NEW YORK (AP) — It seems all but unthinkable today: A major TV network hires a famous composer to write an original opera and broadcasts it live in prime time on Christmas Eve. But it was a different world in the early days of television back in 1951 when Gian Carlo Menotti’s “Amahl and the Night Visitors” premiered on NBC to an estimated audience of 5 million children and adults. With its tuneful score and uplifting story of a Christmas miracle, the opera — broadcast from a studio at NBC headquarters in Rockefeller Center — proved an immediate hit with viewers and critics.