How to get the Mac Play Pause button to stop music?

There's something I've tried to figure out, but I can't seem to resolve it... Whenever i hit the play pause button, it automatically opens up music while i wanted to open spotify instead. i solved this with using an app like Reflex. but whenever i have a youtube video playing and i want to pause it instead it plays spotify...

Is there a way to automatically detect what media was playing last and when i press the play/pause button it play or pauses that?

[Re-Titled by Moderator]