What is opt-cmd-] bound to and how can I switch this off? In my newish Mojave install on an iMac I experience some odd behaviour: 


  ⌥ Option⌘ Command] plays the alert sound even if it is bound to an action in a keyboard shortcut tool like Keyboard Maestro


And it is only ⌥ Option⌘ Command], other key combinations which (to my knowledge) are not bound to anything. E.g ⌥ Option⌘ Command[ doesn't make any sound.

Also this behavior only seems to happen in one (my main) user account (other accounts - whether admin accounts or not) do not have this problem.

I cannot attribute this to any main application or menu bar app. (And I have quite a few of them!) How did I check?: One-by-one I quit all main apps and then all menu bar apps - still ⌥ Option⌘ Command] plays the alert sound.

How can I find out what causes this alert tone?  How can I find out which app/tool/daemon binds to ⌥ Option⌘ Command]?



Notes:

I care about this because I usually have on ⌥ Option⌘ Command] a particular Keyboard Maestro macro running. This still works - but additionally this unexpected alert sound plays on the shortcut. (And the sound happens even if I have Keyboard Maestro completely quit.)
I would go into system preferences > keyboard > shortcuts, and browse through all of the keyboard shortcuts and see if any have ⌘⌥]as they’re keybind. you could also open Automator, and press the record button, press ⌘⌥] and then click stop recording and see what it says that you did.