Record sound playing on the computer

Such a perfect timing, I was exactly looking for how to record sound playing on the computer. I tried gnome-sound-recorder, but it didn't show sound input drop-down, so all I can record was from the internal mic. Not anymore! I found the information at Ubuntu Weekly Recipe 技術評論社: "第137回　PulseAudioを活用する". The solution is using PulseAudio.

Steps:
1. Install pavucontrol. (aptitude or synaptics) This is GUI PulseAudio volume control frontend.
2. Run gnome-sound-recorder.
3. Push the record button. Now go to pavucontrol, and see the Playback tab. You will see "Record stream from". Choose "Monitor from analog stereo" from the drop-down menu on the right.
4. Good to go!

PulseAudio Volume ControlでのRecording tab (image from the same page)