Yes, it was Rhythmbox (the window title for Rhythmbox is just Music Player).
$ apt-cache policy rhythmbox rhythmbox: Installed: 0.11.5-0ubuntu8 Candidate: 0.11.5-0ubuntu8 Version table: *** 0.11.5-0ubuntu8 0 500 http://us.archive.ubuntu.com hardy-updates/main Packages 100 /var/lib/dpkg/status 0.11.5-0ubuntu6 0 500 http://us.archive.ubuntu.com hardy/main Packages -- Music player starts in all user sessions https://bugs.launchpad.net/bugs/242982 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs