Well done; this app has been needed forever, yet shockingly missing for years. I have some homebrew solutions in Max/MSP and Ableton but they're cumbersome.

My one request / question: is there any way this could be triggered with a global shortcut? I've long dreamed of being able to record ambient audio from films while watching without leaving full screen, much like one would take a screenshot.

Alt + Command + G is the default! This can be changed from settings too :)