ed - your comment made me laugh. i often work with audio and have run a mixing board many times - outdoors and indoors.  it's always the sound "guys" fault! no matter what happens on stage.  out of tune? glare at the place you think the mixer is.. wrong note - stink eye at the mixer.  broken string? yup, as the sound "guy" , i did it.  my favorite was the lead singer who fell over his own stage monitor - once on his feet again, he started a whole stream of curses towards me. he didn't notice a cord now looped around his foot just enough to make him fall again. with his next step. he sprained his knee, missed a couple of dates and i , of course, was at fault. i had not had a part in any of his mishaps and he did not see me laughing - thank god in my little dark place with the audience. and thank god my mic was off....