Mix of midi generators, instruments & effects. Free & open source.

https://danja.github.io/downspout/

They are very much in-progress, feedback appreciated.

The Linux releases work for me, the Windows versions have limited testing, the MacOS versions still untested.

The "not exactly" process : https://github.com/danja/downspout/blob/main/docs/process.md

(I am a coder by trade, not my first rodeo etc)