Context: The FM-1 is an inexpensive synth ($80ish on amazon/aliexpress) which was reverse engineered [0]. The company that makes it now endorses the open firmware movement around it [1] [2].

You can see a review for the synth here [3].

Wow, also see "Firmware Hub"! [4]

[0] https://github.com/aroum/fm1-custom-fw

[1] https://github.com/m-vave/fm1_open

[2] https://forum.m-vave.com/topic/4

[3] https://www.youtube.com/watch?v=q3e2zH_-5I8

[4] https://thefirmwarehub.com/