There it is in bold, gold capital letters: THE MASTERPIECE REBORN AS A MUSICAL. The classy poster for Trevor Nunn's long-planned new production of Porgy and Bess says it all. With its logo looming beautifully out of a glossy black surround, and a lustrously-toned sepia close-up of a couple with their lips forming a prelude to a kiss, it confidently promises everything its composer, George Gershwin, could have wanted. It conjures up sensuality, seriousness, passion, its black cast (as stipulated in his will) and, of course, music. What it resolutely avoids mentioning is the potentially audience-killing fact that Porgy and Bess is actually that supremely unfashionable thing: an opera.
Or, at least, it was. Ten days after its New York premiere on 10 October 1935 - where it had been hailed by the theatre critics, but largely derided by classical music critics sniffily unimpressed by the temerity of a mere Broadway composer making his full operatic debut -Gershwin mounted a vigorous defence in The New York Times: "Because Porgy and Bess deals with Negro life in America it brings to the operatic form elements that have never before appeared in opera and I have adapted my method to utilize the drama, the humor, the superstition, the religious fervor, the dancing and the irrepressible high spirits of the race. If, in doing this, I have created a new form which combines opera with theatre."
That new form, which he labelled "folk opera" begged any number of vexing questions. Was this really opera? Surely, with all those stand-out songs like "I Got Plenty O' Nuttin' " and "Bess, You Is My Woman", not to mention "Summertime", wasn't this a musical? That conundrum has dogged not just this piece but almost every other vaguely ambitious musical composition to surface in either the commercial theatre or in the opera house.
And wherever you look, crossover appears to be the name of the game. Rufus Wainwright is flirting with a commission for New York's Metropolitan Opera; Stephen Schwartz, composer/lyricist of the mega-hit Wicked is writing his first opera. At the same time, an entire generation of American composers (most of whom, bizarrely, have three names ie Jason Robert Brown, Michael John LaChiusa, Ricky Ian Gordon) are infused with a missionary zeal of high seriousness in an attempt to stretch the boundaries of what constitutes a musical. And the moment that any of these projects sees the light of day, the same debate will be reignited.
The problem with the urge to pigeonhole is that the activity has little to do with the music and everything to do with arrant snobbery. Keepers of the operatic flame will have you believe that upstart musicals are salad cream compared with operatic mayonnaise: less sophisticated, far sweeter and dangerously mass-produced. Jeremy Sams, who has translated and directed operas and is currently directing The Sound of Music, believes this panders to popular prejudice and is entirely spurious. "If you think that opera is highbrow and musicals are lowbrow it shows you know little or nothing about either."
That said, the shallow end of the musicals pool is horribly extensive. Truly great musicals are extraordinarily rare. Indeed, the A-list is not much longer than Cabaret, Carousel, A Chorus Line, Guys and Dolls, Gypsy, The King and I, My Fair Lady, Sweeney Todd and West Side Story. Why? Because, unlike operas which are composer-driven, musicals are supremely collaborative. They rely upon the dramatic meshing of a consistently strong script (aka "the book"), music and lyrics, all of which tend to be written by different people, and that's before the choreographer and director put their oars in. Technically speaking, Elton John and Lee Hall wrote Billy Elliot but without Peter Darling's dance and Stephen Daldry's direction the show wouldn't exist.
Mind you, weigh up the opera catalogue for similar synthesis and nine-tenths of that will also come out wanting. Dazzlingly prolific Donizetti was dead in a madhouse at the age of 50 from syphilis. Opera-haters might suggest the cause of death was really exhaustion: he spent his entire adult life writing 75 operas, an average of two a year, awash with terrific singing opportunities and terrifyingly little satisfying theatre. And yet, in their magisterial later works, Mozart and Verdi armed themselves with seriously good librettists to create commandingly dramatic pieces of theatre.
Conductor/arranger Gareth Valentine, the man entrusted by the Gershwin estate with re-orchestrating and refashioning Porgy and Bess into a musical has a clear sense of the divisions: "Opera is about the music, musicals are about the word. When I go to the opera I want to hear beauty. I hear impressive, dramatic voices in musical theatre but I've yet to year a truly beautiful voice."
