It's a long ride through time and cultures from mid-17th-century Venice to late 20th-century Leeds; but with the lights down and a seething full-house at Opera North's Return of Ulysses on Tuesday it wasn't hard to think yourself back into something like the circumstances for which Monteverdi wrote the piece 350 years ago. Nor was it hard to believe that the values of this hybrid, part-historically aware, part-modern staging touch a basic truth about the piece. And the truth of Ulysses is that it, too, is an old-new hybrid: a reworking of established methods to attract new audiences.

When Monteverdi wrote it in 1640, opera was a still-emerging art which had only just made the quantum leap from private, courtly entertainment to public, commercial enterprise. The world's first general-access opera houses had opened in Venice three years earlier, and Ulysses addressed their possibilities and limitations. It was budget-conscious, less elaborate in its musical demands and more direct in its focus on telling a story simply but expressively. Above all, it presented human characters with real emotions. Gods and goddesses were there, but at the margins of the frame. New public opera aimed to show its audience their own (sung) lives.

And that's what the director Annabel Arden does at Opera North, in a production that handles Monteverdi with the care due to ancient artefacts but without turning him into a museum piece. Timeless ethnicity rubs shoulders with a touch of Paul Smith in the costumes. The set (by Tim Hatley) is an equally eclectic module of wood and gauze that divides the stage into an upper platform where Penelope can sit unpicking her embroidery and a lower area, looking like the beach under a pier, where you expect Peter Grimes to turn up any moment but actually get the pastoral, non-courtly scenes.

The set also provides separate platform areas for a small group of continuo instruments - theorbos, harp and keyboards - which are positioned to be visible but not distracting, and close enough to the singers to be able to accompany them intimately. It makes a more integrated performance than you get when stagings of Renaissance opera exile the continuo players to the pit. And although there are extra players in the pit, they are sparingly used. In stageworks of this period you get a choice.

The reason is that the priorities of early opera were literary. Words mattered and were preserved after the event (to be set again by someone else), while music was considered ephemeral and jettisoned. Few manuscripts survive intact, and even Monteverdi's special-case celebrity didn't protect Ulysses. All we have is a skeletal copy-manuscript written largely on two staves: one for the voice part and one for an accompanying bass line. From such slender evidence, latterday perfomers have to "realise" the score in much the way forensic scientists reconstruct images of the long- dead from surviving fragments of their wisdom teeth. And beside details of tempo, dynamic and harmony, the big question is: how do you allocate notes to instruments?

One thing we know is that Monteverdi had a flexible attitude to instrumentation. Most modern versions take that as licence to think big: from Raymond Leppard's gorgeously libertine realisations for Glyndebourne in the 1970s to those of Nikolaus Harnoncourt and Renee Jacobs, which are stricter on period style but still tend towards bold orchestral colouring with trombones, trumpets and the like.

Opera North's edition, made by its music director Paul Daniel, is the opposite: restrained and small, with nothing beyond the continuo instruments except solo strings, harpsichord and recorders. Conducted by Harry Bicket, it's pleasing but austere, and relies on the ability of the voices to create interest through the intensity of their singing. Monteverdi's long, declamatory recitatives were designed for just that purpose; but it's not easily achieved, and the Opera North cast have their problems. Some struggle with the exposure this kind of writing gives to any lapse of intonation. Others don't quite tease the declamation into life. But it's a strong company effort, with capable singing-actors throughout. Alice Coote's Penelope is cool - too much the dignified-but-troubled housewife in a made-for-TV thriller - but opens out for the final duet. As for Nigel Robson's Ulysses, you'd travel far to find a more committed or intelligently sung performance; and it's perfectly attuned to the kind of theatre Annabel Arden sets out to make. Small in scale but strong in impact. Nothing I've seen recently at Opera North has been so obvious or so encouraging a statement of what the company is about. Great voices, no. Great stars, no. But the will, guts and imagination to create events from slender means.

The Royal Opera/Elijah Moshinsky Otello has had some eventful casts in its 10-year history but not, alas, for the revival that opened on Thursday. Vladimir Bogachov rises periodically to the challenge of the title role but is mostly coarse-grained; Kallen Esperian, the new Desdemona, is unalluring; and Paolo Gavanelli's new Iago has a bleating dryness. The saving grace is the conductor Myung-Whun Chung, former MD of the Paris Opera and en debut (long-awaited) in the Covent Garden pit. He's oddly inconsistent: sometimes the attack is brilliant, sometimes (notably, the big Otello/Iago duet that closes Act II) it underachieves. But in broad terms his motivation of the score and enrichment of the orchestral sound is impressive. Less so is the time it's taking to make set-changes now that the ROH development is closing in on life backstage. Things can only get worse as D-day approaches.

Finally, two image problems. One belongs to Jean-Yves Thibaudet and is of his own making: a flamboyant platform style (not to say dress sense) that sells his playing short. You expect him to be a showman-pianist, and he does have an astonishingly fluent, off-the-shoulder kind of technique. But he's also musically substantial, rich in ideas and imagination; and his two recent appearances at the Wigmore Hall - by himself, playing Chopin and Debussy Preludes, and with the mezzo Angelika Kirschschlager in Viennese late-Romantic songs - made the point. Forcefully.

The other image problem concerned the London International String Quartet Competition which, after 20 years' distinguished operation, seems to have lost its steam and its ability to attract exciting entrants. By common consent, last Sunday's final was disappointing; and Monday's gala appearance of the winning Auer Quartet from Hungary was a qualified success. They played Mendelssohn's early A Minor Quartet with a fine sense of the beauty of the second movement but, otherwise, limited intensity and textural depth. The gala itself was an unatmospheric City- corporate affair, enlivened only by the Band of the Royal Electrical and Mechanical Engineers who shuffled on and off the Barbican platform (for fanfares) as though they had ferrets down their trousers. That this was the most memorable feature of the evening says something.

'Ulysses': Leeds Grand (0113 245 9351), Thurs & Fri. 'Otello': ROH, WC2 (0171 304 4000), Mon & Thurs, to 5 May.