Benjamin Dehli Overtonium is a new free 32-channel additive Synthesizer plugin for macOS, Linux, and Windows with MPE support.
Additive synthesis has made a comeback this year. Five exciting new synths have already been released, and now another one is joining the ranks—and it’s completely free.
Benjamin Dehli has released Overtonium, a free synthesizer that offers a slightly different take on the additive synthesis workflow.
Benjamin Dehl Overtonium
Overtonium is a new free 32-partial additive Synthesizer plugin for macOS, Linux, and Windows.
There are no hidden costs; it is 100% free, and the source code is even on GitHub (LicenceAGPLv3). I can’t confirm or deny whether AI is being used and to what extent.
The UI is particularly striking. For the Overtonium, Benjamin Dehli chose a unique control concept reflected in the user interface. Unlike many additive synthesizers, the 32 partials here are structured like a channel strip.
Each partial is fully exposed within its own color-coded channel and controls—no menu-diving or multiple windows.
Each channel’s volume, for example, has its own sliders, so you can mix them precisely. This takes up a lot of UI space, which can feel intimidating when you first launch the plugin.
The synth has 32 additive partial channels; each is a sine oscillator locked to a harmonic of the played note. Each channel also comes with its own tuning settings, ADS envelope with strike and delay, and modulation.
The latter includes dedicated LFOs for the pitch and amp modulation. Plus, you have an independent noise channel with the same shaping capabilities and controls.
To refine your sounds, Overtonium features a multi-FX processor with a character (OP-AMP…) with wobble, echo (tape…), and reverb. You can use the effects together and adjust each one individually with different parameters.
It’s great that the plugin supports MPE, which you can also hear in the linked demo. Nice: pressure has its own amount on every one of the 33 channels, making it super versatile.
First Impression
A beautiful free additive Synthesizer with great sound quality. The synth really comes to life, especially when paired with an MPE controller. The demo illustrates this beautifully.
Benjamin Dehli Overtonium is available now as a free download. It runs as a standalone and VST3, AU, and LV2 plugin on macOS (native Apple Silicon + Intel), Linux, and Windows.
More information here: Benjamin Dehli
Nice!
(And it sounds like Benjamin’s last name ends in ‘I’: Benjamin Dehli)
ups, correct!