In case anyone's wondering what that cool synthesizer that he's using is, it's a Eurorack[1] modular synthesizer[2].

If you are at all interested in this, I'd strongly encourage you to check out Muffwiggler[3], a huge forum for modular synthesizer enthusiasts.

Also useful is the Modular Grid[4], a gigantic database of thousands of amazing modules (and which also lets you design your own modular setup using these modules).

VCV Rack[4] is also great for playing around with software versions of some of these modules, which can be pretty expensive (the guy in the video has likely invested thousands and thousands of dollars in to his Eurorack setup, while VCV Rack is free). On the other hand, you can also build your own Eurorack modules (see the DIY forum on Muffwiggler for that), which can be a lot cheaper.

Something else I was thinking about was that if the main problem the guy in the video was trying to solve was that the knobs and switches on his modules were too difficult to manipulate with his prosthesis, then he could have tried the HackMe Vectr[5][6], which would have let him simply wave his whole hand around above the module to send out three voltages from his hand movements in three dimensional space. Mind control is, of course, way cooler, and doesn't require movement at all.

Finally, I was also thinking about how his modular interface might have been designed with opto-isolators, to minimize the risk of voltage inadvertently being sent back from the modular in to his arm, should he plug his cable in to an output rather than an input. Someone with more of an electronics background than me can probably comment on whether this would be a good idea.

[1] - https://en.wikipedia.org/wiki/Eurorack

[2] - https://en.wikipedia.org/wiki/Modular_synthesizer

[3] - https://muffwiggler.com/forum/

[4] - https://vcvrack.com/

[5] - https://www.youtube.com/watch?v=HSoVBz-1eQ0

[6] - http://hackmeopen.com/Vectr/