There are multiple different sources that the user might want to start playing. Browser tab A/B/C (example: web radios), a music application or music service website in a tab that's not even opened yet (eg: spotify), the last video tab they opened (ex: youtube).
Whatever is the last thing that was paused should play IMHO. If nothing was paused, it should do nothing. Else, you open a pandora's box of possibly wrong choices that the user then has to close.
In my experience, this is a more frequent issue. At least 1 time per day, I hit play hoping to play Spotify in a browser tab or some radio tab and for some reason it opens Apple Music instead. Sometimes it could be an issue on my side, ex: the tab is dead or not even opened.
But whatever, the experience is bad: I have to wait for the Music application startup time, then click the context menu and select "Quit Apple Music". It feels like being forced to watch a product ad. Opening Apple Music is never what I want. Imagine if pressing shift opened TextEdit by default, that would be silly. Or doing CMD-v where you can't paste would automatically pop up some random app.
I feel like no machine response is a correct UX pattern in this case. The absence of sound playback would indicate to me that I need to do something else to play sound.
Whatever is the last thing that was paused should play IMHO. If nothing was paused, it should do nothing. Else, you open a pandora's box of possibly wrong choices that the user then has to close.