Voltage Modular is a free VST/AU virtual “modular case” for macOS and Windows compatible with most DAWs. It also runs as a Stand-Alone soft-synth.
Developers can freely design and publish modules with the equally free Voltage Modular Designer, and there’s a bunch of both free and paid modules available from a range of DYI as well as more established vendors.
This is a collection of 45 Voltage Modular modules by PSP Audio – a very affordable way to get started with an array of must-have modules.