Music: It ain't over 'til the fat man improves

Something snapped when the fairy folk of Herne's Oak stripped Falstaff down to his underpants, and it wasn't elastic. As the fat knight stood there like a giant walnut, folds of wrinkled flesh exploding outwards, the parameters of the production tore apart. What had begun as Shakespeare retold for children, in comic-strip designs and bright, nursery colours, turned grotesquely real. So real that you'd have needed sharp eyes and some familiarity with Bryn Terfel's torso to realise that all this flesh was actually a latex body-suit.

For a moment I thought: this is clever. This is rescuing the knight from caricature and re-creating him in human terms. But then the cleverness disintegrated into shambles. An unruly romp. It was a disappointment. And not least because so much was riding on this Verdi Falstaff at the Royal Opera House. The first full opera on the new stage, it just had to work, if only as a statement that the problems of the past few years were over. And on paper, at least, it looked good. Bryn Terfel was young for the title role, but a character actor with a capaciously mature voice, guaranteed to cope. Bernard Haitink was probably the one conductor with any chance of getting the orchestra back into shape after so long a time in limbo. And judging from his recent Pelleas at Glyndebourne, the director, Graham Vick, seemed promisingly back on form after a run of duds.

But the result is insecure, under-rehearsed and - worst of all, for one of the greatest of operatic comedies - not very funny. The only decent gags come with the sets (by Paul Brown), which are bold and simple but designed to show off the capabilities of Covent Garden's new stage machinery. Scenes assemble magically before your eyes as one floor slides over another, backdrops unfold like giant origami, and props descend from the fly-tower or rise from below. Falstaff's lodgings at the Garter Inn are dominated by an inflatable bed that subsequently deflates for the scene-change. And the shambolic finale around Herne's Oak involves a large piece of parachute silk which I think is meant to signify some kind of bed, in that the entire cast gets under it.

But by then, nothing seems to matter one way or another. The warm glow of benign comic genius that should have been accumulating through the past three acts barely glimmers. The characters scarcely live beyond two dimensions. And Falstaff's own moment of shocking humanity - in his underpants with all that flesh - has been and gone. Bryn Terfel sings magnificently, with an easy depth and elaborate texture. There's a forceful Ford from Roberto Frontali, a substantial Alice from Barbara Fritoli, and some agreeable cameo singing from the rest of the cast. But the performances are generally cool, slightly anonymous; when the energy level does rise, it's a false energy, exemplified by the hysterical somersaults and other acrobatic feats that make the Act II rumpus busy but not lively. There's a difference.

Like anyone with half a heart, I wanted this Falstaff to be a triumph, and it grieves me to find fault even with Bernard Haitink, who gets a rich sound from the orchestra but not much smile (it isn't light enough or fast enough: you'd think he was conducting Bruckner). But then, after everything that's befallen the Royal Opera, I suppose it's some small miracle that Falstaff has happened at all. However faltering, it's a start; and in broad terms, the omens are good. Things will sort themselves out. The only question is how long it takes.

For an example of how lively opera can be even if it isn't staged, you had to go last week to the Barbican where Sir Colin Davis was conducting Benvenuto Cellini, the first event in a long-running Berlioz series that will take in all the operas, all the major choral works, and finish with a madly grand performance of Les Troyens in December 2000. As a Berlioz- sceptic who finds much of the composer's epic writing indigestible, this doesn't thrill me. But I can't deny the stature of the music, its centrality to 19th-century Romanticism, or the innovative brilliance of its orchestration. And last Sunday night, when the LSO (the band for this entire Berlioz series) swept through Benvenuto like a dose of salts, I was completely captivated. All defences down.

Davis is the leading Berlioz conductor of modern times; and what he brings to this repertory, apart from authority, is a sense of the wit and charm that lies (sometimes well hidden) behind the bluster and bravado. With the LSO in stunning form, the LSO Chorus crisply alert, and the title role sung by an Italian tenor, Giuseppe Sabbatini, whose command of French idiom is supremely stylish, Sunday's performance was gold-star standard. Easily the big deal of the week, you would have thought. Except that three nights later, Simon Rattle turned up at the RFH.

It was for the last in the Beethoven Symphony series which the Orchestra of the Age of Enlightenment has been running with different conductors - some better than others at handling the separated (as opposed to smoothly blended) sounds the OAE produces. If you wanted proof that the man wielding the baton makes a difference, here it was in weekly instalments. Loud and clear.

But the loudest and clearest difference was Rattle, who was saved as the star turn for the grand finale - Beethoven's 9th - and surpassed even the memory of the outstanding Beethovens he did in the last years of his time at Birmingham. Then, it was a new-discovered mastery. Now, it comes with the assurance of an old hand, although there's nothing old about the vigour and exhilaration. People sometimes say that Rattle has poor technique as a conductor, and it's true that he holds the stick with an inflexibility that makes it jab and stab rather than float free. But that makes his gestures stronger. And since the purpose of technique is to communicate intention (what else could it be?), I don't see any problems. Rattle has no trouble getting what he wants. And what he got on Wednesday was an object lesson in how to make familiar music sound extraordinary - not in a perverse way but with real creative insight into why it matters. With Rattle, these days, it always matters. Which is why he's a great musician, and why his concerts hit target.

`Falstaff' continues (0171 304 4000) to 22 December