Hammerstein, Bernstein, Blitzstein, Jule Styne - the great names of American musical theatre are Jewish.
How does a nation express itself? In Habsburg Austria, the means were operetta and waltz time. But, if empire and operetta were two hearts beating as one, who was plucking the strings? Emmerich Klmn was Jewish, so was Fritz Grunbaum; even the Strausses came from a Jewish family. After the Anschluss, the Nazis decided to Aryanize show business. White Horse Inn was unacceptable because of its Jewish authors, so Fred Raimund was signed to write Season in Salzburg: it had all the yodelling and other hokum of White Horse Inn, but no Jews. It was never anything other than a poor substitute.

Adolf Hitler took a personal interest in these matters. As a young man, he had returned again and again to sit in the gallery during the long run of The Merry Widow, and his love for the work never diminished, despite the fact that both librettists were Jewish, as was the composer's wife. Franz Lehr was Hitler's favourite musician and thus untouchable, but his collaborators weren't so lucky. His librettist Fritz Lohner-Beda died in a concentration camp in 1942, the same year his Land of Smiles was produced with Lehr conducting. To the end, he expected his partner to intercede and save him. But Lehr either couldn't help, or wouldn't help. Recalling the awards the old man had accepted from the Nazis, Alan Jay Lerner said: "To this day, when I am transported by the music of Franz Lehr, my glass of champagne is rimmed with aloes," - a fine operetta image. Whatever the truth, after Lehr's death there was no more champagne. In removing Jews from the theatre, the Nazis ended up throwing the bathwater out with the babies. Result: end of operetta; death of Austria's musical voice. Those crowds of happy Austrians cheering Hitler into Vienna were hailing the death of their own culture.

At the turn of the century, Vienna and New York were not dissimilar: two teeming cities, both high-density human experiments in multiculturalism. We know about the pogroms that drove the Jews from Eastern Europe to America - if only because we've seen Fiddler on the Roof. But less easy to explain is how so many of those Jewish immigrants jostling together on New York's Lower East Side made the journey uptown to Broadway. One man's progress became the American dream incarnate: as George M Cohan introduced him at the Friars Club, "a Jew boy that has named himself after an English actor and a German city" - Irving Berlin.

"Irving's seven years older than me," says Irving Caesar, lyricist of "Swanee" and "Tea For Two", "but we both grew up on the Lower East Side, like a lot of songwriters - Kalmar and Ruby, the Gershwins. Our parents arrived from Europe at Ellis Island and they just settled in the ghetto - those were the days before immigrants started moving north or out to Brooklyn. I've never known why so many songwriters came from the East Side, but I will say this. The Jewish immigrants always liked to rhyme. You'd call out to one, `Izzy', and he'd say, `I'm not busy'. Most of us learned from the little Jewish patter songs of those days."

On Broadway, the Jews prospered. By the 1860s, "Hebrew citizens" were assiduous theatregoers, as they are to this day; and, as they also remain, Jews were becoming prominent backstage, too: Ford's Theatre, to name one example, was run by the Jewish H B Phillips, until the assassination of Lincoln forced its closure. Later came Belasco and the Shuberts and the Hammersteins. Broadway's Jews gave the American people their voice. It was Jerome Kern who, cautiously, accidentally even, Americanised the theatre song. He and Oscar Hammerstein were at one time planning a musicalisation of Donn Byrne's Messer Marco Polo. "Here is a story laid in China about an Italian and told by an Irishman," said Hammerstein. "What kind of music are you going to write?"

Kern replied: "It'll be good Jewish music."

By then, good Jewish music was good American music. The pioneer Alleymen had been Jewish: Charles K Harris, Edward Marks, Monroe Rosenfeld. And before that there was Henry Russell, an English Jew who lived in America and wrote, among others, "Woodman, Spare That Tree" and "A Life On The Ocean Wave". But it was Kern, Berlin, Gershwin, Rodgers, Arlen and all who followed who established the brassy/modest, raucous/tender vernacular of Broadway song. Cole Porter, the token Wasp, took longer to hit the big time. Moneyed and Protestant, he felt he would never be able to write genuinely popular songs, until one day he told Rodgers that he'd stumbled on the formula.

"What is it?" asked Rodgers.

"Simplicity itself," said Porter. "I'll write Jewish tunes."

