Chamber opera - or, more often, pub opera - seems to be flourishing in London at the moment, with half a dozen companies actively putting on reduced productions. The latest of these to take place at my local theatre is Opera London's version of Il Trovatore, somewhat reduced down to two hours and performed with just a piano. The cuts were done reasonably cleverly - some whole scenes, some batches of a few bars - and mostly worked fine.

In the programme notes, Opera London reprinted Caruso's gag that "all that is needed for a successful performance is the four greatest singers in the world." It's a message that Opera London must have taken to heart, because they clearly took the trouble to find four singers who were thoroughly capable of mastering the demanding main roles. Canadian tenor Randy Nichol was the outstanding performer as Manrico: his diction was crystal clear while at the same time summoning up dramatic power. He would have been matched by baritone James Hancock but for a throat infection that seemed to strike him part way through the first act: Hancock's voice cracked badly during Il balen but he carried on heroically, obviously suffering but still managing to hang in there somehow. Both Helen Julie Johnson as Leonora and Mary-Jane de Havas as Azucena were on top of their roles.

But you can have great singing for Il Trovatore and still misfire - either from the point of view of a novice or of someone who knows the opera very well. The two biggest problems were ones probably unknown to Caruso: the translation and the piano. The translation was truly awful. For the majority of the lines, it didn't actually translate the Italian, choosing archaic English that was broadly along the same general direction of the aria but little more: one could forgive this if the words had wrapped themselves beautifully around Verdi's music, but that wasn't the case either. At the very beginning, I felt for Michael Storrs as Ferrando, trying to force an almost impossible text of Di due figli around Verdi's complex figures. If you weren't familiar with Il Trovatore, the translation made it very difficult to work out what was actually happening in an opera whose plot is pretty opaque to begin with.

I don't have a problem with chamber opera being played on just an electric piano; in a way, last night, this enhanced the opera by making you concentrate far more on the wonderful vocal harmony and counterpoint in Verdi's trios and quartets. But it needs a better combination of instrument, set-up and amplification than we had - there just wasn't the dynamic range or richness at the low end, and it sounded tinny on top. And it wasn't played well enough: the performance was filled with fluffs and hesitations. I'm sure it's a tall order to play two hours of Verdi straight through while keeping precision and verve throughout, but that's what the format demands, and it wasn't delivered.

The production premise - updating the original's Spanish Civil War of the fifteenth century to the one of the 1930s - worked well enough, and the small stage suits Il Trovatore's story-telling style. But the production lacked attention to detail. So why, when Leonora's servant Ines bids her a sad farewell as Leonora is about to take holy orders, is Ines dressed as one of the nuns? And we know that Azucena is a gypsy, but how can one dress her as Carmen with flowing golden curls when she's supposed to be a frightening old witch and Manrico's mother? And how can we believe in Ferrando, who is supposed to be old enough to have been a guard when Di Luna and Manrico were babies, when no stage make-up has been used and he looks young and dashing?

Il Trovatore has overwhelmingly more than its fair share of memorable opera tunes. Opera London gave us a perfectly good chance to listen to them all, generally sung very well. But details matter, and I felt that it could all have been much better if more care of them had been taken.