After a fresh installation of Debian 8 jessie Xfce edition everything was working just fine, except the sound in quodlibet player. Sound was working just fine in VLC player and others, but not in quodlibet. I just couldn’t hear anything while playing songs in quodlibet player. The solution was simple though. I installed gstreamer1.0-alsa package and the sound was working again.
Open the terminal and execute the following command:
sudo apt-get install gstreamer1.0-alsa
This would solve your sound problem in quodlibet player.