There are very few classic musicals or plays that were filmed/taped in the theatre (as opposed to excerpts on variety shows). In America, due to union issues, it was almost impossible. In the UK, though, it occasionally happened. In 1952, with the approval of writer-producers Rodgers and Hammerstein, someone went into London's Drury Lane theatre and recorded a performance of South Pacific (given specially for the cameras) on 16mm film, with one microphone hanging over the stage and sometimes visible. It was apparently made for the private use of Rodgers and Hammerstein, and the R&H Organization has the footage, but some of it has found its way onto YouTube: three excerpts, providing us with an opportunity to see what co-writer/director Joshua Logan's production looked like. Logan at this time was one of the very best stage directors in the world -- he'd done Annie Get Your Gun for Rodgers and Hammerstein (as producers), and had just written and directed Mister Roberts before he did South Pacific. It's hard to believe such a smart, alert stage director is the same guy who made the bloated, boring, screwed-up film version of South Pacific, but Logan's awfulness as a movie director doesn't need to be elaborated on here.
Mary Martin repeated her New York role in London (Martin loved touring; she did the road company of Annie Get Your Gun because Ethel Merman refused to tour), and Emile was played by Wilbur Evans, a deep-voiced Broadway baritone who had been the romantic lead in Cole Porter's Mexican Hayride in 1944.
Here is the first excerpt, the first 10 minutes of the show (stopping, unfortunately, just before "Some Enchanted Evening"). The main technical device of the show is apparent immediately: transparent curtains. Jo Mielziner, Rodgers' favorite set and lighting designer, would let the next scene slowly fade into view behind the curtains, and then the curtains would part to reveal what we had already seen. In terms of scene-to-scene transitions, this meant that the next scene would start to appear before the previous scene was finished: one scene would fade out of view as the next scene faded into view. Or sometimes one scene would fade out, someone would do something in front of the darkness, and the next scene would then fade in behind them (sometimes allowing the character to step into the next scene).
I hadn't realized that Mary Martin played Nellie so ditzy in the opening scene. Also: no microphones. What a thrill to hear the voices in an actual theatre acoustic.
The transparent-curtain technique was an attempt to mimic the cinema technique of the dissolve (Rodgers, Hammerstein and Mielziner had used something similar in some parts of Allegro). The biggest problem with musicals has always been the scene transitions: because musicals tend to use more sets than non-musicals, there is always the question of what to do while the next scene is being set up. The most durable solution to the problem was perfected by writer/director George Abbott (another frequent Rodgers collaborator), who would do short scenes in front of the curtain while another scene was being prepared. Many classic musicals, whether or not they're directed by Abbott, use this technique; that's why, in Kiss Me Kate, "Brush Up Your Shakespeare" is sung in front of a decorated curtain while behind that curtain, the set for the finale is being moved into place.
Eventually, musicals moved more toward the idea of having one big set for the whole show, accomplishing scene changes by moving the characters from one part of the set to another. (Like almost everything in musical theatre since the War, this was based on something Rodgers and Hammerstein had already tried, in this case with Allegro, which eliminated representational sets and therefore set changes.) This sped up the scene transitions and also gave the whole production a sense of unity and theme. In South Pacific, though, the sets themselves were pretty normal and representational, and each scene had to have its own more-or-less unique set. Here is Martin performing "I'm Gonna Wash That Man Right Out of My Hair."
And here, on the same set, is a big scene between Nellie and Emile and her next big number, "Wonderful Guy."
This number also demonstrates another thing that was unusual about South Pacific, the naturalistic dancing. R&H's last three shows had all been extremely dance-heavy shows choreographed by Agnes DeMille, and before that, Rodgers had done many musicals with George Balanchine. For South Pacific, there were no extended dance numbers, and what little dancing there was in the show was mostly handled by Logan himself. In this number, Nellie dances the way somebody actually might dance around if she could hear the music playing (note that the orchestration suggests the possibility that it might be playing on a radio somewhere). The show is therefore an important milestone in showing how to bring a sense of movement and flow to numbers without stopping the show for self-contained dance numbers or bringing on dance doubles for non-dancers the way Oklahoma! did.
Note the transition at the end: the scene fades out behind the girls, and the next scene is about to fade back in when the clip ends.