I don't hear Dennis at all in What You Do To Me, but if I put the dvd into my other dvd player I use as a "CD player" and turn the volume up a bit, I can hear Dennis rather enthusiastically congratulating Carl after the song ends. It's quite touching, if a bit sad because his voice is so hoarse you can't quite make out what he says. By the way, you can actually hear(and see) Dennis saying "Are you ready?" before the show starts.
The way that show started, with each of the Beach Boys being driven onto the field, and over to the stage, made for a very long introduction. I think Dennis was getting impatient at waiting for the other guys to get there. IIRC, Dennis and Mike were up there first, Brian and Carl were last.