Opera: Il Corsaro Royal Opera House, London

Lord Byron wrote the poem but I doubt he'd have recognised the opera. We're talking here of Verdi's "galley years", where plot and music were more or less interchangeable, where what was good for the Israelites would do just as nicely for the Greeks or the Peruvians, where exotic was exotic whatever the location, on high seas or low lands, and the Italian "banda" tradition brashly held court in one trumpet-led unison after another. Il Corsaro is a pretty rum affair, full of eminently recyclable tunes (the furtive, lovelorn clarinet quick to make its appearance) and tremulous declamation. An overworked piccolo exults in its salty spray.

Half a handful of character-forming arias are probably worth preserving from its compact hour and 20 minutes of music, not least the tenor's Act 3 lament with its lachrymose viola and cello obbligato. The final trio portends Rigoletto. But the opera needs to be fabulously sung if it's to be worth exhuming for even a concert performance. And this miserable excuse for an evening couldn't even manage decent. When a sick tenor (for whom apologies are made) sounds appreciably better than those in good health around him, then you're in trouble, big trouble.

Jose Cura was that tenor, captain of the corsairs, heroically buckling his swash while discreetly expectorating into a ready handkerchief. He has quite a following among the Covent Garden cognoscenti - a tall, swarthy figure with a voice to match. The colour of that voice - grainy, dark- hued - is arresting. But it's one colour, one dimension, without the interest of an instinctive, inquiring musicality. And without the natural resonance to sustain long, grateful phrasings, were they ever to be forthcoming. He should work on his legato and leave the trumpettings to look after themselves.

But thank heavens for him. He alone sounded like he had any business on this stage - with or without the scenery. Roberto Servile (as Seid, his antagonist) might regularly pass muster in smaller houses further down the international league table, but his dry, anonymous voice was conspicuously below par in this context. So, too, the young Russian Viktoria Loukianets as Corrado's beloved, Medora. Now here at least was a singer displaying the kind of musicality so sorely lacking among the rest of the cast. A little precious, a little fanciful, perhaps, but sensitive, subtly inflected phrasings that actually meant something. What a pity, then, that the voice itself should be so anaemic - pale and uninteresting. All the colour, all the quality goes out of it in the lower dynamics. It all but disappears at anything less than mezzo-forte. A good vocal coach might yet find some body in it.

Maria Dragoni (Gulnara) has plenty of that - and one can just imagine how exciting a prospect she must have sounded before the ravages of a plainly mismanaged career took their toll. The husky, Callas-like timbre is all that remains now. Vocal endearments are no longer an option. She gets by on vulgar glottal stops, an overworked chest register, and pneumatic top notes. It's a voice in distress.

Which just about sums up the evening. Evelino Pid eagerly presided over a tired and overworked orchestra and chorus, springboarding into every jaunty, singalong accompagnamento in a fruitless attempt to kick-start the proceedings. One was grateful to have been spared a staging, but some of us would have welcomed the distraction.

n Repeated 7.30pm tomorrow (booking: 0171-304 4000), and live on Radio 3