That is the role of a conductor. He hears the piece as it should be heard and is active participant in "tuning" it. My understanding is that he can slow down/sp

That is the role of a conductor. He hears the piece as it should be heard and is active participant in "tuning" it. My understanding is that he can slow down/speed up various performers to get them in sync. Performers need to learn to ignore the rest and play their instrument while looking at the conductor.