Only a few of the other comments mention the dialogue of this movie, which I think is superb! The verbal sparring between Marietta and Captain Warrington is a delightful contrast to their soul-mated singing and elevates this film above other musicals of the era. One always suspends disbelief when viewing any film, of any era (come on, you don't think modern films are really "real", do you?), and it may be difficult for some to enter into the mindset of a '30s moviegoer, but with not too much effort even those who say they don't like this type of film, or these actors, or whatever, can find something to enjoy in this film. (Just call it a fantasy, without special effects.) Some of the opening scenes are almost embarrassingly silly, but quite soon the movie hits its stride and the music, humor, and sweep of the story carry you along. As an untrained actor in his first real role (singing cameos don't count), Nelson Eddy does quite well, thank you; I am inclined to think that the oft-repeated comment about his "wooden" acting style may owe more to L. B. Mayer's jealousy (remember what he did to John Gilbert?) than to a true assessment of his skill (which, admittedly, did improve over time). Mayer wanted MacDonald for himself and the obvious attraction between Eddy and MacDonald, coupled with her stinging rebuffs of Mayer's advances, made him no good friend of "the baritone". (Bear in mind, too, that Eddy was not interested in being an actor; he used film to advance his concert career.) I think this is a grand film, almost my favorite of the duos' work. "Maytime" has an edge because I had the good fortune to see it on the big screen when it was re-released in 1962, and I've only seen the others on television. The music in "New Moon" is glorious, and Nelson and Jeanette seem to be having such fun together in "Sweethearts".... All I can say is, if you have the opportunity to see MacDonald/Eddy films on the big screen at a film festival or revival theatre, don't pass it by!