And so, in a way, he did. Except for Arthur Schwartz ("Dancing In The Dark") and some of Sigmund Romberg ("Softly As In A Morning Sunrise"), Porter was the only Broadway composer to write in the minor key - brooding chromatic sinuous melodies that warmed and deepened his nonchalant lyrics. That's the magic ingredient many other exhibitionist rhymesters miss, and which kept him in business from 1929 to the late Fifties. As Rodgers noted, "It is surely one of the ironies of the musical theatre that, despite the abundance of Jewish composers, the one who has written the most enduring `Jewish' music should be an Episcopalian millionaire who was born on a farm in Peru, Indiana."

At which point, perhaps, we should consider what we mean by "Jewish" music. The definitive work in this field is by A Z Idelsohn who, in a survey of Jewish folksong from Eastern Europe (which is where most New York songwriters, or their parents, came from) observes that 88 per cent of this traditional music uses "the minor scale or at least has minor character" - hence, Cole Porter's Jewish tunes. We can look elsewhere for "Jewishness" in America's music, too: in the "blue notes" of Gershwin's showtunes and, most famously, his Rhapsody, an almost organic soundtrack of the city, as Woody Allen recognised in his film Manhattan. A "blue note" is the third, fifth or seventh degree of the scale, with its pitch tweaked slightly to give it a bluesy, jazzy tinge. The minor third can be a "blue note" but, in its broader sense, it's also characteristic of Jewish folk-song. It's an interval you find all over the score of Porgy and Bess, in "My Man's Gone Now", "It Ain't Necessarily So" and several other songs: yes, the score sounds bluesy and southern and Catfish Row on a lazy summer day, but, if you set it in Eastern Europe, you'd realise also how Jewish it sounds. "S Wonderful" is a minor third tune, and apparently lifted from "Noah's Teive", a song in Abraham Goldfaden's Second Avenue Yiddisher operetta Akeidas Izchok (1908): instead of "'S Wonderful, 's marvellous", they sang "Kum zu mir in Teive arein" (Come to me in the ark).

Here, I can't resist quoting Idelsohn's stupendous (10-volume) Thesaurus of Hebrew-Oriental Melodies: "The Jewish folk has never attempted to add harmonic combinations to its music. The song remains for single voice. In all likelihood because of his Oriental origin, the Jew prefers melody. To him, music means melody, means a succession rather than a combination of tones."

It's a provocative theory: as far as American song is concerned, you can find plenty of harmonic invention in Kern and (perhaps more surprisingly) Berlin. But, at heart, Idelsohn is right: Christianity has produced great choral music; the Jews prefer the solo cantor. Kern believed that the true test of a song was that, if you tapped it out on the piano with one finger, it still sounded good: "Long Ago And Far Away" passes, as does "They Didn't Believe Me" and "The Way You Look Tonight". I'm not sure how many of the classical gang you could say that of. But it does get to the crux of the difference between Broadway and the standard song, on the one hand, and rock'n'classics on the other.

Was it coincidence that the arrival of the Jews in Tin Pan Alley and on Broadway also saw the birth of the "standard" song? Or did some deep, instinctive understanding of their inheritance lead them to create works which pared composition to the essence? Idelsohn's description of Jewish folk music is virtually a definition of the "standard": a song for single voice, built on melody - a melody so muscular that it shrugs off the pop fashions of the day and endures for decades.

A standard is not an art song: nobody does Schubert as a bossa nova. But the principles underlying traditional Jewish music seem to have been inherited by their Broadway descendants. We think we can hear these elements in the songs of the city, in the plaintive moans and blue notes. But the supposedly urban Jews gave the mountains and prairies their soundtrack, too. Who would deny the authenticity of Hammerstein's poetry for Carousel, whether lyrical and capering ("That Was A Real Nice Clambake") or dark and brooding:

You can't hear a sound - not the turn of a leaf

Nor the fall of a wave hittin' the sand

The tide's creepin' up on the beach like a thief

Afraid to get caught stealin' the land...

Whether American audiences know or care about the Jewish contribution to their culture is a moot point. But it's fitting that the show that marked the end of the Golden Age should have been specifically Jewish, almost a piece of collective autobiography, a farewell to the world those Lower East Siders left behind: Fiddler on the Roof. Even after its success on Broadway, the creators were advised that it was "too Jewish" for London, for Europe, for anywhere except New York and its Jewish theatre parties. They were wrong every time. During the Tokyo run, a fan of the show came up to the librettist Joseph Stein and marvelled that the show could even have worked in America because "it is so Japanese". Yes, it is. It's about Jews in the far-away dim and distant Russian Empire, but it's also about tradition and change - and that's Japanese, and Dutch, and Australian. On Broadway, the Jews universalised their culture.

