Cardinal

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Score7.2

Rank#2 of 32

PriceFree

Free planYes

Runs onLinux, macOS, Web, Windows

Summary

Cardinal is a free, open-source modular synthesizer built as both a standalone app and a plugin, based on VCV Rack. Its bundled build includes 1,382 modules from 84 authors or brands. It runs on Linux, macOS, Windows, and the web, with AudioUnit, CLAP, LV2, VST2, and VST3 plugin formats listed. Main, Synth, and FX variants all support MIDI input and output. Main provides eight audio inputs and outputs and ten CV inputs and outputs, though it is unavailable in AU and VST2 and not yet available in CLAP. Mini offers a smaller hand-picked module set with two audio ports and five CV ports, only as LV2 and standalone. Cardinal does not load external modules or connect to the official Rack library, so users cannot add modules to an existing build. OSC remote control is available in standalone use, not as a plugin. The project describes the software as stable, while CLAP support remains in progress and VST3 hosting inside Carla or Ildaeil is experimental. It is licensed under GPLv3+.

Who it is for

Cardinal suits musicians who want a free modular synthesizer in standalone or plugin form, with MIDI support and a substantial included module set. Users who need to add external Rack modules or use OSC from a plugin should note those limits.

What is good

Free and open-source under GPLv3+.
Includes 1,382 modules from 84 authors or brands.
Standalone app and multiple plugin formats are listed.
MIDI input and output in Main, Synth, and FX.
OSC remote control works in standalone use.

What to know first

Cannot load external modules or add modules to a build.
Main is unavailable in AU and VST2.
CLAP support is still a work in progress.
VST3 hosting in Carla or Ildaeil is experimental.

Verdict

Cardinal packages a large modular synthesizer setup into a free standalone app and plugin. Its fixed module selection and variant-specific format limits matter if your setup depends on external modules or a particular plugin format.

Cardinal plans and pricing

All plans

Free Free Fully free and open-source · Cardinal builds include built-in modules; adding modules to an existing build is not possible cardinal.kx.studio · 29 Sept 2026

Compared on software synthesizers

Free plan: Yescardinal.kx.studio
Synthesis engine: modularcardinal.kx.studio
Plugin formats: AudioUnit, CLAP, LV2, VST2, VST3cardinal.kx.studio
Standalone app: Yescardinal.kx.studio
MPE support: Yescardinal.kx.studio

Facts

Product: Cardinal is a free, open-source virtual modular synthesizer based on VCV Rack and packaged as a self-contained plugin and standalone app.cardinal.kx.studio · 29 Sept 2026
Built-in modules: The home page lists 1,382 included modules from 84 authors or brands.cardinal.kx.studio · 29 Sept 2026
External modules: Cardinal does not load external modules or connect to the official Rack library/store, and adding modules to a Cardinal build is not possible.cardinal.kx.studio · 29 Sept 2026
Plugin variants: Cardinal provides Main, Synth, and FX plugin variants, with MIDI input and output support in all three.cardinal.kx.studio · 29 Sept 2026
Main variant limits: Main provides 8 audio inputs and outputs and 10 CV inputs and outputs; it is unavailable in AU and VST2, and the page says it is not yet available in CLAP.cardinal.kx.studio · 29 Sept 2026
Mini variant: Mini has a small hand-picked module selection and 2 audio ports plus 5 CV ports, and exists only as LV2 and standalone.cardinal.kx.studio · 29 Sept 2026
OSC remote control: OSC can remotely control patches and parameters in standalone Cardinal, but is not available when Cardinal is used as a plugin.cardinal.kx.studio · 29 Sept 2026
Security and privacy: The project says online access such as phone-home is not allowed for included modules and describes removing online access from the plugin and included modules.cardinal.kx.studio · 29 Sept 2026
License: Cardinal is licensed under GPLv3+.cardinal.kx.studio · 29 Sept 2026
Stability: The about page describes Cardinal as stable, while noting that CLAP support is a work in progress and VST3 plugin hosting inside Carla or Ildaeil is experimental.cardinal.kx.studio · 29 Sept 2026
Support: The maker asks users to report bugs on GitHub and lists the #cardinal IRC room on Libera.Chat for community discussion.cardinal.kx.studio · 29 Sept 2026
Intended users: The maker says Cardinal was created to provide Rack as a conventional open-source audio plugin and notes that Rack Pro may suit users seeking official support and its larger module collection.cardinal.kx.studio · 29 Sept 2026