Click here to watch the original Broadway cast sing a medley

Time to shine a light on the invisible men. Considering how many hits they accumulated in their prime - they are up there with John, Paul, George, Ringo and Elvis - the Four Seasons are as anonymous as any gang of backroom musicians. Frankie Valli needs no introduction, of course, though most people would be hard pushed to tell you anything about him, except that he sings in a falsetto and played Rusty Millio in The Sopranos. But can you name any other members of the long-running group? Probably not.

Which is one reason why the Broadway success of Jersey Boys came as such a surprise. There is nothing new about the concept of the jukebox musical - New York and the West End are awash with them, and any canny producer knows that the quickest route to a fortune is to bring together a loud band, a few dance routines and a stash of vintage pop singles. But who would have bet on a show about the Four Seasons taking the box office by storm? Surely the band were too anonymous to acquire a significant theatrical following?

Then again, you might have said the same about the collected works of Abba. And, as it turned out, Jersey Boys amounted to more than an immaculately restored jukebox. There was a story here: the tale of four young Italian-American guys who knew all about the rituals of the street and the temptations of petty larceny. It helped that the musical opened at a moment, in 2005, when The Sopranos was just about the hottest programme on American television. Above all, the musical had a nuanced book co-written by Marshall Brickman, Woody Allen’s screenwriting collaborator on Annie Hall and Manhattan.

With a four-part structure reflecting the disparate viewpoints of the group’s four members, the script aspired to more than a cut-and-paste job. If the PR-spun comparisons with the multiple viewpoints of Rashomon were overblown, Jersey Boys still served up a pungent slice of social history. And, while some of the revisionist claims being made for the Seasons are exaggerated - for all the craftsmanship, the music seldom reaches the heights of the Fab Four or the Jersey Boys’ rivals, the Beach Boys - it’s impossible not to be impressed by the sheer quantity of their golden oldies.

While the early chart-topper Sherry drew its inspiration from doo-wop, Valli and co delivered assured dancefloor pop (Walk Like a Man), polished blue-eyed soul (Working My Way Back to You) and supper-club balladry (Silence Is Golden and many others). Valli’s pure but tough falsetto also paved the way for the all-conquering Bee Gees disco formula of the 1970s. That was a good decade for the Seasons, too: after seeing their sales fade at the end of the 1960s, the band were back in contention with two of their best numbers, Who Loves You? and the nostalgic coming-of-age saga December 1963 (Oh, What a Night).

In the 45 years since Sherry raced up the charts, the group’s personnel has undergone multiple changes. Indeed, Valli has enjoyed a successful solo career. But it is his friendship with the songwriter and keyboardist Bob Gaudio, who quit touring and performing many moons ago, that defines the Four Seasons sound. In a deal founded on a handshake, the pair have built an imposing commercial edifice. Shrewd businessmen, they made a point of maintaining control of the publishing rights to their many recordings. (One of the dramatic climaxes of Jersey Boys comes when they discover that one of the group’s founder members, the guitarist and all-round rough diamond Tommy DeVito, has run up debts with the mob. Valli and Gaudio subsequently borrowed money to buy him out of the band and settle his debts.)

Sitting in a West End hotel suite, jet-lagged after arriving from a promotional event in Chicago, the two men look every inch the assured music veterans. Valli, small and dapper, enjoys ambling down memory lane. Sometimes he is all alone down there: his poor hearing, the result of a middle-ear ailment, means he has a habit of going off at tangents whenever he misunderstands a question. Gaudio, tall and rangy, is the more sardonic. While Valli, inevitably enough, is the centre of attention whenever fans descend on them at performances of Jersey Boys, his friend is happy to slip out of theatres all but unrecognised. Not that he is spurning this belated moment in the limelight. “I’m still trying to figure out whether we really are alive or whether this is some sort of bizarre dream,” he quips.

It’s ironic, in a way, that the two men are the toast of Broadway, as they belong to a generation that came close to killing off the traditional musical. With the rise of Elvis and the Brill Building, the language and mores of Rodgers and Hammerstein and their contemporaries began to seem increasingly quaint. You could argue, in fact, that theatreland’s composers and lyricists have spent the best part of half a century trying to come to terms with the challenge. The preponderance of glistening jukeboxes in our theatres is a sign, many would say, that the battle has already been lost.

As far as musicals go, Valli and Gaudio are men of conventional tastes. “I say, thank God for Lloyd Webber,” Gaudio says, “because he singlehandledy saved the musical.” Phantom and Evita are the shows they admire most. In terms of spectacle, that is. When I make the none too controversial observation that West Side Story dwarfs anything the good lord has given us, Gaudio shifts position slightly. “As music, West Side Story is the best of them all,” he concedes. “But I’m talking about theatre. I think you’ll find a lot of West Side’s reputation rests on the movie, not the original stage production.”

And how does Jersey Boys fit into the canon? Valli thinks the show gives a voice to “the working guy”, much as the hit Big Man in Town did more than 40 years ago. “The nice thing about this show is it was not written around the music,” he says. “It was written out of reality. Music just happens to be part of it. Personally, I never looked at it as a jukebox musical.”

During its New York run, Jersey Boys has built a following among the so-called “bridge and tunnel” audience of unfashionable suburbanites. “Here was a show with an instant lock on its market,” wrote Time’s critic, Richard Corliss. The sad truth, as he observed, is that if theatre cannot weave magic of its own (how many shows have conquered popular culture since the days of Hair?), it will have to settle for recycled gold dust. Which is precisely why the jukeboxes are playing at full volume. Corliss added: “Once I was a youth who spent his happiest summers on the Jersey shore, singing and listening to songs very like these. And now, as a Manhattan snob, I have a message for dear old Broadway: you need shows pretty much like this one.”

It’s no surprise that Gaudio and Valli concur with those sentiments.

Gaudio believes that part of the strength of the show’s music lies in its artful blend of genres. “There are so many twists and turns in this music. That gives the story an edge. It’s not that it’s Sondheim, but it has what theatre needs now - and has needed for a while - and that’s energy.I hate to sound like we’re music mavens, but I think this show is setting the bar for musicals. And I don’t just mean catalogue shows. I think writers are going to look at creating music that has some twists and turns, that doesn’t stay in just one genre. I think the audience out there is thirsting for an eclectic evening of energy.”

Jersey Boys is currently in previews at the Prince Edward Theatre, W1

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