When I was in grade school between 1951 and 1957, I remember a field trip to an afternoon children's concert with the Cincinnati Symphony conducted by Max Rudolf. When I was in college, I sang in the chorus of Händel's Messiah that he conducted. He was a wonderful man. Then came Bernstein and his TV programs, and I guess my first knowledge of a show conductor was Franz Allers, from the recordings of My Fair Lady and Camelot and a fantastic Merry Widow. By the time I was in college, Allers was conducting the Lincoln Center productions, including their recordings of Merry Widow, Show Boat, etc., produced by Richard Rodgers. After that, he recorded some classic German operettas in German for EMI.