Royal Concertgebouw Orchestra/Haitink, Barbican Hall, London<br/>The Genius of Mozart/Mozart Uncovered, BBC 2/BBC 4<br/>Radamisto, Royal Festival Hall, London<br/>The Magic Flute, The Coliseum, London

A glimpse of what might have been

For conductors lucky enough to make it to their 70s in good health, it is a precious decade. This is the decade when a lifetime's influences and ideas coalesce, when new thoughts and techniques make their last brilliant entrance, when knowledge supersedes showmanship and the world's greatest orchestras move to their maestro's side like mountains to Mohammed. For an audience giddy with the Indian summers of several outstanding septuagenarians, these are precious years too. These are the years when certain performances achieve an impact that you hope never to forget: Davis's Peter Grimes and Les Troyens, Mackerras's Brahms 1, Abbado's Parsifal and, now, Haitink's Bruckner 9.

For conductors lucky enough to make it to their 70s in good health, it is a precious decade. This is the decade when a lifetime's influences and ideas coalesce, when new thoughts and techniques make their last brilliant entrance, when knowledge supersedes showmanship and the world's greatest orchestras move to their maestro's side like mountains to Mohammed. For an audience giddy with the Indian summers of several outstanding septuagenarians, these are precious years too. These are the years when certain performances achieve an impact that you hope never to forget: Davis's Peter Grimes and Les Troyens, Mackerras's Brahms 1, Abbado's Parsifal and, now, Haitink's Bruckner 9.

Last weekend, nearly 50 years after his professional debut, Bernard Haitink began his 75th birthday concert series at the Barbican with the Royal Concertgebouw Orchestra: the orchestra he grew up listening to, the orchestra of which he was Principal Conductor for 24 years, the orchestra of which he is now Honorary Conductor - a role created to acknowledge their life-long connection. The faces of the players may have changed. (Like the Berliner Philharmoniker, whose contribution to "Haitink at 75" takes place in September, the Concertgebouw is now a young orchestra.) But the technique, sensibility and sound remain exceptional: smooth, refined, vibrant and deliberate. A finer palette for an an old master like Haitink is hard to imagine. Too rich for Mozart perhaps, but of perfect scope and subtlety for Bruckner's final, unfinished symphony.

This is a paradoxical work. Reflection, doubt, tenderness and acquiescence - the final movement's extended "Dresden Amen" - frame an implacable, mechanistic scherzo that, more than any of Mahler's neurotic symphonic prophecies, heralds the industrial-scale carnage of the First World War. In Rattle's hands in September 2002 at the Royal Festival Hall, the scherzo was an Expressionist hail-storm of splintered bones. A judgement-day nightmare that decimated the high-vaulted ecclesiastical structure of the first movement. In Haitink's it was organic, private, taut, slow, restrained, regretful, guilty: a cruelly curdled distortion within a clean Romantic super-structure and quite the most terrifying thing I've heard in a concert hall. If Mahler's Ninth (with the Vienna Philharmonic), Sixth (with the LSO), and Third (with Berlin) Symphonies are as compelling as this, Haitink's 75th year may well be his finest.

As Haitink's Mozart with Andras Schiff seemed stiff in contrast, it was interesting to catch the same concerto (K466) played so vivaciously by fortepianist Ronald Brautigam on BBC 2 and BBC 4's The Genius of Mozart and Mozart Uncovered. Did you know that the slow movement represents Mozart's desire to return to the nursery? Me neither! Setting aside presenter Charles Hazlewood's imaginative psychoanalysis of the score and the toothless colloquy of interviews-to-camera with Nannerl, Constanze and Leopold Mozart - a retrograde step after the wonderful Eroica - both programmes offered one extremely exciting thing: the best period instruments performance of Mozart by a British orchestra, period. The Mozart Collective (aka Harmonieband, depending on which part of the BBC website you visit) was formed ad hoc for the series and is not, as yet, a full-time operation. When or if it is, Britain can finally offer some serious competition to the Orchestra of the 18th-century in this repertoire.

Relative youngster William Christie, whose 60th birthday it is this year, flew into town this week for a semi-staged performance of Radamisto. Not, alas, with Les Arts Florissants but with Zurich Opera. Zurich have treated London to some rather lovely Wagner of late but are not - on the basis of the one and a half exasperating Acts of Radamisto that I could stomach - quite so proficient in Handel. Christie is a regular guest in Zurich, conducting both Baroque and Classical opera, and the house orchestra are so tickled with period style that they've formed their own gut strings band, La Scintilla. Unfortunately, their lack of fluency by comparison with those who play period instruments full-time was evident from their tone, their note-endings, and the car-crash of a cadence that left no space for the soloist's cadenza in one aria.

The singing likewise revealed stylistic unfamiliarity. I'm all for immediacy in recitativo secco but shoutiness? And then there's the Italian. With aggressively rolled rs splattered across the final consonants of words such as "cor" and "amor" this was an uncouth performance, with gestures - flouncing, shrugging, stamping, hand-jiving - that undermined the sincerity and rhythm of the music. Only the bare bones of Christie's style could communicate here - the swagger, the confidence, the superb balance of tempi, the long, beautifully punctuated phrases - and none of the ravishing details that fans of his work with Les Arts Flo and the Orchestra of the Age of Enlightenment have come to expect from this most punctilious of Handelians. Somewhere in this galumphing production is a subtle, sensuous score. In Marijana Mijanovic's expertly sculpted Ombra cara we caught a glimpse of what might have been. But if Christie can't secure the aesthetic, I don't know who can.

More Mozart now, in the umpteenth revival of Nicholas Hytner's production of The Magic Flute: still charming, still touching, still funny and - with the best playing and singing I've heard from ENO for a very long time - still a hot ticket. Crediting the wonderful boys, ladies, armed men and dancing bears individually would take more space than I have here but special mention should go to conductor Nicholas Kraemer, Carolyn Sampson (Pamina), Toby Stafford-Allen (Papageno), and Toby Spence: an elegant, stylish, sweet-toned and sympathetic Tamino. At last a revival that lives up to its name.

'The Magic Flute': Coliseum, London WC2 (020 7632 8300) to 16 April

a.picard@independent.co.uk