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Free Filtron plug-in from Polyverse

Equipped with versatile saturation options

Polyverse Filtron free self-oscillating resonant filter plug-in with saturation

Polyverse’s latest release, Filtron, is a state-variable filter plug-in that also offers some built-in saturation processing and interesting modulation capabilities. Best of all, it is being offered as a free download.

The plug-in centres around a 12dB/octave filter that can transition between low-, band- and high-pass modes, is capable of self-oscillation, and boasts a resonance control which Polyverse says will go up to 11! All of the key filter parameters can be adjusted using three large Type, Cutoff and Res controls in the centre of the GUI, whilst In and Out sliders provide a pair of level controls to maintain gain through the plug-in.

A Drive section then offers a built-in saturation algorithm for introducing distortion alongside the filter stage. The company say that the plug-in’s saturation features a soft-sounding curve, and that the filter will react differently and produce varying results that are dependant on the input level. The section is also equipped with a post-filter overdrive effect which has two different modes: Hot and Cold, the first of which is described as a screaming overdrive, whilst the second offers a warmer, more fuzz-like tone.

The plug-in’s parameters can also be modulated using CV generators — such as the company’s own Gatekeeper plug-in) — with each channel in a stereo pair able to be targeted as an individual destination. Polyverse say that Filtron has been optimised for audio-rate modulation.

Interestingly, the company’s CEO has described the plug-in as “the second filter in the Polyverse Filter Trilogy” after the recently released Supermodal [reviewed here in SOS May 2023 print / web / app / replica / PDF editions], so it looks as if there may be a third instalment already in the works.


Filtron is supported on PCs running Windows 7 and above, and Macs running macOS 10.9 or higher. It is available in VST2, VST3, AU and AAX plug-in formats.


Filtron is available now as a free download from the Polyverse website.

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