The blond-haired, blue-eyed German first burst to fame in the early Fifties. His local Cologne newspaper acclaimed him the "year zero man", a pioneer of electronic music and constructor of bright new forms of composition. His fixation to be forever modern and original was just what a born-again civilisation needed after the horrors of Hitler and, worse still, Hindemith.
As his reputation grew through the Sixties, avant-garde allies became suspicious of the spiritual agenda that drove his increasingly grand and visionary works. Hymnen of 1967 was a breaking point: a two-hour electronic epic where 40 national anthems are slowly sieved into the sound of his own breathing - "The world is his ego," quipped a lapsed supporter.
When the Beatles, in reverence, placed him next to Freud on the cover of Sgt Pepper, Stockhausen's friends accused him of radical chic. John Lennon imitated the collage style of Hymnen in the White Album's "Revolution Number Nine" and then invited his hero to the famous concert on the roof. "I can't go," Stockhausen replied typically, "I have to work."
Admirers assert that the 250 pieces in his promethean output are like 250 unique journeys through space. You fly unconfined, though each composition is tightly controlled. Stockhausen has said that when you truly listen to music you become it. A notion like that miffs the Modernists. When he goes on to suggest that he has a mission to "bring celestial music to humans and human music to celestial beings", you can hear the seams popping on Pierre Boulez's buttoned-up shirt. Yet this is just the sort of "well weird" stuff that New Age blades love.
The point of no return was reached with Light (Licht). In 1977, Stockhausen, close to 50, discarded all lesser duties to create the world's longest opera. Calculating it would take 25 years to write, the whole would be ready by 2002, in time for his 75th birthday. The opera's seven vast sections, assigned to the days of the week, tell the story of Satan, Eve and the archangel Michael. Each possesses a serial melody that contains a genetic print of the opera's entire music.
So far he has made Thursday, Saturday, Monday and Tuesday. Now he is working on Friday and Wednesday. Already there is 20 hours of Light music, all of it, well, weird. Imagine the latest scene from Wednesday. The "Helicopter Quartet" was premiered at this summer's Holland Festival. It is scored for string quartet, four cameras and four helicopters. The musicians fly over the concert hall. Imagine, too, the insurance premium.
Weirder still is Stockhausen's new fame as techno's grandad. It is hard to conceive a composer more distant than he from the pulse-hammering, harmonically spartan world of technological dance music. Ambient artists can point to calm passages in Hymnen or Momente as forerunners to their aural landscapes of lush, unhurried harmonies. But Stockhausen will swiftly remind them that he has evolved a sophisticated serial language that can embrace violence and serenity from one second to the next.
For this reason my radio producer Lizzie Jackson and I decided to confront him with the musical evidence. What did he make of it all? We chose four ambient or techno artists who had cited Stockhausen's name or for whom the rock press had imputed an influence and asked them to send a 15- minute DAT tape of their music. Four times 15: "Just an hour of your time, Professor Stockhausen," we wrote, precisely.
We met a man of shining self-assurance. He is tall and hefty and dressed entirely in white. He talked to us generously about technology, universal unity, and techniques of composing, but he couldn't wait to give vent to the tapes. He balked at their "permanent repetitive language... like someone stuttering all the time".
In doing so, he hit on the fundamental issue of art music in this era. It's not tonality, it's repetition. He has lived by a tradition that designed systems to avoid repetition. Yet it may well be that a repeat- freak such as Sibelius will prove more influential to this century than Schoenberg.
Stockhausen was also nagged by the thought that their music was a background to something else, whether dancing or tripping. "Music is the product of the highest human intelligence. As soon as it becomes a means for ambience, of environment, then music becomes a whore."
Oh dear. Still, he had listened to the tapes and made notes. He began with ambient star the Aphex Twin, aka Richard James. His music sounds like a school kid emulating Philip Glass (with whom he has in fact collaborated), with its cyclic harmonies backed by a drum machine. Stockhausen glances at his notes through half-moon specs, like a doctor checking a prescription.
"Mr Richard James. I think it would be very helpful if he listens to my work Song of the Youth (Gesang der Junglinger, 1955), which is electronic music and a young boy's voice singing, then he would stop with all these post-African repetitions and would look for changing tempi and changing rhythms."
Second, Plastikman. A border Canadian, Richie Hawtin builds prolonged rhythmic sequences from simple pulses in his austere techno dance tracks. "He starts with hundreds of repetitions of one small section of an African rhythm, tu-du-dum. It would be helpful if he listened to Cycle for percussionists (Zyklus, 1959), which is only a 15-minute piece. He will get a taste for interesting, non-metric and non-periodic rhythms."
Third, Scanner. The infamous Robin Rimbaud operates a scanning device to record banal conversations on mobile phones, then places behind them chaste, inert harmonies to invoke an unsettling atmosphere. Stockhausen warmed to him. "He is searching in a realm of sound that is not usually used for music. But I think he should transform more what he finds; he leaves too much in a raw state. He has a good sense for atmosphere, but he is too repetitive again. So let him listen to Hymnen. There are found objects a lot, like he finds with his scanner, but he should learn the art of transformation, so that what you find sounds completely new. As I sometimes say: like an apple on the moon."
Finally, 18-year-old Londoner Daniel Pemberton (included partly because youngsters are Radio 3's target audience for this series). Pemberton's debut CD is titled Bedroom, because that's where it was made. Worked out on homespun electronics, his moody rhapsodies sound like ambient film scores. Stockhausen is aware of Pemberton's youth and adopts a mock-severe tone.
"Mr Pemberton likes the loop effect as in musique concrete, where I worked in 1952. So I think he should give up this loop, it is too old-fashioned. His harmony sounds to my ears like ice-cream harmony. Look for a harmony that sounds like Pemberton and not like anything else! He should listen to Kontakte (1958), which has among my works the largest scale of unusual and demanding harmonic relationships."
He puts his glasses away, looks down at me with his searing eyes, and bestows a valediction. "They should learn from works that have already gone through a lot of temptations and have refused to give in to these stylistic or these fashionable temptations." He leaves to get on with his work. The encounter was, as they say, well weird.
n 'The Technocrats' begins today at 5pm on Radio 3 and runs every day until FridayReuse content