Tape Fiasco earlier this year, a free time-based multi-effects plugin.
If you haven’t tried Tape Fiasco yet, give it a go; the GUI divided opinion slightly, but it doesn’t take long to get to grips with it, and it does some very cool stuff.
This time around, Annulus offers a far less busy interface, although it still shares some design elements with Jonas Eriksson’s Fiasco plugins.
Annulus is a free resonator and effects engine, available in AU and VST3 formats for macOS and Windows.
At the heart of Annulus is a faithful recreation of the physical modelling engine that defined one of the most popular Eurorack modules ever: Rings by Mutable Instruments.
Annulus features four linked processors: Rings, Spiral, Velvet, and Distortion.
Rings is a polyphonic resonator inspired by Mutable Instruments, featuring six distinct physical modelling algorithms: Morphosis, Sympatheia, Bathmos, Anomalia, Donisis, and Antron.
Spiral is a stereo tape delay, Velvet is an algorithmic reverb, and Distortion offers twelve waveshaping models.
The six physical modelling algorithms provide a decent range of sounds from soft/harsh plucks to shimmering string-like textures.
The sympathetic string sound of the Sympathia algorithm is my favourite so far; it has a drifting, unsettled character that’s ideal for ambient soundtracks.
What I like more than any individual algorithm is that the metallic element of Annulus isn’t intrinsically harsh, like it is with some physical modelling plugins.
You can get the harsher, almost grating character when needed, and it’s great for sound design and media composition, but you also have less industrial-sounding plucks, etc., that are perfect for pop/dance music.
Annulus also features four macro controls (Morphee, Algie, Nothros, and Topos) that shape multiple elements simultaneously, enabling sweeping changes and morphing transitions.
If you give it a try, feel free to share your experience in the comments or directly with the developer; it goes a long way toward ironing out any issues.
Download: Annulus (FREE)
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Last Updated on June 9, 2026 by Tomislav Zlatic.
