Mutable Instruments' Eurorack Modules
Magical stuff. There are software versions available for free, usable in VCV Rack which is also free. I've been playing with it on and off for the last year. It blows my mind that 1) someone would just give this stuff away 2) more people aren't jumping on the bandwagon of physically based modular synths. These things can make some of the most pleasant musical sounds I've ever heard. Check out the YouTube channels "Lightbath" or "ann annie" for examples.Sadly, Émilie Gillet (the person behind Mutable Instruments) recently announced that she's stopping development of new modules, because being a known person who's visibly trans is just too much, and she's looking for the next niche to disappear in.