But it's not just about sound. He's alert to the fact that opera has dead moments. "Musicals tend to be lean. When you work on them it's a question of 'Hey, do we need those four bars there?' It's never a question of allowing music for its own sake, it has to be there for a reason. You can't have characters or audiences waiting for music to finish."
That explains much of the cutting that has taken place for the slimline musical version. It's not a job Valentine took on lightly. He turned it down twice. Now he regards it as a labour of love. That said, his approach sounds like radical surgery. All the long-winded, stylised recitative is out, replaced by spoken dialogue. Ditto the huge orchestral sections written largely to cover scene changes. Gone, too, is a large chunk of the orchestra which in 1935 ran to 56 players. Not that Valentine's band is tiny. At 20, it's the second largest in London after Phantom of the Opera which boasts 22.
Nunn famously directed the full operatic version at Glyndebourne in 1988 and again at the Royal Opera House where it came in at around four hours. His trimmed-down version is coming in at 2 hours and 20 minutes plus one interval.
According to Valentine, this is achieved not solely by cutting. "Tempi are faster than in an opera where things can get lugubrious." As a result, the performers don't have to sustain sound for sustaining's sake. The aim is to keep everything moving, which is very much an imperative in theatre which, whether sung or spoken, happens live in front of a paying audience.
Unlike the private business of reading a novel, theatre is an activity dependent upon being in public. Thus commercial theatre, utterly reliant upon box-office, forces composers of musicals to please their paying public. Opera composers are, to a large extent, relieved of that necessity. Generally speaking, contemporary opera commissions are cushioned by the luxury of (largely) public subsidy in the UK or private sponsorship in the USA or a mix of both. That frees them to wrestle merely with the art-form and their inspiration. In other words, their creation is led by the art. On the other side of the divide, it's even more complicated. You don't have to be an embittered cynic to come to the conclusion that whereas operas are written by composers, in many instances musicals are now written by producers.
Serious Broadway and West End talents would hotly deny that assertion. Yet it is an inescapable fact that spiralling costs make putting on a musical an extraordinarily risky business - and it really is a business. The oft-quoted industry maxim still stands: you can make a killing as a producer, but you cannot make a living - one idea might take off but no matter how hard you try to clone success, every show is different. That, you would imagine, would deter anyone but the terminally foolhardy; but the fact that Cats has made more money than Titanic has lured many a novice producer to take the plunge. Hey, if a 1,232-page redemptive historical bestseller of decades of love, war and justice (Les Misérables) can be a worldwide mega-hit for Cameron Mackintosh, why not a 960-page redemptive historical bestseller of decades of love, war and justice (The Far Pavilions)? Because, to borrow the song title, it ain't what you do, it's the way that you do it.
As the benighted team behind The Far Pavilions (and countless other musical producers) have discovered, the longed-for break-even point - ie the minimum weekly take required to cover everything from cast and crew wages to the costs of rehearsal, scenery, costumes, lighting, sound, props, rights, royalties, publicity and marketing - can be a crippling sum in excess of £200,000. (And just to make the equation even harder to balance, 17.5 per cent of the box-office revenue immediately by-passes the producers and goes straight to the treasury in the form of VAT).
To maximise audience numbers to reach break-even, recoup costs and make anything approaching a profit, there's intense pressure on every element being engineered to "deliver", to "work" for an audience shelling out a top price of £60. The responsibility for that rests with the producer. Boublil and Schonberg wrote Les Misérables and Miss Saigon but not for nothing is it routinely described as a Cameron Mackintosh show. And as anyone who has worked on one of his hits, and especially his flops, will tell you, Mackintosh is absolutely not someone who sits blithely by letting the talent do their own thing: he's the man who put "hands-on" in the dictionary.
