Like a grand old dowager in straitened circumstances, the Royal Opera House summoned all the dignity she could muster for her last night out on Monday, dusting down the faded party frock and walking carefully to hide the moth-holes. Slowly, poignantly, and just a touch pathetically, the curtain lowered to the strains of Sleeping Beauty; and we all left wondering what the Prince would find when he arrives with that awakening kiss in two years' time (or three, or four...). Miraculous rejuvenation or a withered corpse?

For those who don't have TV or read newspapers, and who weren't among the great and good of British society in attendance, I should explain that this was the Farewell Gala with which the House closed down until - er - however long it takes to dismember and rebuild it. Officially it opens with a Falstaff in December 1999. But who knows? It's a massive project and beset by controversy. Anything could happen; and with Covent Garden's luck, it probably will.

The first problem, of course, is the money, which has been a matter of public debate ever since pounds 78.5m of lottery cash was promised back in 1995. Outrageous, screamed the press. Money for toffs. And What About the Homeless? - as though the homeless were in competition for the money or losing out on something that might otherwise have been theirs, which wasn't the case. Social need was, and is, a separate category of giving under the lottery rules. That pounds 78m had to go to the arts; and although it seemed a vast amount, in fact it only covered a fraction (37 per cent) of the total redevelopment costs, which are currently set at pounds 214m. The difference has to be raised by private giving and property deals; and that's another of the many question-marks hanging over the length of closure.

The one unarguable thing is that the work is badly needed. The Opera House is a national institution and part of the cultural stock by which this country's claim to civilisation is measured in the world. For years it has been grossly underfunded - which is why the building (and the companies it houses) are in such a mess. The redevelopment will bring its backstage facilities into the 20th century (just in time!), and enable the companies to work with some semblance of efficiency, increasing the number of performances by 15 per cent.

With vastly improved public access (especially for disabled people), air-conditioning (hurrah) and two small-scale performance spaces, it also will accommodate 20 per cent more people and feel far less like a members' club. All these things can only be for the good.

But that said, there was an inevitable atmosphere of sadness on Monday. We were saying goodbye to a regime which, for all its muddle and nonsense, is part of many of our lives. What's more, we were effectively saying goodbye to a number of artists, much-loved, whose careers will probably be over before the House is back in business.

It would be invidious to name names; but one unequivocal example was Heather Harper who came out of retirement for this Gala to sing a snatch of Ellen Orford - the Britten role which was so wonderfully hers - for one last time. It was profoundly moving; and I'm sure I'm not the only soft touch in the audience who shed a tear.

I just wish I could say that the Gala was as memorable for its artistic quality as for its sentimental appeal. But I can't. Galas are wretched things at the best of times: conveyor belts of loose ends that accumulate with a surreal unease. And this one, playing to audience of operaphiles and balletomanes with mutual distrust of each other's passions, was peculiarly uncomfortable. Sandwiched between slices of danced Ravel and Mendelssohn, the pub scene from Peter Grimes (fully staged from the Elijah Moshinsky production) ran like old-tyme Sadlers Wells slapstick. Maybe it was meant to be a period performance. Subsequent vignettes of Arabella, Rosenkavalier, and La Boheme were even ropier; and I could have choked when someone asked me afterwards if these things had been chosen to reflect the Opera's greatest triumphs of recent years.

There have been triumphs: the Meistersinger, the Ring Cycle (as music), the Mathis der Maler (ditto). But to pull together excerpts from these on the last night of its current life was more than the poor old House could manage. Instead, it leant on the loyalty of a handful of British stars (Felicity Lott, Tom Allen, Anthony Rolfe Johnson...) capped with a token appearance by Placido Domingo. And that was it.

But in fairness, Domingo sang superbly, as did two of the younger British stars who should surely be around and in their prime whenever the House reopens: Bryn Terfel, snarling his way through Iago's Credo from Otello, and Anthony Michaels-Moore, distinctly eloquent in the Act II sextet from Lucia di Lammermoor. Neither artist has as yet appeared in these operas at the Garden; so there, at least, is something to look forward to.

The conductors, meanwhile, came like a relay race, passing the baton from hand to hand. And as Solti, Haitink, Downes, and Colin Davis took their turns with a platoon of lesser, ballet-conducting names, it was a lesson in the way the chemistry of personality affects orchestral sound. It also reminded me why I rarely go to classical ballet - because the same musicians who play like gods one moment for a cast of singers tend to play like animals the next for a cast of feet.

But there it is: for better or worse, the House we knew and sometimes loved has gone, and its going has roused strong emotions. Not least from its own staff who have lost their jobs and, with nothing else to lose, took the end of this Gala as an opportunity for minor sabotage. As Solti, Domingo et al tried to take their bows, they were upstaged by stagehands marching back and forth in front of them with Victory salutes. Then, as the royal party were about to leave, a front-of-houseman surfaced in a box and made a desperately embarrassing unscheduled speech. It was regrettable but understandable: a semi-insurrection. And it left a sour foreboding that however long this Beauty sleeps, it won't be peaceful.

Presenting the Gala for television was Michael Berkeley, taking a night off from one of his (many) other lives as artistic director of the Cheltenham Festival; and an inspiring festival it's been this year, refreshed by Berkeley's policy that every programme should contain some music Of Our Time. It clearly hasn't been easy for all his artists to comply with that demand, especially the period performance bands. But last weekend the Orchestra and Choir of the Age of Enlightenment slipped a new, attractively accessible choral work by Betty Roe, His Winding Sheet, into their otherwise immaculate all-Bach concert; the pianist Piotr Anderszewski prefaced his Bach and Beethoven recital with some elegantly decorative Preludes by Lennox Berkeley (Michael's father); and the BBCSO under Markus Stenz completed a Brahms and Mahler date with a substantial new commission from Vic Hoyland called A-Vixen-A.

The explanation for that name is complicated and seems to me of little relevance to anyone but the composer. The music is comparatively straightforward: a slow, grandly envisaged circumnavigation of a fixed idea - namely an angular, uneasy trumpet melody that surfaces through changing textures with the insistence of Charles Ives's Unanswered Question. And the question here is whether there's enough to sustain five movements with a combined duration of more than 30 minutes. But the handling of orchestral colour is strong enough to hold attention in its own right. We were not bored.

And no one could have been bored by the Anderszewski recital, for similar reasons. Anderszewski's playing is supremely wilful, sometimes overestimating what it takes to make a point and, to my ear, unidiomatic, in Bach. But the sense he gives of an explosive energy, only just contained by the formalities of stylistic decorum, serves him well in Beethoven; and at Cheltenham he delivered the Diabeli Variations with intelligently driven power - especially in moments of high drama like the transition from Variation 32 (a heavy fugue) to Variation 33 (a Mozartian minuet). Not many pianists give you muscle and imagination in so striking a relationship.