During the Landry years, the Cowboys lineman would head to the line of scrimmage and set down, then stand to hide the players behind them, who were quickly changing positions, before resetting (called a "chorus line"). But with the multiple set offense, the opposing team didn't know what was going on in the middle of the play, and who was in what position. I know this was used to prevent the other team from using tendencies (or keys) to guess the play call. I have a number of questions about the practice and why it is no longer used (or did anyone ever use it outside of the Cowboys)? I think multiple sets are still used today. I know Bledsoe calls a run and a pass and can check off to one or the other at the line of scrimmage. Does this run vs pass "audible" prevent a multiple set offense? Does a multiple set offense have a place in today's game? Can defensive players be confused about the play if they miss a change in the backfield?