it depends what format your recording is in.
if you have DVD audio, then the sound engineer who recorder it will place different sounds in different channels, usually voice is comming out of the center.
If you are listening to a regular CD, or video cassette, or tape, then it depends on what your receiver is set to play the sound as. In regular 2 channel stereo, then the center is not used. In DPL II, it uses the 2 channel to simulate 5.1, so a lot of the music comes out of the center channel. Personally, I can't stand DPL II for music, but it is excellent for DivX (for those who don't know what this is, DivX is to DVD as MP3 is to CD). In 5 channel stereo (available on some receivers. Denon has it), the center channel plays a collapse of the left and right channels.