we could go way OT with this, but it's always something .. there's one event I do now every year, I tape the event then make them a set of DVDs...it's held in a center with an incredible sound room considering that it's not really their main thing ... the acoustics of the hall are great, sound is great, and plenty of equipment to make it all work ... the engineer there is professional, good to work with, everything .. he does all the mikes, runs everything and gives me a mix on two XLR's he drops from the sound booth to me ... I set up my own mikes in the back of the room, and this year I did the same, a stereo pair. well it turns out that despite all their great equipment, that they had multiple problems with their mikes, and well it sounded not so good at all.. and it was my little mike setup in the back that saved me .. it wasn't ideal (I could have moved the mikes up in the audience) but it was enough to supplement the house sound to come up with something salvagable ... so, you never know ..

That's exactly right Mikey. The sound engineer (aka mixer guy) was explaining that to me. He provided me an audio feed that was not effected by changes to the house speakers.

He explained to me that for example, if I were in the crowd I would hear the vocals well. However if I were right next to the stage, the vocals would be low..... which is exactly what was happening. My DVC 30 "on camera" mics picked up sounds well...except for vocals.
The sound engineer is adjusting volumes to suit the room and ...parts of the music. It's important to get an audio feed that is not effected by transitory changes.