Wagner just won't box clever

I've always rather liked this time of year, but this week I woke up convinced that I was suffering from Seasonal Affective Disorder. I felt heavy, low, and anxious. Sad. I was all set to go out and buy one of those visors that make you think it's sunny when one of my less holistic friends phoned up. I explained the problem and told him where I'd been and what I'd seen. "Ah," he said, "I'm not surprised. What you're suffering from is Tristan and Isolde Reactive Energy Drain."

I've always rather liked this time of year, but this week I woke up convinced that I was suffering from Seasonal Affective Disorder. I felt heavy, low, and anxious. Sad. I was all set to go out and buy one of those visors that make you think it's sunny when one of my less holistic friends phoned up. I explained the problem and told him where I'd been and what I'd seen. "Ah," he said, "I'm not surprised. What you're suffering from is Tristan and Isolde Reactive Energy Drain."

Well, there are worse things you can do for six hours than listen to Wagner's Tristan. The music is astonishing - beautiful, inexorable, detailed, voracious of attention - but so it should be, at three times the length of Carmen and five times the length of Dido and Aeneas. Being swallowed up into a single work for that length of time (particularly one so central to a composer's efforts to re-shape an entire art form) is an unnatural and exhausting experience. It's best undertaken in your own home, lying down in the dark, where you can forget about the problems of staging an opera in which hardly anything happens, and fill in the blanks yourself.

Sitting in a narrow seat for the length of a transatlantic flight, in the knowledge that at the end of that time you will be somewhere sunnier or more glamorous or at least different, is all very well. Especially when there are little bags of peanuts to distract you from looking at your watch. The optimum approach to Tristan is to surrender; to lie back and think of Germany - or, in this case, the ancient Cornwall of Wagner's imagination.

Like Parsifal, Tristan attracts a degree of semi-religious fanaticism, and a quite different audience to Der fliegende Holländer or Die Meistersinger von Nürnberg, what with the comparatively brief length of the one and the discernable narrative of the other. The fully-fledged Wagnerite expects transcendence, so I wasn't too surprised by the heavy breathing, the glistening brows, the strange clothes and the swooping, slow-tempi conducting - all of these from the stalls, by the way. But at the end of this particular journey we were exactly where we had started: scrunched up in front of two very large primary-coloured Portakabins.

Director/designer Herbert Wernicke's staging was like a mobile strip-club decorated by Braque and Mondrian. Each cabin was stuck through with the kind of slippery steel poles associated with lap-dancing (though this being Covent Garden and not ENO they were not employed for that purpose) and contained a comedy parody of a Wagnerian singer: short, round Tristan (Jon Frederic West) in the frumpy, weather-girl royal blue cabin, and big, rectangular Isolde (Gabriele Schnaut) in the chat show scarlet cabin. And there they stayed.

Given the material Wernicke had to work with, maybe boxing in the singers wasn't such a daft idea. Tristan is about narcissism (each lover is more interested in their own response to passion than in the object of that passion), and Schnaut and West are not exactly balletic - so what better to do with two singers who don't know how to move than stick them in two boxes that can do the moving for them? But there was not even a chink for a Pyramus and Thisbe kiss. The only prop was the goblet for Isolde's magic potion, so, give or take the Everyopera costumes (vaguely Mittel-Europe, vaguely fin de siÿcle) and West's amusingly futile search for his fatal wound in the last act (pinning the tail on the donkey came to mind) the Portakabins were all we had to look at. Sure, we saw them tilt a bit (to represent the sea journey), we saw them move forward, go away again, and sidle up to each other (to represent illicit yearning), in the third act we even saw them swap places, but that was really that. Two boxes on wheels. For six hours.

Musically, there were compensations. Bernard Haitink's conducting was as impressive as ever - thoughtfully and painstakingly exploring the construction of the opera. Petra Lang was a warm Brangäne and Peter Rose gave a beautifully shaded performance as King Marke. And the orchestra played faultlessly from the first filmy notes of the prelude to the grand sweep of Liebestod, responding to the concentrated quality of Haitink's interpretation. I only wish I could have heard his Tristan und Isolde without this Tristan or this Isolde but, with an 85-minute duet for a second act, it was hard to ignore the flat, smack-in-the-face, Shanghai-opera-on-steroids sound of Schnaut or the neurotic, Broadway vibrato of West.

I'd love to be able to write a glowing review of this production for the orchestral playing alone, but I simply can't. Wagner termed Tristan "music-drama", and with Schnaut and West as the leads it fails on both counts. The performances of the supporting cast demonstrate that it is reasonable to demand more than just a very loud voice from Wagnerian singers, so I wonder how long this type of casting will prevail.

That Wernicke's design was jeered was no surprise. With an opera of this length you want scenery, landscapes and ships. You want passionate embraces. You want animals and crowd scenes, sumptuous costumes and gratuitous special effects. In this production, you just want Isolde to bloody well drink the right potion in the first place and die at the end of Act I.

Of course, what I think about Covent Garden's Tristan matters not one jot. This isn't Mozart or Britten or Birtwistle, and floating voters are rare when it comes to Wagner. Die-hard enthusiasts will always go, no matter how excruciating the singing. The gentleman to my right was in visible agony during Isolde's Liebestod. He knew exactly what to expect having heard - and hated - Schnaut at Bayreuth, and he still bought a ticket. If there are any waverers out there, the best advice I can give is to listen to BBC Radio 3's live broadcast on 9 November while studying a large lava lamp. It's cheaper, you'll get the general idea, and at least you'll be comfortable.

'Tristan und Isolde': Royal Opera House, London WC2 (020 7304 4000), to 9 November