Something for the weekend, sir?

Is the Royal Opera House too grand for the demon barber of Fleet Street? Michael White talks to its composer, Stephen Sondheim, about the implications of a Broadway musical breaching the sanctum of Covent Garden

"Crossover" is a dirty word these days among serious musicians, suggestive as it is of compromise, Classic FM, and the desperation of a collapsing record industry to sell more titles. So, whatever Sir Thomas Allen is doing at the Royal Opera House tonight, it isn't - he insists - crossover. And when Bryn Terfel was doing the same thing last year at the Chicago Opera, he was quick to say it wasn't crossover either.

The thing in question is the title role in Stephen Sondheim's Sweeney Todd: a role that any baritone would want to do, says Allen - ranking it effectively alongside Rigoletto, Falstaff, maybe Wozzeck in the baritonal hall of fame.

But is it opera?

It's a question people have been asking ever since the ROH announced it would be running Sweeney over Christmas. And the short answer - which certain critics have been giving with a weary, thin-end-of-the-wedge-type sigh, is No. Sweeney was written, slightly over 20 years ago, to play on Broadway. As a musical. The sort of show that Covent Garden is supposed to be too grand to do.

But Sweeney is itself so grand a piece in concept and design that it resists containment by the label "Broadway", or "West End". It beats the best Andrew Lloyd Webber into insignificance and is, by any reckoning, a work of stature by a serious composer.

Saying this, though, raises certain problems. Some would argue that Sondheim is only half a composer because, in accordance with Broadway practice, he doesn't do his own orchestration. And if you sit down and talk to him about his relationship with the world of opera, you'll find he likes to distance himself from the whole thing. He claims (probably disingenuously) not to know much repertory beyond Pelleas and Peter Grimes. And for years he has been turning down requests to write specifically for opera-house conditions - largely on the grounds of practicality.

"Whenever a house has approached me I've said OK, can I have three weeks of try-outs, night after night, with the same cast, so we can fix things before we go public ... and the answer of course is No. Because opera houses don't work like that."

So where does this leave him? Writing for Broadway where, for many reasons - not the least of them commercial - he doesn't quite belong. As he says himself: "I'm serious. But I'm serious in an art that's barely worth being called one. There's a case to be made for asking: 'Am I wasting my time?'" And if that seems like an absurd complaint to come from one of the world's most lauded living artists, it's based in fact. Sondheim has no space on his mantelpiece for any more awards, but does his music sell? Do his box-office returns compare with Evita or Phantom? They don't.

Reason: no Sondheim musical ever gives itself to the audience on a plate, Lloyd Webber-style. His storylines tend to be "difficult", non-linear, and (worse still) anti-romantic, without resolution into happy-endings or fresh-starts. His natural habitat is ambiguity, trading in characters who (as one of them explains in Company) are "sorry-grateful" and "regretful-happy".

This is not what Broadway likes. And as, one by one, the Sondheim musicals have struggled in commercial theatre, they've been thrown a lifeline by its subsidised counterpart - not least, the opera houses, which have found in Sondheim what they can't find anywhere else. New work that actually works. Which is why Pacific Overtures has its London premiere courtesy of ENO and why Sweeney has been taken on by opera companies worldwide, from Houston to Graz (where it was playing only last week).

For opera audiences schooled in stiff-backed hours of Wagner and responsive to the whispered subtleties of Mozart or Debussy, Sondheim isn't difficult at all. He's an intelligent (therefore legitimate) escape from high-brow rigour. And he can just about be placed in the honourable tradition of composers who have spent the past 70 years trying to establish a vernacular American opera that straddles the divide between high art and low: composers such as Aaron Copland, Leonard Bernstein, George Gershwin, Kurt Weill - and not forgetting Gian Carlo Menotti who, although largely forgotten these days, made a big name for himself in the 1940s with operas that not only premiered on Broadway but were designed to play Broadway-style, night after night in long runs.

Then, as now, this kind of work begged the questions: is it opera? or a musical? and what's the difference? Then, as now, it's hard to say.

The one thing you can say is that Sondheim writes with the technical skills of a composer steeped in operatic process. And he does it brilliantly. The way the long, sustained finale to Act I of Sweeney keeps everything going through successive or super-imposed solos, duets and chorus numbers bears comparison with Mozart's text-book grand finale to Act II of Figaro. Throughout the whole score, there's a mapped-out musical development that gives a sense of each song growing from, and probing the potential of, the one before. From start to finish, it's a tightly organised, coherent piece of writing. Sondheim has subtly and elegantly absorbed the methods of composers of the past. There's a massive debt in Sweeney to Debussy, but it's honourable: like a present from a pupil to his master.

At the same time, though, the debts in Sweeney are eclectic: it owes just as much to Bernard Herrmann's creepy film scores. And although it passes with flying colours one of the standard definitions of opera in that the ratio of singing to speech is high (music accounting for roughly 80 per cent) it remains a piece where the words count for more than opera normally allows. You need and want (because they're good) to hear them: which is why the voices have to be amplified, a deviant practice in the opera world. And as Thomas Allen says, "there's a weight of words against the line that you can only deal with by finding a different kind of voice to the one you'd use in Mozart or Verdi. With opera its prima la musica, poi le parole. With this it's the other way round".

And at the end of the day, does it matter? Probably not. The resistance of a score like Sweeney to categorisation may offend tidy minds, but it will defeat their best efforts. According to Sondheim himself, it's all a matter of audience expectation.

"It sounds glib, but I really think that when something plays Broadway it's a musical, and when it plays in an opera house it's opera. That's it. It's the terrain, the countryside, the expectations of the audience that make it one thing or another. And they are, in my experience, different audiences. When Sweeney first played New York City Opera and the audience gasped at the plot-twist, I thought for God's sake: this piece has been out on disc for how many years, it ran ten blocks down the road in commercial theatre, and nobody here knows the plot-twist. Different audience".

This may not be good news for Covent Garden who are no doubt hoping to extend their audience reach with Sweeney. But whoever comes to see it, Thomas Allen is emphatic that they won't be getting crossover.

"You hear that word and you think opera-singers slumming it: a 'Here I am bringing my great talent to a lesser medium' sort of thing. I don't like that. And in any case, with Sweeney I don't feel I'm crossing over into anything. I don't need a passport. The barriers are down."