Found a new toy this week and I am honestly a little blown away. CA-72 is a free synth from a small outfit called Idle Foundry, and it is a love letter to the early 70s Minimoog Model D. Not a rough approximation either. They transcribed the actual service documents of a 1972-73 unit into SPICE netlists and modeled the voice circuit in ngspice. That is a level of nerdery I respect.
Like the original it runs monophonic, and the basses and leads out of this thing have that thick, slightly unhinged Minimoog growl that sits perfectly under a wall of distortion. But then you hit POLY mode and it gets weird in the best way: each note gets its own full instrument, up to 10 voices, each with its own keyboard circuit, contours and glide. The ENTROPY knob is my favorite thing here. It makes every voice its own slightly off specimen, tuning and filter and envelope times all drifting a little differently, like the chips came from different production batches. Dial it up on a pad and it starts feeling alive. SPREAD throws those voices across the stereo field, which the mono original could never do.
There is also a FEEDBACK knob that recreates the old trick of cabling the headphone output back into the external input. Push it and the input stage overdrives until the OVERLOAD light kicks on. Into a distorted industrial bass line that is pure menace. And since the host side chain feeds the external input, you can run anything through that saturation.
It ships with 24 factory presets covering basses, leads, pads and percussion, including a drum kit and a riser built on the panel alone. The preset browser has search, tags and favorites. Runs VST3 and CLAP on Mac, Windows and Linux, plus Audio Unit on Mac.
Price: free, open source under GPLv3. Get it here: https://github.com/idlefoundry/ca-72