I am using gtk-recordmydesktop to record the video output to my desktop. However, the videos have no sound. All the tutorials I found regarding this involved getting sound recorded from a microphone, while I am interested in getting the sound output recorded. How can I do this? The official FAQ says "The solution is in your mixer's settings. Keep playing with it ;)." which doesn't clarify anything.
How can I get the sound output recorded, while being able to hear it myself also?