Enjoy, finally we get this option back that was missing in 10.1/10.2.
Use the volume keys to control playback, and the convenience key to play/pause. Headset controls similar, most models use double click to skip songs and more.
Remember to enable these options in Settings → Main Volume.
I don't know what OS you are talking about, but for me sideloaded/.apk installed music players did not register as music players (i.e. no Play Icon in the status bar). And that meant the Skip/Back/Pause function of the hardware keys did not work for them.
But maybe I overstated it, of course I never checked all of them.
At least it is nice to see more of them having this option. Now if only it would extend to all video playing apps as well, fingers crossed!
BlackBerry Passport signed @ Nintendo Social BBM Channel @ C001221B2
Mine has play icon on the status bar. And it's running on 10.2.1 -or at least it was- The app name is MX player and i can use the hardware key on OS 10.2.1
Maybe it's just the app.... i don't really understand either.