I have a couple of these to add as well: VCVRack - simply one of the most mind-expanding things a synthesizer-nerd can play with. (https://vcvrack.com/ https:

I have a couple of these to add as well: VCVRack - simply one of the most mind-expanding things a synthesizer-nerd can play with. (https://vcvrack.com/ https://vcvrack.com/) ZynthianOS - another example of a simple software solution to a problem nobody realized existed, opening the door to an absolutely astonishing array of Audio processing tools (https://zynthian.org/ https://zynthian.org/)