Currently, you can play n number of players at the same time. You also have to go back and pause a player if you want to play audio in another player. More info about this can be found in this thread https://forum.kde.org/viewtopic.php?f=19&t=125673&sid=ba71da6850eeb625f8345f573a5a3b2e&p=333427#p333427 Reproducible: Always Steps to Reproduce: 1. Play audio in Amarok 2. Play audio in Juk 3. Actual Results: Audio is played in both players Expected Results: Ideally pause the player which is already playing when a new player is started.
This backend for Phonon is no longer maintained or supported, and has not been for quite some time. Please use the VLC backend instead--which is the recommended and maintained replacement--and see if you can reproduce the issue there. If you can, please open a new bug report at https://bugs.kde.org/enter_bug.cgi?product=phonon-backend-vlc. Thanks a lot!