Conversely, as Mackintosh's highly profitable global operation proves, the potential longevity of a musical presents economies of scale that opera houses can only dream of. Once a musical has recouped its capitalisation, running costs drop in several areas. Most opera productions, however, receive just a handful of performances. From the mid-1980s onwards, English National Opera has got its money's worth out of countless revivals of Jonathan Miller's famous Mafia-style Rigoletto, but that's because it can repeatedly restage a now familiar production of a tune-filled repertoire staple. Fiercely dramatic though David Alden's similar vintage production of Tchaikovsky's Mazeppa was (known forever after as The Chainsaw Mazeppa), the opera itself is a connoisseur piece, a rarity with a limited audience that no house would consider reviving on a regular basis.
Only rarely can musical theatre support a similar degree of bold experimentation. "Safety first" tends to be the producer's mantra. High ticket prices mean audiences are, understandably, becoming seriously risk-averse. They want security, as close as they can get to a guarantee that they will get their money's worth and have a good time. Which is why producers tend to offer up an audience-friendly known title (Dirty Dancing, The Sound of Music), a pre-existing score (Mamma Mia, We Will Rock You where you go in humming the tunes) or something more dangerously different shored up by a star name (David Soul in the recent Mack and Mabel).
The combination of all that has led, with rare exceptions such as Shockheaded Peter or Jerry Springer - the Opera (so expensive to run that it made little or no profit), to the form growing ever more conservative. Which leads us to the case of Stephen Sondheim.
Continually revivifying the dramatic potential and even the language of musical theatre has won Sondheim accolades and acolytes but his work has never had the blockbuster success of his contemporary Andrew Lloyd Webber. Why? Because, he is incontrovertibly the leading radical in what is now an essentially reactionary form. At its simplest, audiences want - or, rather, think they want - more of the same; Sondheim has dedicated himself to the promise of "and now for something completely different". His A Funny Thing Happened On the Way To The Forum is laugh-aloud farce with songs attached; Pacific Overtures is an uniquely orchestrated and spellbinding meditation upon imperialism and cultural identity; Sweeney Todd is a grand-scale, grand-guignol musical thriller. No opera house is likely to stage A Funny Thing... but English National Opera mounted Pacific Overtures as far back as 1987 and Sweeney Todd has been done in numerous houses, not least in the UK at the Royal Opera House in 2003. Next June Covent Garden will also stage his Into The Woods. All of which puts Sondheim in a unique position to deliver a verdict. So what's the difference between operas and musicals? The audience.
"When Menotti's operas The Medium and The Telephone were staged in theatres, they were seen as musicals. When Sweeney Todd was done at New York City Opera, it was opera. The difference is about expectation, what audiences bring to the piece."
Opera, he believes, is largely about the demands on the voices. "It's more akin to a rock concert than theatre. It's about people going to see a particular performer. Opera audiences go to whoever is singing Tosca. They're there for the singer not the song."
Unsurprisingly, it's not to his taste. "Opera is full of lingering moments. For me, if people spend five minutes saying 'good night' it's too long. I want to know what happens next. Even an aria as beautiful as "Vissi d'arte" - it comes at a highly dramatic point in the plot and I want the drama to continue."
That would appear to be the imperative behind Valentine and Nunn's approach. Valentine goes so far as to argue that some of Gershwin's original writing was forbiddingly self-conscious: "This was his first full-scale attempt at writing for opera singers and some of the choices of keys are gratuitous, written very high to show off the voices. But it's to the work's detriment. Sung so high, you cannot hear the words. We've taken them down sometimes over half an octave. The sound is more honest, it's earthier."
Sondheim has neither heard nor seen a bar of Valentine and Nunn's new version but he believes that a leaner version would have appealed to Gershwin. Well he would, wouldn't he? After all, they're both men of the theatre. Which may just be the answer. The opera vs musicals classification isn't just about audience expectation: it's about the creators' intention. Gershwin believed he had written a folk opera but opera and musicals live on through the imagination of their present day re-creators. It may sound like sitting on the fence, but if Valentine and Nunn believe they're working on a musical, they probably are.
* 'Porgy and Bess' opens on Thursday at the Savoy Theatre, London (0870 164 8787). 'Into The Woods' will open at the Linbury Theatre at the Royal Opera House, Covent Garden , London (020 7304 4000) in June next year