One of the best lessons I've learned from barbershop (and it came from Mr. Holy Moly himself, Jim Casey) is that we each have to find our own voice. There's no sense trying to sound like anybody else but yourself! We can learn lots about good vocal production from our heros, but there is only ever going to be one Barbra or Mel, and there is only ever going to be one person on the planet with your voice! And that is one of the reasons that I love to sing.
"Practice does not make perfect - Practice makes permenant". (Mac Huff)
When you're singing barbershop, the exact pitch will be close enough. (unknown)
"Breathe, you fool!"
Regardless of how entertaining it might be to the performers NOTHING should happen in front of an audience that hasn't been planned and rehearsed.