I did what you recommended and it goes into Theater View when I play an audio or video file, abandoning Standard View.
I'm suggesting a feature where that view would be displayed within the MC window in standard view, so I can still see all my other rows, menus, trees, etc. without using full Theater View.
(My Theater View setting sends it to my TV monitor. But my Standard View setting displays the MC window on my computer monitor. They are in 2 different rooms. Therefore, going into FULL Theater View doesn't work for me for that reason as well. But mainly, it's because I want to retain the wonderful browsing and searching capabilities the MC Standard View window provides, while enjoying the amazing "Playing Now" feature I see in Theater View.)