MUSIC / Touched by genius: Composer or conductor, gay or straight, maestro or maverick - who exactly was Leonard Bernstein? Edward Seckerson asks his latest biographer

Unitel were in Israel on the last leg of their Leonard Bernstein / Mahler project. A decision had been taken to film only three of the four live performances of Das Lied von der Erde so as to conserve enough raw footage to cover an additional recital. But, according to Bernstein, the best performance of the week was - you've guessed it - the very one they didn't cover. Now picture the scene. At a farewell party in his honour, Bernstein publicly rebukes the director concerned: every minute of every performance should have been filmed. 'Unrealistic and self-indulgent,' replies the director. Bernstein glowers: 'Well, if that's what you think, you can just fuck off.' Matching expletive with expletive, the director, blind with rage, turns on his heels, walks straight into a plate-glass window, and knocks himself out. Next day, the two men go surfing together in Tel Aviv harbour.

Humphrey Burton was the director with the smart line in dramatic exits, but his name is nowhere to be found on this or any other of the first- hand anecdotes contained in his major new biography of the great American conductor and composer. After some 30 years of working with Bernstein, after numerous TV projects, including six specifically biographical programmes, he felt it important to maintain some degree of distance. Tricky, when your subject was both friend and colleague and you've just spent the best part of three years sifting through his most intimate personal effects. The Bernstein Estate gave Burton unprecedented access to letters and papers, date-books, scrap-books, most of them preserved now on microfilm. Bernstein was 14 when he started pasting up his cuttings. How's that for precocious. Humphrey Burton reckons he was already aware of his place in history.

Burton's first draft came in at 1,850 pages. Now there are 600. Incisive editing was always his priority in television, particularly when supervising other people's work. This was different. Every cut was the unkindest. But necessary. 'I needed my editors to look out for clarity and narrative drive. Actually it was a bit like working on 200 TV programmes simultaneously - each chapter was a programme in itself. I had a file on every Bernstein composition, a card index of prominent associates, over 250 taped interviews, a master calendar telling me exactly where he was, when and why, for every year of his life . . .' First for the blue pencil was a surplus of musical commentary and analysis: Bernstein, the composer, as others heard him. The book was getting top-heavy. 'I was anxious to make sure that the music was felt and experienced as part of him and his life. Because that's the way it was. He lived through every aspect of music.'

There were other losses. Among them, a sequence of letters which very much intrigued this reader when offered a preview of some proofs by the author. They concerned one Charlie Roth, a young would-be conductor with a Bernstein fixation. No one knows the full story, but during the 1950s Roth became a nuisance, hounding Bernstein, repeatedly popping up like the black fairy - Lenny's 'dark side' coming back to haunt him.

Now we're heading into Joan Peyser territory. Her infamous 1987 biography doesn't bear much scrutiny, as Burton quickly discovered. Peyser's muck-raking (in fact, she spent all of one day with Bernstein) drew much of its sustenance from amateur psychology with a homophobic slant. For Burton, the psychology was always in the documentation - the man's words and actions, his letters, his shared confidences and, of course, his music. 'I wasn't a deep intimate to Lenny's private tragedies and angst, but like anybody else I could read between the lines.' Burton's book may have the 'approval' of the Bernstein Estate, but it isn't 'authorised' in any censorial sense. Bernstein's sexual ambivalence is told like it is. And the more that is revealed, the more the word 'bisexual' begins to sound like a euphemism for 'gay family man'. Guilt led to denial in a famous heart-to-heart confrontation with his daughter Jamie, yet at her wedding he welcomed the groom into the family boasting: '. . . and he's straight]' Only Bernstein could have startled the Tanglewood canteen singing 'Everybody out of the closet' to the tune of Tchaikosky's Fifth and then, in a darker moment one night in Vienna, written the following verse to one of his male friends: 'Today is my free day; What shall I do? / I do not want another thousand kisses / Na, Ja, Vielleicht fahre ich in den Prater / and kiss at length one pure and total stranger.' As Burton adds: 'It is the Marschallin in Der Rosenkavalier who goes riding in the Prater after sending her lover away.'

That one verse is worth a thousand interviews. For Burton, it was one of many good reasons for standing back and allowing the documentation to speak for itself. In some cases, he discovered, even Bernstein's own claims were sharply contradicted. Chronology revealed that it was Aaron Copland, not Dimitri Mitropoulos - as Bernstein always maintained - who first set him on the path of conducting; and, in the light of the whole story, it was now possible to set the record straight over Bernstein's relationship with his father. Bernstein was apt to exaggerate the extent to which his father had discouraged his musical career. Why? 'Because,' says Burton, 'Lenny liked a good story.'

Lenny was a social, musical, spiritual eclectic. He wanted things every which way. He wanted to be all things to all people. To be loved by all. Even Burton, it seems, was sometimes uncomfortable with what he now refers to as the 'messianic' factor: the idea that he was changing people simply by reaching out and touching them (particularly in Israel); the way in which he would ritualistically hold court after every concert - a kind of surgery. 'He knew full well,' says Burton, 'the power he had - and he gave of himself unstintingly. The laying-on of hands was, in a kind of mental way, part of the process. He needed that. He needed the adulation, the electric circuit between him and his audience . . . He needed the drug called 'baton'.'

Which is partly why he never could resolve the lifelong conflict between conducting and composition. His head was full of unfinished pieces: 'Plenty of acorns,' says Burton, 'but a bit short on mighty oaks.' It was almost as if he were afraid to commit more time to composition. Burton accepts that he was probably more insecure about it than we will ever know. It hurt him deeply that his peers (including his beloved Copland) never really took him seriously as a composer. Milton Babbitt actually laughed in his face over Chichester Psalms. Tunes in C major? Heaven forbid. Bernstein once said of his conducting that he always knew how good a performance had been from the extent to which he felt as if he were composing the piece as he went along. Burton reminds us that his most productive times as a composer were those close to, and beyond, deadlines. There's something in that. You feel the rush of his finest moments: like the song about the writing of a song in the 'Sanctus' of his masterpiece (in my judgement), Mass, where the tune really does 'take wing and rise up singing'.

Burton's finest moments are those which spirit us behind the scenes: the five minutes between movements in Mahler's Eighth Symphony, during which a whole team of acolytes would duly spring to the maestro's every need - his change of clothes, his cigarette, his cologne. And, of course, the many treasurable anecdotes. Like the telegram that arrived when Bernstein was due to meet the Pope. Mindful of his reputation as an inveterate kisser, it read simply: 'REMEMBER: THE RING NOT THE LIPS.' At Bernstein's funeral, his brother spoke of how hard it was to accept that someone who had 'always been larger than life, turned out to be smaller than death'. But reading this amazing story, and listening again to his finest pieces, pieces like Serenade and Songfest, I'm not so sure.

'Leonard Bernstein', Faber & Faber ( pounds 20)

(Photograph omitted)