Il Barbiere di Siviglia, Glyndebourne

"We're off to Glyndebourne, to see a ra-ther bor-ing op-ra by Rosseeeni," quoth songwriting wags Kit and the Widow. So here it was at the Sussex house after a 34-year absence, the most famous of all his operas which includes the overture’s oboe tune to which those words were set, and it wasn't possible that The Barber of Seville, pure champagne, could ever be boring. Or was it?

Cast and conductor have been near-perfectly chosen. Enrique Mazzola is a crisp and elegant master of Italian opera buffa at Glyndebourne, his beat clear and high to make sure no-one on stage slips a beat or gets out of synch in those difficult patter ensembles. The London Philharmonic's phrases and the many solos in the Overture - no newcomer for Barbiere, since Rossini had used it twice before - breathe vocal delight, and inner details like the lower string patterns in the big crescendo register beautifully in the wonderful acoustics. Continuo work from fortepianist Andrew Smith and cellist Pei-Jee Ng is deft and wry. The very first soloist on stage, young Huw Montague Rendall from the Glyndebourne Chorus in the comprimario role of Fiorello, shows confidence and warmth; he'll surely make a fine Rossini Figaro very soon.

The factotum on this occasion, Björn Bürger, rattles off his famous aria with freshness, elegance and a fearlessness in the difficult range. Maybe he's a bit sexier than his new master, the Count Almaviva of Taylor Stanton (pictured right with guitar-strumming chorus), but the American has the perfect style of the true tenore di grazia in all his florid grace. Add two born comic troupers in Danielle de Niese's Rosina and Alessandro Corbelli, the best buffo alive, as Doctor Bartolo, and what could go wrong?

The answer has to be a director, Annabel Arden, who too often seems to have left the singers to their own devices. The start looks promising enough, a pretty balcony scene designed by Joanna Parker to conjure the Moorish element of Seville in a slightly more fantastical way than Christopher Oram for Michael Grandage's far funnier Le nozze di Figaro, returning later in the Glyndebourne season. Chorus and soloists are encouraged to direct a lot of their remarks out front to the audience and - especially - to Mazzola, who rises gamely to the comic interplay; that's all good. There are flamboyant Spanish dance-gestures, eventually overworked, and three actors serve to represent the commedia dell'arte origins of the stock plot.

Where does it go from there, though? Flailing gestures and loose business betray a lack of tight direction. De Niese and Corbelli can contort their lovable mugs beguilingly (the two pictured left), but the young master and servant need more help if this Figaro is not to appear smug rather than charming, and this Almaviva genuinely funny in his disguises to get at Bartolo's ward. Even the brilliant Janis Kelly in the cameo role of maid Berta is allowed too much licence, in a costume that's at loggerheads with the rest - period when, exactly? - and a dance routine for her arietta which seemed to delight many in the post-picnic audience but left me stony-faced, well sung though it certainly was (and Kelly gets the high notes in the Act One finale).

So when what you see in the ensembles doesn't match up with what you hear, energy can be dissipated. Take the climactic Act Two trio in which Figaro urges the eloping lovers to get on with it - crisp musical fireworks, nothing much going on (and those library steps served no purpose other than to give the singers somewhere to go, for no good reason). The inept staging which accompanies the storm music wasn't nearly as much fun last night as the downpour which burst on unsuspecting picnickers in the long interval.

Both act finales were fuzzy, wheeled- or flown-in harpsichords at the end of Act One (pictured below) not a meaningful enough distraction from the messy police-force business. it might have been funny to see Basilio (a cavernous Christophoros Stamboglis) begin spontaneously combusting in his slander number, but the smoke billowing from under the cassock somehow didn't define the conflagration well - and only needed to happen once. A good director doesn't need to keep repeating gags.

Mazzola just about freed everyone from this diffusion in Act One, but it was a mistake to turn the Act Two structure pear-shaped with an extra aria for Rosina (I think this was the one supposedly furnished by Rossini for Josephine Mainvielle-Fodor in 1819); better to have had Almaviva's "Cessa di piu resistere", too often cut as it was here. It's too late to make us feel genuinely sorry for this adaptable minx in her perplexity at having been seemingly deceived by her "Lindoro", and the number wasn't de Niese's finest moment; though she has all the coloratura at her disposal, and stitches an impressive chest voice on to her usual range, support came and went on the first night, with patches of under-the-note singing.

Easy enough to forgive that given her stage-animal presence and energy, but on this occasion neither she nor Corbelli, who should have been the real star of the show, had quite enough to work on. So many opportunities with a brilliant cast missed. Let's hope Laurent Pelly can do more with Béatrice et Bénédict, the other new production this season. 

• At Glyndebourne until 17 July