OPERA / Part of the scenery: Iphigenie en Tauride - Royal Opera House

In staging an old opera based on a still older story there are two possible avenues of authenticity. Does the producer attempt to re-create the characters and their world as historians know them now or as the composer and his audience knew them? Opera Factory's recent L'incoronazione di Poppea tended towards option No 1: Nero's Rome as we see it, rather than as Monteverdi might have reinterpreted it. Alain Germain's version of Gluck's Iphigenie en Tauride went all out for option No 2: costumes and scenery based firmly on original designs, with action stylised along 18th-century lines.

Visually, this new Iphigenie - performed as part of the English Bach Festival at Covent Garden on Sunday - was almost uninterruptedly delightful, and there was the added pleasure of feeling spectacle and music working in a kind of stylistic symbiosis. No matter that now and again a hint of affectionate irony surfaced in Germain's realisation: that only added freshness. What did matter was the way that, at best, sights and sounds supported and enriched each other. The numerous ballet scenes, with their sumptuously plumed soldiers, white- robed priestesses and elegant furies, were a treat for eyes and ears. One slight puzzle - why these magnificent neo-classical apartments were so scantily furnished - was soon solved: the cast themselves were the furniture; anything barring peripheral columns or the odd carefully placed folding chair would have been clutter.

As for the sounds: there is something about the contrast between the willowy, whispering tone of the 18th-century flute and the keening of the contemporary oboe which sounds in itself like a commentary on the production's forms and colours - especially when manipulated by a master- orchestrator such as Gluck.

Perhaps the string sections, or at least the violins, could have been larger. Occasional cracks and flutters might have been more effectively camouflaged, and the improved carrying power would almost certainly have benefited those of us who listened fron under the canopy in the stalls circle. But under Marc Minkowski's direction, the playing of the English Bach Festival Baroque Orchestra was on the whole as fresh as the spectacle. Not only were the colours projected beautifully, but the drama of the opening storm scene and the pathos of Iphigenie's Act 3 soliloquies owed a lot to their contribution. Any doubts about the power of Gluck's writing were quickly dismissed.

It was in the vocal contributions that problems arose - not in Jennifer Smith's dignified and expressive Iphigenie, nor in Donald Maxwell's blustering Thoas (a little strained at the top of the register, but generally commanding), but in the two male leads. Andreas Jaeggi's Pylade wasn't ideally steady throughout, and the effort he appeared to put into expression was by no means always apparent in the sounds he produced. Russell Smythe's Oreste was a bigger disappointment, so often sharp that at times one wondered if he might be trying to make a protest on behalf of modern 'inauthentic' pitch.

The dungeon scene, where the two men attempt to comfort each other, was nothing like as affecting as it should have been. The sudden appearance of a yellow balloon, drifting with the stately ease of Germain's dancers across the stage and into the pit, was a fine piece of apparently unintended critical comment. Nothing, however, spoiled the final coup: a cunning piece of trickery whereby Amanda McMurray's Diane seemed to step out of the scenery from behind the altar - just about the best example of Diva ex machina that I can recall.