They say you shouldn't believe everything you read, and sometimes they have a point. Arriving in a remote West Country village armed with a house name but no directions, I blithely believe I will track down John Tavener from the George Harrison-style mansion and row of Bentleys outside. The newspaper cuttings describe a millionaire who has hobnobbed with the Beatles and Prince Charles, a perma-tanned giant who collects luxury cars, dresses like a rock star, and manipulates the press, the public and the content of royal funerals on the scale of a latter-day Machiavelli. Can't be hard to find a man like that in a tiny Dorset village.

They say you shouldn't believe everything you read, and sometimes they have a point. Arriving in a remote West Country village armed with a house name but no directions, I blithely believe I will track down John Tavener from the George Harrison-style mansion and row of Bentleys outside. The newspaper cuttings describe a millionaire who has hobnobbed with the Beatles and Prince Charles, a perma-tanned giant who collects luxury cars, dresses like a rock star, and manipulates the press, the public and the content of royal funerals on the scale of a latter-day Machiavelli. Can't be hard to find a man like that in a tiny Dorset village.

I ask at the pub. Blank looks all round. "Oh, you must mean Sir John," says a man. "But his house isn't as big as all that." I follow his directions back down the lane to the drowsy little church, almost suffocating under a foam of May blossom, winkle my car down a narrow track by the side, and waste 10 minutes trying to gain entry to the padlocked garden of a large brick farmhouse, before a gardener kindly informs me I'm barking up the wrong tree. Sir John lives at the more modest place next door attached to shambolic stables, the ground strewn with abandoned children's bikes.

"I've no idea why they do it," says Sir John, shaking his head over the fictional Bentleys (although there is one, it transpires: a G-reg, wheeled out once a year) as he ushers me to the garden. "Vicious, they've been about me - the music critics especially. I can only think they lead unhappy lives. Is that it, do you think?" Well, possibly. But touched as I am in his faith that I am not another of these wilful fantasists, I would suggest two gripes are at work, and it's useful to distinguish between them.

The lifestyle exaggerations clearly stem from a general glee over a man who fits nobody's idea of what a serious composer should be, whereas music critics are suspicious of the man's near-emetic output and riled by his refusal to toe the modernist line. Though Tavener did toy with serial techniques in his early years, no one has quite forgiven him for turning up to an SPNM weekend (the Society for Promotion of New Music) and suggesting that, rather than listen to the latest piece by Xenakis, they'd be better off with the The Marriage of Figaro. "At least Mozart knew how to write a vocal line," was his parting shot.

He is most famous for The Protecting Veil, a cello concerto which became a chart-topper on the launch of Classic FM. Then his Song for Athene was performed at Diana, Princess of Wales's funeral, thus granting an exposure (and boost to CD sales) most composers don't dare to dream of. His place in the public consciousness was assured, and the flow of music has barely stinted.

He writes with scant regard for normal musical resources or ordinary human comfort, yet the next four weeks will see no fewer than five Tavener world premieres around Britain and abroad, plus a revival at St Paul's cathedral of an early work extravagantly scored for 10 trumpets and four sets of timpani positioned at the north, south, east and west ends. What's more, The Veil of the Temple, last year's all-night meditational choral marathon - widely viewed as the grooviest happening to hit the London music scene since the Sixties - will get a second airing in New York this summer, plus a new two-hour version at the BBC Proms.

Perhaps what is most galling of all to contemporary music hardliners is that Tavener, at 60, is one of the few living classical composers whose music is listened to for pleasure by everyone from housewives to royal highnesses.

Its slow-moving chords and monastic chants have drawn the jibe "simple music for simple minds", but Tavener provokingly refuses to accept this as an insult. He sees his music's stasis as an antidote to the over-intellectualised, aggressively masculinised art of Western society. And though his pencil scores extend vertically over 24 staves and sometimes as many as 38, he prizes simplicity and innocence, and believes that if a composer can't hear the concerted sounds in his head as he's writing them, he shouldn't bother.

