Sound Radix, a company better known for pitch and time-correction tools like Auto-Align and Surfer EQ, has stepped into synthesizer territory with Radical1, a modular additive synthesizer currently in preview release for macOS (Windows support is planned to follow). What makes Radical1 worth a closer look for the MPE community isn't just its unusual sound-generation engine — it's that the instrument was built from the ground up to respond to per-note expressive control.
A different approach to additive synthesis
Traditional additive synths ask you to manage banks of individual harmonics by hand, which quickly becomes unwieldy. Radical1 sidesteps that with a patent-pending engine capable of generating tens of thousands of oscillators while keeping CPU load in check. Instead of programming harmonics one at a time, players shape entire spectral shells through what the company calls Morphing Fluid Oscillators and Spectral Sample Resynthesis — techniques that let a single gesture reshape hundreds of partials at once.
That matters for MPE users because spectral movement is exactly the kind of parameter that benefits from continuous, per-note control. A slide gesture on an Osmose or a Roli keyboard can sweep the harmonic content of a single note in real time, while a neighboring note held on the same MPE surface stays untouched — something that's simply not possible on a standard MIDI channel.
Built-in MPE readiness
According to Sound Radix's product page and early coverage from Sound On Sound and Synth Anatomy, Radical1 offers polyphonic per-voice processing with sample-accurate envelopes, meaning each note gets its own independent modulation lane rather than sharing a single global envelope. Combined with MPE-ready expressive control, this lets per-note pitch bend, pressure, and timbre modulation feed directly into the additive engine — ideal for continuum-style controllers, MPE guitar controllers, and grid instruments alike.
The plugin ships in VST3, Audio Unit, and AAX formats, so it slots into most modern DAWs without extra configuration. During the preview period, Sound Radix is offering the plugin at an introductory price of $129 (down from a planned $199), with a rent-to-own option for those who'd rather spread the cost.
Why this release stands out
Additive synthesis has a reputation for being powerful but fiddly, and MPE controllers have historically been paired most often with subtractive or wavetable instruments — think Pigments or Osmose's onboard engine. Radical1's arrival signals that expressive, gesture-driven control is starting to reach synthesis methods that were previously considered too complex for real-time manipulation.
For sound designers who already own an MPE surface, that opens up a genuinely new sonic palette: sweeping a finger across a Seaboard or LinnStrument to morph a spectral shell in real time is a very different experience from automating harmonics with a mouse. Because the engine is still in preview, expect ongoing updates — Sound Radix has said it will keep refining Radical1 based on user feedback before the Windows build ships.
Getting started
Musicians curious about pairing Radical1 with their MPE hardware can grab the current preview build directly from Sound Radix's site or through retailers like KVR Audio. As with any preview-stage plugin, it's worth checking current known issues before committing a session to it, but the underlying idea — additive synthesis that responds to the same per-note gestures MPE players already rely on — is a promising direction for expressive sound design.
If you're new to pairing additive or spectral instruments with an MPE controller, start simple: map slide or pressure to spectral tilt rather than every parameter at once, and let the per-note independence do the work that a single mod wheel never could.