Had to resort to a web search for my own sanity, and Audio Ducking does indeed exist:
Audio Ducking Mode
On Windows 8 and above, this option allows you to choose if NVDA should lower the volume of other applications while NVDA is speaking, or all the time while NVDA is running.
This option is only available if NVDA has been installed. It is not possible to support audio ducking for portable and temporary copies of NVDA.
Brian - Windows 10 Pro, 64-Bit, Version 2004, Build 19041
If you think that you can think about a thing, inextricably attached to something else, without thinking of the thing it is attached to, then you have a legal mind.
~ Thomas Reed Powell