"A Greek friend once told me that if it's any good, you can sing it. And I think that's largely true. This is my problem with so much modernism, that you can't internalise it. And I somehow doubt that most composers can even play their scores at the piano. They haven't the talent. I can still play Mozart piano concertos - only for my own pleasure now - but I do think to be truly musical in that way is important. Of course there's a place for mathematics in music, but it can't be just mathematics. Webern is the only one who was able to work with serial procedures and produce mystical music. You can play it like Schubert, it's just so beautiful. But if we're talking Western musical heroes, there's no one can touch Mozart. That innocent, paradisical sound is quite unmatched. I can explain Beethoven, I can explain Bach, but I can't explain Mozart. It's just so simple and spiritual." But wasn't Mozart, by all accounts, rather profane in person? "One has to say that God is infinite," he says, "and these things come out all over the place."

Tavener and his relationship with God is another thing that raises critics' hackles. Believing in God, espousing the Greek Orthodox faith and even making a chapel in your garage is one thing, but seeking out Sufi spirit guides and Native American medicine men puts him well beyond the pale according to the sceptics. I don't get round to asking about the Sufi (though the composer's study shelves are dotted with formal photographs of a mature Indian lady) but the medicine man's visit is readily explained. He came as an unexpected add-on, Tavener says, with the delivery of a North American Indian pow-wow drum that he'd asked a musicologist friend to procure. There it sits in his study, the size of a large coffee table, and its deeply resonant boom - a wave of sound, rather than a beat - has brought about what the composer describes as "an eruption of creativity" in him since he acquired it last year. Not only does the instrument feature in six new works, but its very presence, Tavener believes, puts him in touch with "something truly primordial, a thing that Christianity seems to have lost." He hadn't expected an American Indian with hair down to his waist to arrive with the drum to demonstrate it. But it wasn't even as simple as that, Tavener says. "He wouldn't play till he'd stroked it and asked a blessing from the four-leggeds who'd supplied the doe-skin. And when we sat down to a meal, first he gave thanks to the four-leggeds for the gift of the meat and thanks to the earth for the vegetables. It was awesome, that sense of connectedness. It's what we so lack now."

With his great shaggy brows and flowing hair the composer would look the classic hermit were it not for his Persil-white trousers and crisply ironed dress shirt, carefully unbuttoned at neck and cuffs (though you notice his blue plimsolls still bear the little plastic tag). He talks quietly, and rather plummily, on matters of personal belief - that we are nearing the end of a Hindu time-cycle, hence the dregginess of today's culture; bemoaning Christianity's insistence that you can only be saved through Christ ("it turns God into a monster"). As he talks he resembles some great benign vulture, constantly shifting his hyper-extended limbs, flapping his cuffs and leaning his great beaked head forward, in the manner of those used to having to stoop to hear and be heard.

For Tavener is not just tall. He is six-foot-five. And his height isn't just hereditary, it's a symptom of Marfan's disease, a condition of the connective tissue. Abraham Lincoln had it, as did Rachmaninov, the composer famous for his enormous pianist's hands. Tavener's two young daughters have it too, though fortunately the symptoms are less severe in females.

While Tavener père now jokes about being able to perform party tricks with his loosely jointed fingers, the associated heart problems once brought him close to death, and it was this experience, largely, that turned his life and work around.

Having had a minor early success with The Whale, an oratorio based on the Jonah story recorded on the Beatles' Apple label, the young composer was briefly the toast of the Swinging Sixties. But he was not happy. He drank heavily, and his first marriage - to a Greek dancer with the Royal Ballet - lasted only eight months, partly, one suspects, because of his attachment to the parental home, where he lived with his ailing mother, Muriel, until he was 40.

