Airy by HARMONICO dsp: Free Stereo Widener VST
A smarter way to add stereo width
Airy is a free stereo widener released by HARMONICO dsp in August 2026. Instead of applying the same widening treatment to the whole signal, its main PERCEPTUAL engine measures how wide each frequency region already is and adds only the extra Side information needed to approach your target.
The result is a widening tool with a more deliberate approach to mono compatibility. Airy processes the Side channel while leaving the mono sum structurally intact, making it particularly interesting for producers who want more space without casually sacrificing the center of a mix.
What is Airy?
Airy takes its name from the Airy diffraction pattern, the optical pattern created when a point source of light passes through a circular aperture. HARMONICO dsp turns that idea into a visual and technical metaphor for stereo coherence.
The plugin’s PERCEPTUAL engine analyses stereo width across multiple frequency regions. You draw the target width on the stereo field map, and Airy fills in the missing width rather than automatically pushing every part of the signal farther apart. The PERCEPTUAL engine operates at zero latency.
Mono-safe by design
Airy’s key idea is simple: the widening processing lives in the Side channel. The Mid information is not rewritten by the widening stage, so collapsing the result to mono preserves the original mono sum. You should still perform normal mono checks, but the architecture gives Airy a strong foundation for mixes that need reliable center information.
More than a one-knob widener
Although the interface is immediate, Airy contains considerably more control than a basic width knob.
- PERCEPTUAL engine: measures the existing inter-channel width and adds what is missing toward the chosen target.
- Stereo field map: lets you shape the desired width across the frequency range.
- GENERATE: creates stereo information from mono material in compatible hosts.
- DIFFUSION: changes the character of the generated width from focused to more diffuse.
- MONO BELOW: keeps low frequencies centered below a chosen cutoff.
- CORR POS: provides a correlation safeguard useful when preparing material for vinyl or broadcast.
- RIDE: makes the amount of width respond to the source or an external sidechain.
- Two assignable LFOs: add synchronized movement for creative widening and sound design.
- SPECTRAL engine: offers an alternative, more phase-textured widening character.
- A/B, randomize and parameter locks: make experimentation faster without losing a useful starting point.
Where Airy can be useful
The plugin is a good candidate for sources that need space around a strong center rather than indiscriminate width across the entire mix.
Open up sustained layers without automatically exaggerating parts that are already wide.
Generate width from mono backing vocals or create more room around a centered lead.
Increase apparent size while using the correlation tools to keep the result under control.
Use small width moves and MONO BELOW for subtle stereo polish rather than an obvious effect.
Official Airy demonstration
The short official interface demonstration below gives a quick look at Airy’s visual approach and stereo-width workflow.
Compatibility
Price: Free
License: Free, no activation required
Formats: VST3, AU and AAX
macOS: macOS 10.15 or newer, Intel and Apple Silicon
Windows: Windows 10/11, 64-bit
AAX: Pro Tools 2023 or newer
Three quick starting points
- Stereo synth or piano: raise the width target gradually and let the PERCEPTUAL engine leave frequency areas that are already wide largely alone.
- Mono pad or backing vocal: use GENERATE to build stereo information, then shape its character with DIFFUSION.
- Bus processing: keep the move subtle, center the lowest frequencies with MONO BELOW and compare regularly in mono.
Why Airy stands out among free wideners
Airy is not simply another free utility with a Width control. Frequency-aware targeting, mono-to-stereo generation, low-frequency management, modulation and two different processing engines give it enough depth for both practical mixing and more experimental sound design.
Most importantly, the plugin is genuinely free. There is no activation system or account requirement. HARMONICO dsp asks for an email address on the official page and sends the download link directly.
Official HARMONICO dsp download page
