I'd just sit back and watch. Set up a few cameras to reflect back on/find out his secrets later... but just bask in the glory of the closest thing to God that any of us will ever meet.
this would be sick, although then again, i would hate a real big artist coming to me, as i'd know i wouldnt be able to deliver the sound as good as many other audio engineers could.
i would feel like i'm waisting there time, knowing they could be some were better