But the marriage had introduced him to Greece and the Orthodox church, which he embraced with enthusiasm, while still drinking heavily. On the death of his mother he thought he'd never compose again, and it took the illness to unblock him. In 1990, depressed and in Greece, he heard his heart thumping loudly. Shaken, he went straight to the heart specialist Magdi Yacoub, who confirmed a leaky valve. At the same time a tumour was diagnosed in his jaw, so two operations were needed. Both were successful, and suddenly writing music became easy, leaving Tavener convinced that both illnesses had been sent by God, "because they shattered me into understanding, and produced a volcanic eruption of music."

Recuperation also brought a lasting marriage with Maryanna, a blond, peach-skinned Aphrodite who hovers protectively while her husband gives interviews, partly so as to fill gaps in his memory. "Who are the Wellcome Foundation, Maryanna?" calls the composer from the garden to the kitchen, talking about his recently commissioned opera - a collaboration with the choreographer Wayne McGregor which will be about "the Sufi concept of extinction in the eternal feminine." I look blank, so he goes on: "The piece is called Layla, and I couldn't imagine how this could be done on stage because the central character has to be at one point unmanifest, at one point the Hindu goddess Parviti; at another she appears as the black Madonna of Christianity, then she's a buffalo cow-woman of the American Indians." It's good to know the Wellcome Foundation is lending its scientific stamp to this.

"In a sense what I'm writing now is not so different from Ultimos Ritos, the piece I wrote aged 28 which is now being done at St Paul's. It's the idea of annihilation in The Other - that there is only one Being. Wasn't it the Taos that said 'I don't know whether I'm a man dreaming I'm a butterfly, or a butterfly dreaming I'm a man'? Everything is one, does that make sense?"

Though he didn't understand it at 28, he says, he sees now that all religions - Christianity, Buddhism, Hinduism, Islam, whatever - say the same thing beneath different forms.

As if to prove a point, he is also working on a setting of the 99 different names for God in Islam. "I'm trying to do one name per day - well, almost - and it's wonderful because the music just comes to me immediately I see the Arabic word. For instance, today I did al Ghaffar which is 'the all-forgiving one'. Then there's Ar-Rahman and Ar-Rahim [he gargles the consonants in his throat convincingly]. The sound actually does help create the music."

I comment that Tavener must have set more languages than almost anyone in music, with scores in Arabic, Persian, Sanskrit, Latin, Greek, German, French, and even the language of the Sioux. Does it matter whether we hear or understand them? No, not really, he says. He went to hear the Marriage of Figaro the other night in Poole - sung in English, which he thought he'd hate. "But I loved it, and silently wept all the way through. Good music transcends words. Yet at the same time the Hindus say some words are holy in themselves. Ultimos Ritos has as its central movement just the name Jesu, repeated over and over. As a manifestation of God that name still has a certain sacredness."

So Sir John Tavener, like the character in the novel Life of Pi, will go on in his pluralistic way, in his case walking three hours a day in the Dorset hills and praying and composing as he goes. And no doubt his critics will continue to scoff. But the long and the short of it is that even works as unwieldy as The Veil of the Temple, which runs to 900 pages of score, is being requested in its full text from choirs as far flung as Amsterdam and New York, and the short version will provide Proms audiences with a taste of what they're missing.

Whatever critics' views on the music's compositional merits, it undeniably addresses a thirst for peaceful integration, for contemplation, for calm. In a world as culturally riven as today's, it's not outlandish to think that any inclusive gesture might help. And as Sir John is keen to point out in his quiet way, healing was the original purpose of music. *

'Ultimos Ritos': St Paul's Cathedral, London EC4 (City of London Festival box office: 0845 120 7502), Wednesday. 'Schuon Lieder' and 'Lachrymae': Cheltenham Festival (box office: 01242 227979), 16 & 17 July respectively. 'Atma Mass': Liverpool Anglican Cathedral, 18 July (free admission, to be performed during Eucharist). 'The Veil of the Temple': Royal Albert Hall, London SW7 (Proms box office: 020 7589 8212), 1 August