A free, open-source, self-contained modular synth plugin.
DISTRHO is an open-source project for cross-platform audio plugins. And provides its own plugins and Linux ports, everything being open-source. LV2 and VST versions are always available, sometimes with LADSPA and DSSI as well.
Cardinal is a free and open-source virtual modular synthesizer plugin, available as CLAP, LV2, VST2, and VST3 audio plugin for FreeBSD, Linux, macOS and Windows. AU and Jack or Native audio standalone are available for some systems. Cardinal is based on the popular VCV Rack but with a focus on being a fully self-contained plugin version. More specifically, this is a DPF-based plugin wrapper around VCV Rack.
The plugin was created first and foremost as a way to have Rack as a proper open-source audio plugin. A proper audio plugin should be self-contained as much as possible, as to not interfere with the DAW/Host, and loading external modules clearly goes against this idea.
Cardinal contains Rack, some 3rd-party modules, and a few internal utilities all in a single binary. It does not load external modules, and does not connect to the official Rack library/store. All ‘core’ modules from Rack have been replaced by Cardinal equivalents, and simplified to better work for an audio plugin.