Igorski has released Phlegetron, a free distortion plugin for macOS and Windows.
I’m a big fan of Igorski’s plugins. The interfaces are always nicely designed, and the functionality tends to be focused rather than bloated with unnecessary stuff. The old Homecorrupter bitcrusher is still a personal favorite of mine, but I’m always happy to dig into a new release from this dev, and Phlegetron is another interesting addition to the lineup.
Phlegetron is a multi-distortion effect built around dual-band processing. Instead of applying distortion uniformly across the entire signal, the plugin splits the input into two separate bands and lets you distort each one independently.
The cool thing is that the split can be handled in two different ways: a traditional crossover filter or a more unusual harmonic-based split.
In crossover mode, the large central dial sets the frequency at which the signal is divided into low and high bands. This allows you to, for example, keep the low end relatively clean while pushing aggressive distortion on the highs.
In harmonic mode, the signal is separated into harmonic “bins.” One band contains the harmonic overtones related to the selected frequency, while the other contains everything else. This way, you get a more reactive and sometimes unpredictable behavior that depends heavily on the source material.
Each band has its own distortion mode selector with five options.
You can bypass distortion entirely on one band, or choose between Shape (a wave-shaping distortion), Fold (wavefolding for complex harmonics), Fuzz (hard clipping with spluttering behavior), and Crush (a digital-style distortion with quantization artifacts).
In terms of character, the distortion modes range from subtle harmonic enhancement to deliberately broken sounds.
Both bands share the same three core controls: Input Level, Drive, and Modifier. Input Level determines how hard the signal hits the distortion stage, Drive sets the overall intensity, and Modifier changes its function depending on the selected distortion type.
For example, it adjusts curve shape in Shape mode, fold threshold in Fold mode, gating behavior in Fuzz, and bit reduction depth in Crush mode.
A Link button mirrors the settings of one band onto the other for faster workflow, while still keeping the frequency or harmonic split active. The Dry/Wet control makes it easy to blend distorted and clean signals, which I find particularly useful for parallel distortion.
Phlegetron works best for getting some weird results out of harmonically rich sources like synths, but it’s also perfectly happy turning almost anything into a clipped square wave if that’s what you’re after. All parameters are fully automatable, but I think this one works best for experimentation and running into happy accidents.
Phlegetron is available as a free VST3 plugin for Windows 10 and up, and for macOS on both Intel and Apple Silicon systems. macOS users can also use it as an Audio Unit.
Download: Phlegetron (FREE)
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Last Updated on January 31, 2026 by Tomislav Zlatic.
