I have Logitech keyboard with six additional keys at the left side (G1-G6). I have 2 of them as regulator of sound, but in disco they seem not to work. But I am also sure they worked some time ago. Any suggestions?
I got a keyboard that has M1-M5 macro keys as well on the left side and discovery is using them as CTRL+1 - CTRL+5 - so if you have the game in full window it doesn't change the sound, so yeah you should try out the tutorial above.
Should your macro keys still deny to work then you should probably move the 2 volume-macros from G1-G6 to the numpad (like / and * ) those 2 keys are not used ingame and work in windowed mode for me just well...