All the software I could find that does this is broken on macOS Sierra and will probably break again in the future, so I need a solution to set the system volume in the same increments as the volume keys without needing a 3rd party app running.
If my understanding is correct, keyboards with generic media controls work without software, if I could rebind my PrintScr and Scroll Lock keys as volume up/down that would be ideal. (I'm using a fullsize Majestouch 2 with ANSI layout.)
If that isn't possible, any Service or other Workaround is welcome. I can actually work without the bezel as long as the increments are the same.
Karabiner was one of the apps I used before, it doesn't work either and isn't likely to be fixed soon: macOS (10.12) compatibility #660