But musicals are such an artless art that the better you do your job, the less credit you get. Thus, the best Nazi song is by Jewish songwriters. As with "Ol' Man River", when Cabaret called for an ostensibly innocent pastoral hymn to German nationalism, John Kander and Fred Ebb turned in such a plausible doppelganger that it was immediately denounced as a grossly offensive Nazi anthem. "The accusations against `Tomorrow Belongs To Me' made me very angry," says Fred Ebb. "`I knew that song as a child,' one man had the audacity to tell me. A rabbinical person wrote to me saying he had absolute proof it was a Nazi song." It wasn't: it was written in the mid-Sixties for a Broadway musical. But today it's the only Nazi song we all know: on election night 1987, when Spitting Image decided to draw some crass parallels between Mrs Thatcher and another strong leader, they opted to show the Tories singing not the Horst Wessel song but "Tomorrow Belongs To Me" - secure in the knowledge that we'd all get the joke.

In Cabaret, we first hear the song sung by the waiters at the Kit Kat Klub as they clear the tables at the end of the day: it's beguilingly innocent. Only at the end do we see the swastikas, only later do we hear the martial tempo rise inexorably from within that bucolic ballad. "What's really awful," says John Kander, "is when it's taken for what it doesn't mean. I can remember a Jewish boys' camp calling us excitedly for permission to use the song in their camp show. I thought to myself, I don't think they quite get this."

As Mel Brooks' Springtime for Hitler recognised, musical theatre and Nazism have certain qualities in common: Hitler's Germany is a bad musical - crudely manipulative, robotically choreographed, reducing individual characters to one faceless chorus performing in unison. Still, you'd have thought the subject beyond the vocabulary of the form - until Cabaret gave it a go. "If You Could See Her Through My Eyes," sings Joel Grey as he dances with a tutu-ed gorilla. But it's the final line, hissed by the leering Emcee to the audience, that tells you what the number's really about:

"If You Could See Her Through My Eyes ...

She wouldn't look Jewish at all."

During Cabaret's try-out in Boston, a rabbi wrote to the authors saying that the ghosts of six million Jews were begging them not to use that last line. More pressingly, real live theatre parties were considering cancelling their bookings. "It was the first show where we had a crack at success - not just John and me, but Hal Prince, too - and we were all more frightened than we might be today," says Fred Ebb. "But they were threatening to close us down before we opened, taking ads out accusing us of anti-Semitism. So, because of the pressure, I changed the punchline to what I thought was a very weak line. I'd thought our intention was very clear, but even in the movie, when Bob Fosse shot the song, if you notice, `She wouldn't look Jewish at all' is said with absolutely no accompaniment; Joel just whispers the line. And that's so, if Bobby had any trouble from people, he could substitute the line without getting the musicians back in. He was still afraid."

By the 1987 Broadway revival, Prince, Kander and Ebb could afford the courage of their convictions. It's a moment of pure musical theatre: the emcee sings the final line; we laugh, and then catch ourselves in the huge mirrors hanging over the stage; the laugh dies instantly, as we realise what we're laughing at, and the song shrivels to a shamed, stinging silence and some awkward applause. It happens so quickly. But, in only a moment, with seductive ease, we have journeyed from fun to mockery to bigotry. "I'm very proud of that reaction," says Ebb, "and it's exactly what the mirror concept means in Cabaret - that we're all capable of this." Music, lyrics, plot point, choreography, design and involuntary audience participation have fused to create an effective theatrical shorthand. Through song and staging, a point has been made which would require pages of straight-play dialogue: musical theatre

From `Broadway Babies Say Goodnight', by Mark Steyn, published by Faber and Faber on 1 December, price pounds 20. Copies may be bought by credit card (p&p free) by telephoning 01279 417134 and mentioning this offer

Stage-struck: Adolf Hitler loved The Merry Widow (above, filmed in 1925 by von Stroheim) so much he returned again and again to see it on stage; his enthusiasm meant that Franz Lehr (far left) was untouchable. Below left: Irving Berlin, one man who made the journey from the Lower East Side to the bright lights of Broadway

Tuned in (left to right): Cole Porter, who decided success lay in writing `Jewish tunes'; Oscar Hammerstein, who helped give America its soundtrack; Jule Styne, best known for Gypsy and Funny Girl

Smash hits: Kander and Ebb's Chicago (above), with Ute Lemper, currently running in the West End; Fiddler on the Roof (left), the musical that explains how Jews from eastern Europe came to be living and working on New York's Lower East Side