Full Bucket Music, have a rich history in developing free VST and AU plugins, they have a really wide range of different emulations and original designs. Just check out their site. ModulAir 1.0 is their first modular synthesizer and its polyphonic!, which is notoriously hard (or expensive) to do in the modular world (although it is getting easier)
ModulAir is written in native C++ code for high performance and low CPU consumption. It was previously only available as a Public Beta. However as is noted by the developer;
ModulAir is a work in progress and as of now with only a bunch of quirky presets and a lousy documentation. I am constantly adding modules and stuff to it. :-)
Features:
Donations for ModulAir are encouraged, so if you're using it and enjoying it, why not jump over to Full Bucket Music and chuck them a couple of quid ;-)
Revisions that turned synths into brand new machines
The Avila Brothers talk about their journey to the recent Super Bowl Halftime Show