After he decided to make the film,
Al Pacino invited
Frank Serpico to stay with him at a house that Pacino had rented in Montauk, New York. When Pacino asked Serpico, "Why did you do it?" Serpico replied, "Well, Al, I don't know. I guess I would have to say it would be because... if I didn't, who would I be when I listened to a piece of music?"
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