OK, I upgraded to 11, set it to Apple TV. The music played thru the whole house system and was still distorted. I had quit Airfoil. Not sure where to go next.
I have a set of speakers that sound static-y when iTunes via Airplay or Airfoil send them sound at max volume. If I simply turn down the sound to those speakers in Airfoil or iTunes, the static goes away and I can crank the speakers up loud without any static.