South Pacific: Chuck out the cheese

'South Pacific' - that's a schmaltz-filled musical, right? Wrong, says Robert Butler, who reveals the darker themes of the story highlighted in a new production opening at the National Theatre this week

If you say to someone that you're doing South Pacific, they'll sing song after song to you," says John Shrapnel, one of the principals in the National Theatre's new production of the musical. "It's astonishing how many people know pretty much every song in it. And yet, if you say, 'Do you remember the theme of the show?', they don't."

The theme of the show is a major selling point in director Trevor Nunn's revival. When South Pacific opened on Broadway in 1949 it became the first musical to win the Pulitzer prize for drama. Nowadays many of us could hum along to "Some Enchanted Evening", "I'm Gonna Wash That Man Right Out of My Hair", "Bloody Mary", "Happy Talk", "Cockeyed Optimist", "Honey Bun" or "Bali Ha'i". But the reason that it won the Pulitzer Prize – the drama itself – was it something to do with a French bloke on a beach falling in love with a blonde?

Not exactly. South Pacific is the only major American musical to be set in World War Two and it opened only four years after the war ended. As South Pacific's musical supervisor, David White says, "Imagine staging a musical in four years' time called Afghanistan." One aim in this revival will be to prise South Pacific away from its associations with "cheese" and "schmaltz". In America during the Forties, the South Pacific denoted a place where tens of thousands of men in their late-teens and early 20s lost their lives. The war is only the background to a plot which deals with the way two attractive young Americans – Joe Cable, a lieutenant in the marines, and a naval nurse, Nellie Forbush – discover the depth of their own prejudices. The marine falls in love with a Tonkinese girl. The nurse falls in love with a Frenchman called Emile de Becque who has two children and whose first wife (now dead) was Polynesian. Both the marine and the nurse go through crises and break off from the people they are in love with.

When Nunn approached the Rodgers and Hammerstein estate about doing Oklahoma! at the National in 1998, James Hammerstein, one of the lyricist's sons, urged Nunn to take a look at South Pacific. Nunn was shown the script that was used on the first day of the first rehearsal in 1949. He studied the rewrites, cuts and changes that were made when South Pacific had its first try-out performances in Boston and New Haven. He was lent Oscar Hammerstein's own copy of James A Michener's Tales of the South Pacific, on which the musical was based. Nunn could see how Hammerstein's ideas developed.

Michener's novel is a series of 19 interlinked stories. "It's structured like a Robert Altman movie, like Nashville," says Nunn, "You get disparate groups of people and for a long time they don't connect up." Rodgers and Hammerstein homed in on two stories and cherry-picked details from the others, to bring their own preoccupations into focus. "You could readily sit down and choose three or four other stories," says Nunn, "and never have to deal with anything about colour prejudice. There are all sorts of ways you can go. What's wonderful about having Hammerstein's copy, with all the pencil marks, is you can see from his markings: 'I'm interested in that bit of content. I'm interested in those things because they're tough and contemporary and ask questions'."

When South Pacific had its try-outs in Boston and New Haven, the production ran past 11pm, so the director Josh Logan called in his friend, the playwright Emlyn Williams, who suggested a number of cuts. (Rodgers and Hammerstein were also the producers, and it was prohibitively expensive to pay overtime to the backstage crew.) Nunn has restored two songs that were cut and reinstated a number of provocative passages of dialogue. These sections strengthen the main theme and heighten the parallels. Put simply: if one young person has a prejudice, it might be a character flaw; if two young people share a prejudice, it tells us something about the society in which they grew up.

The orchestration has undergone the same thorough make-over as the text. Imagine "Some Enchanted Evening" in the wrong hands: it could be as corny as Kansas in August. "They didn't have microphones in those days," David White explains, "so in order to get the tune up onto the stage, so that the singers could hear it, they had to double it and treble it, and it meant for a very thick, gloopy orchestration at certain moments. It's led us to explore ways to freshen up our ears, particularly the way we get into a number."

The new intro to "Some Enchanted Evening" uses a section buried within the earlier orchestration. "Originally it was an old-fashioned dance tune with a whole orchestra," explains the orchestrator William David Brohn, "I think it was perfectly marvellous in 1949, but it doesn't read well now. It's not truthful now. We've stripped the first 16 bars down to only harp, cello counterline and bass pizzicato. We sneak the audience into it."

In South Pacific we meet Americans, French, Polynesians and Tonkinese, but no Japanese. The plot deals with the way white America gets along with those on its own side. There's a key moment when de Becque refuses to join the fight "against the Japs". He feels his love for Nellie outweighs what's at stake in the war. He stumps Captain Brackett by asking, "I know what you're against. What are you for?" Earlier, Emile tells Nellie that he believes in freedom for everyone. Nellie asks, "Like in the Declaration of Independence?" Emile replies, "C'est ca. All men are created equal, isn't it?"

"In 1943, that wasn't what American society was living out," says Nunn, "I'm not saying it is an anti-American moment or there is a disloyal intention about the show. But there is a questioning." It wasn't until 1955, for instance, in Montgomery, Alabama, that Mrs Rosa Parks refused to give up her seat to a white person on a bus. Her arrest resulted in Martin Luther King leading the boycott against the buses and that led to the Supreme Court ruling that bus segregation violated the Constitution.

There is a direct line between the social idealism that fuelled Jerome Kern and Hammerstein's breakthrough musical Show Boat in 1927 – with its magnificent "Ol' Man River" – to South Pacific 22 years later. Nellie is from Little Rock, Arkansas. The show ends with her on the terrace of de Becque's house, embracing de Becque's children. A southern girl is becoming the mother of an interracial family. "And where is the show being performed?" asks Nunn, "It's being performed in America in 1949. That's the resonance."

It resonated loudly enough with politicians in Georgia, when South Pacific toured to Atlanta. One State Representative said, "In the South we have pure bloodlines and we intend to keep it that way." Legislation was introduced outlawing entertainment that had "an underlying philosophy inspired by Moscow." Hammerstein's reply was to express surprise that "anything kind and humane must necessarily originate in Moscow."

'South Pacific', RNT, London SE1 (0207 452 3000), previews from tomorrow, opens 12 Dec. Sponsored by Barclays. 'Staging South Pacific', by Robert Butler, available at RNT bookshops from 18 Dec