How to make sure the Play/Pause button works on your Mac

At one point in macOS history, if you had a Play/Pause button on your keyboard, it kept “focus” on whatever the last music app you used was. Then Apple broadened that to include anything with a music player. You could be in iTunes and use the keyboard to pause playback, then switch to YouTube in a browser, press play, and the keyboard would help you play and pause there, too.Or at least most of the time. In my experience and that of many people who post about it, the last music play