Full Bucket Music is offering a free beta version of their ModulAir modular polyphonic software synthesizer for Microsoft Windows (VST) and Apple macOS (VST/AU). It does, however come with a warning - a spokesperson had this to say...
"ModulAir is a work in progress, unfinished, buggy, as of now with only a few quirky presets. Expect horrible things to happen. It is a clumsy unhandy complicated piece of software. I cannot even guarantee that the next version of ModulAir is backwards compatible to any version you may download in the future or might already have downloaded. You have been warned! Anyway, ModulAir is currently in Beta stage. I am not sure if it ever reaches the General Availability stage since I am constantly adding modules and stuff to it."
Pricing and Availability: