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]?
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.)