How did a blind Kansas kid become a composer with a global cult? Michael Church met the venerable Moondog

As formative experiences go, blinding yourself with dynamite - as a 16-year-old Kansas kid called Louis Hardin did in 1932 - might not seem auspicious. On the other hand, sitting in the lap of an Indian chief and beating out the rhythm for a sundance - as Hardin did when he was five - might instil interesting proclivities. Put these things together, and what do you get? In Hardin's case, a unique and magical fusion.

This is the man, better known by his nom de guerre Moondog, whom the journalist Walter Winchell famously found busking in a doorway; the musician whose importance Stravinsky vouched for in court, and with whom Charlie Parker would have collaborated, if he'd lived longer.

Smart minimalist composers Steve Reich and Philip Glass claim Moondog as the leader of their pack (a relationship he haughtily denies). The terminally smart designer Philippe Starck has dreamed up a Moondog building, consisting of a ziggurat with a rocket on top. Moondog's cult is global, but strongest in Germany, where he has lived for the past 20 years. For his appearance at the Queen Elizabeth hall on Saturday, as part of Elvis Costello's Meltdown Festival, it may be hard to get a ticket.

Paying him a visit, I get a shock: the tall, erect figure facing me in the doorway is none other than God the Father from William Blake's engravings. But exactly: the pure white shoulder-length hair; the flowing beard tapering down to the waist; the impression, given by the high forehead and concentrated frown, of a man in the deep trance of creation.

When he speaks, it's not in a voice of Thunder, but with the courteous tone of a Southern gentleman. Hardin may be 79, but he still moves with rangy elegance. Setting for our interview, he places himself still as a rock, as though listening to things which are more distant - and more interesting - than my somewhat predictable questions, to which he none the less eagerly replies.

It was from the Arapaho Indians, whom he encountered with his preacher father, that he absorbed the rhythms by which he measures everything he creates: "The running beat, and alongside it the walking beat, which is also the universal heartbeat."

He first encountered classical music at the school for the blind to which he was sent after his accident; there be learned to play the piano, violin and viola. But he owes his vocation to a book that his elder sister read to him. "It was called The First Violin - I'd love to read it again, but I can't find out who wrote it. Something in it spurred me to become a composer."

He then read a book on composition that convinced him he would never make it unless he mastered counterpoint, so he leapt this next hurdle with the aid of a braille tutor. He gravitated to New York, and became a compulsive eavesdropper on orchestral rehearsals in Carnegie hall. One day he happened to be sitting in the front when an unknown young conductor called Leonard Bernstein stood in for a national broadcast. "My handclap was the first applause he got, and it was heard all over the country."

He took to playing in doorways, and jotting down his musical thoughts in a braille notebook. Walter Winchell stopped to listen, and devoted a column to him. Charlie Parker heard him and suggested they do a record together. "But the next thing I heard, he was dead. So I wrote a piece, Bird's Lament."

Hardin developed a little hammer-struck harp which he dubbed an "oo", and a triangular drum which he named "trimba". "I thought I was being original in calling myself Moondog," be says wryly. "But I found the Alaskan Indians had used the word for a rainbow over the moon, and that it also appeared in a Norse saga."

This didn't stop him taking the pop-king Allan Freed to court, for commandeering his name and one of his records for the signature-tune to a radio show. Stravinsky was one of those who spoke up on Hardin's behalf; he won his case.

And in a superb gesture of defiance to the visible world, he invented a costume which he took to wearing everywhere - a Viking helmet, cape and spear. One day a record executive came by, and the rest is four decades of music history.

The tone-poems he recorded in 1956 - recently re-released - reflect his art in its purest form. While Hardin knocks out a gentle calypso beat at the piano, birds sing, and wind rustles through branches, as though a whole forest is rising and shaking itself. A Japanese woman sings a lullaby to her cooing child, while drums and metal percussion surround them with a caressing curtain of sound. Some tracks set Bach-like violin solos against Cuban drumming, others are dominated by street sounds. The aural beauties of a world that Hardin can no longer see are caught and blended with proprietary delight.

When I observe that his recent work resembles a Javanese gamelan ensemble, his brow furrows. "Gamelan is beautiful like all the birds in the forest singing together but it's not what I call composed. I've got similar effects by putting the sound of marimbas through a computer but mine is a true composition, a 16-part triple canon." A canon is in his view the highest form of music. "It's the most intellectually fascinating thing, yet the most musically uneducated person can respond to it."

Intellectually fascinating: in his eccentric way, Hardin is an exceptionally rigorous composer. He's contemptuous on improvisation: the only music that earns his full repect is that which has been put trough the analytical mangle time and again, to iron out every little "mistake".

For years, he says, he accepted Bach and Haydn as undisputed masters of counterpoint, because everybody told him so. "But then I began to say 'Hey, what's this?' - and the more I looked, the more mistakes I found. In the first fugue in The Well-Tempered Clavier, there's a mistake in every bar!" Does he think Bach knew this? "He probably didn't have time to check, with so many children, and having to produce a new cantata every week."

Mozart and Beethoven are also frequent offenders, with Handel the shining exception. "Stravinsky broke the rules, but here's a dynamic about him." So he's all right, then.

But Hardin also writes verse. This summer a German publisher is bringing out what he calls his 'millenniad'. "A thousand couplets about our abuse of nature, our contempt for primitive societies, and about a discovery I recently made which indicates the existence of what I call the Megamind."

When I ask for clarification he gives me a printed sheet entitled The Cosmicode which begins: "The Cosmicode emcompasses the Overtone Continuum, and it enshrines the Fact Inconvertible, to everybody's benefit."

He explains this, in a way that flies in the face of scientific fact (overtones on a plucked string go up in pitch, never down), but that makes a weird kind of mystical sense: "They say that every sound that ever was made is somewhere out there, floating around in the universe. Wherever there's a planet with an atmosphere they can be heard. Music is the one indestructible message."

Divine madness? If so, a very positive and productive one. When our colloquy is done, God the Father sallies forth into the streets with a hand placed trustingly on the shoulder of the woman he calls his "eyes". People stop and stare, and the traffic parts like the waters of the Red Sea.