Huh?? That is really odd that there's no vocals in the center channel. I thought it was pretty much a given that 5.1 mixes used the center for vocals and some other lead stuff. Apparently not!Also I'm not sure if it's been mentioned yet, but there's a fun little easter egg hiding within the 5.1 mix. If you isolate and normalize the centre channel to 0dB there are basic mono instrumental mixes of Dogs, Pigs (Three Different Ones and Sheep just waiting to be discovered. Highly recommend!