Field of Dreams (1989)

Factual error: Joe Jackson batted left-handed in real life, not right-handed as Ray Liotta portrayed. He also threw right-handed and not left-handed like it shows when Kevin Costner is hitting him fly balls to left field.

Terence Mann: Ray, people will come Ray. They'll come to Iowa for reasons they can't even fathom. They'll turn up your driveway not knowing for sure why they're doing it. They'll arrive at your door as innocent as children, longing for the past. Of course, we won't mind if you look around, you'll say. It's only $20 per person. They'll pass over the money without even thinking about it: for it is money they have and peace they lack. And they'll walk out to the bleachers; sit in shirtsleeves on a perfect afternoon. They'll find they have reserved seats somewhere along one of the baselines, where they sat when they were children and cheered their heroes. And they'll watch the game and it'll be as if they dipped themselves in magic waters. The memories will be so thick they'll have to brush them away from their faces. People will come Ray. The one constant through all the years, Ray, has been baseball. America has rolled by like an army of steamrollers. It has been erased like a blackboard, rebuilt and erased again. But baseball has marked the time. This field, this game: it's a part of our past, Ray. It reminds of us of all that once was good and it could be again. Oh... People will come Ray. People will most definitely come.

Trivia: The town in Iowa that the movie was filmed in was Dyersville. The actual house and farm used in the movie are about 2 miles outside of town and are open to the public.

Question: At the end of the movie, the Voice is credited as Himself. Who was really responsible for doing the voice that sent Ray on his journey?