The iciest heart will melt at the moment in La Bohème when Rodolfo comments to Mimi "Your tiny hand is frozen", but somehow I doubt it is the poetry that is responsible. Opera has so many combinations of sublime music and ridiculous words that many English opera lovers prefer to partake of their beloved warbling in the decent obscurity of a foreign language: quite easily achieved, as most good operas were originally written in one. But despite many risible moments, opera can't take place without words, and like any other art the writing of librettos can be done well or badly. So what makes a good one?
The librettos for three new operas that have emerged from the Genesis Opera Project, staged at the Almeida Theatre this week, may provide some answers. The project was launched in 2001 and attracted applications from an impressive 210 composers and librettists, whittled down by a panel of judges to nine, and further whittled to three given the green light for a full production.
Among the notables on the jury is David Pountney, known worldwide as an opera director and especially in this country for his 10 years at the English National Opera, where he created over 20 productions. Pountney has also written librettos for operas by Peter Maxwell Davies and John Harle, and has translated countless others into singable modern English. If anyone knows why they succeed or fail, he should.
"Obviously a libretto has to say something interesting and inspire a composer," he begins. "But what makes it different from a play or any other dramatic work is it has to encapsulate drama but not sum it up. In other words, it leaves room for the music to say something. Conciseness is a very important attribute. One has to remember that music slows down the delivery of text at least twice or four times - so whatever it is you have to say, you have to say it in a very pithy and compact way."
Many libretti fail, according to Pountney, because they try to be too smart and pack too much in. "Don't try and write convoluted, philosophical sentences that won't be understood. It's the composer's job to set the words in such a way that they sing well, but the librettist must provide a text which is sufficiently clear. Music elaborates text, it gives all sorts of abstracts and emotional meaning which words can't give. But at the same time it obscures text, so complicated meaning becomes redundant. That's an accusation you can level at some of WH Auden's libretto writing: it's just too clever. There are clearly passages in The Rake's Progress which are too convoluted."
Richard Strauss was another composer who arguably suffered at times from his alliance with a top-flight poet, Hugo von Hofmannsthal - notably in the incomprehensible Die Frau ohne Schatten. An alternative is for the composer to provide their own libretto, but it's a course of action Pountney is loath to recommend.
"Most composers are actually lousy at it. Which is not very surprising. I can write a libretto, but I certainly can't write music - so where does this incredible arrogance come from among musical people that they think they can write words?" But Wagner managed - didn't he? "He's a very exceptional character, and as in almost every aspect of his art a disastrous example to others. He was a genius who was absolutely not to be followed under any circumstances."
Countless failures are disguised under the innocent-sounding description "Libretto by the composer", from which Pountney singles out "almost all of Tippett's operas. Most of his libretti are truly terrible." Il trovatore Pountney rates a great opera with a weak libretto, while Lorenzo da Ponte's Mozart libretti are practically beyond criticism, and Monteverdi's Coronation of Poppea "has a fantastic libretto - funny, moving, dramatically exciting. How little we've learnt in the last 500 years..."
One of the three Genesis operas is Sirius on Earth, with music by Paul Frehner to words by Angela Murphy, who seems to have thoroughly absorbed Pountney's strictures.
"The hardest thing was cutting down words to give room for the music," Murphy says, the story being a futuristic farce which includes lots of custard pie-throwing - a common expression of political dissent in Murphy's native Canada. "It was a tad painful, but always I kept in mind that less is more. Genesis has taught me that if I really want a thing to be interpreted a particular way, I've got to be quite specific, but then be willing to let it go and watch what happens."
The key concept here may be that an opera is nothing if not a collaboration - of director, singers, players, designer, composer, librettist, audience. And far from there being an antagonism between words and music, ideally composer and librettist together become something greater than the sum of their parts.
"A good dramatist can be an enormous help to a composer," Pountney concludes. "There is a Wagnerian idea of a composer having an inspired vision, with no compromise, practical, financial or artistic. But basically it's total bollocks. As we all know, if you write a novel you have an editor, who says, 'wait a minute, this is 100 pages too long'. Most artistic processes have some kind of dialogue and engagement. Contrary to the Wagnerian idea, I think this kind of discussion is entirely productive. It's very good for a composer to sit down with a dramatist who can tell him, 'no this is a stupid idea, you need a funny scene at this point'. It's a very healthy and creative process. Composers tend to be rather isolated people in any case. It's a great mistake for them to cut themselves off and create a fantasy of their own."
Genesis Opera Project ('Sirius on Earth', 'Thwaite' and 'The Eternity Man') Almeida Theatre, London N1 (020 7359 4404) Tuesday to 27 July. 'Sirius on Earth' is also at Snape Maltings Concert Hall, Snape, (01728 687110) on 1 August