Title sums it up. Only way to stop it is to kill process via terminal or to press Control + Q to quit. More discussion here: https://answers.launchpad.net/noise/+question/222273 Is this a feature or a bug?
I think it is a bug because if a program is closed then why is it still running in the process list? Also can you confirm that your player is behaving the same way as mine, as I have stumbled upon another issue: If you make a playlist and then close the Music player, it will disappear forever once you run the music player the next time. So it kind of means you cant make playlists. EDIT: you were right. its a feature. You can disable it in the options. But the playlist issue is real.