On the banks of the River Thames, in the lee of Canary Wharf's towers, Trinity Buoy Wharf is a mix of wasteland and empty buildings rubbing up against ship containers that have been converted into living spaces and a thriving subculture of artists' studios. There's even an American-style diner. It is the home of London's only lighthouse, built in 1864 to carry out experiments in light. Now it is the home for an experience in sound.
On Jan 1, 2000, as the clock ticked into the new millennium, Jem Finer, the banjo player with the shock 'n' roll group The Pogues, pressed a computer button and launched a piece of music he wrote to last 1,000 years. "For a long while I had been pondering how to make a piece of work that engaged with time," he says in his memorably cluttered office near the lighthouse, just across the river from another millennium project, the Dome.
"What sparked the eureka moment was thinking about the millennium. What is 1,000 years? Ultimately, it is a very arbitrary figure based on the coincidence of having 10 digits on the end of our hands and certain agreements about when calendars start and stop. It occurred to me that to make sense of it to myself I'd like to make 1,000 years of something. "It didn't have to be a piece of music, but then it popped into my head when I was playing around with an old-fashioned laptop letting routes of music of different length run in and out of phase. I thought, 'Hang on, if I calculate this right I could make a piece of music which would last precisely 1,000 years.' "
The result - appropriately called Longplayer - was created with a computer, an array of Tibetan singing bowls and his own powers of invention and imagination. Finer composed six short pieces of music that are played simultaneously. The computer chooses and combines these sections in such a way that no combination is repeated until exactly 1,000 years has passed. Longplayer can be heard in the lighthouse and five other listening posts around the world, including one in the new Bibliotheca Alexandrina in Egypt, as well as at www.longplayer.org. This month, Finer is holding a live performance of the work - 1,000 minutes of it - at London's Roundhouse.
He has lined up 26 musicians, including the fellow Pogue Darryl Hunt, to play the singing bowls - used in eastern rituals for meditation and religion - which will be set out on tables in six concentric circles. As the music plays, a Long Conversation will take place involving a relay of talks by such celebrity writers and academics as Marcus du Sautoy, Susie Orbach and Jeanette Winterson. "It is all well and good using a computer to create the piece, but if you are trying to make something last for a long time it is pretty stupid to tie it to one technology because you don't know what's going to happen," says Finer.
As he unpacks a bundle of short-sleeved cotton shirts and matching trousers that he had specially made in India for the performers, because "it is important what you wear in a performance", he explains: "As soon as you get beyond one generation of technology, you really start not knowing. I had to be very careful that the computer wasn't doing anything other than the emulation of simple physical actions because if the computer started doing all sorts of spectral manipulations, you'd be stuck.
"Longplayer is not a piece of computer music because it can be reduced back to an original score, a set of instructions that are predictable. The computer is a cheap, efficient, convenient way to start off the music's life, but the point is that there are a finite number of combinations." Does he ever contemplate the idea that the computer will take over, such as the wayward Hal in the film 2001: A Space Odyssey, and make its own music?
"The computer's not bright enough to do that yet," he insists. "One day, maybe. In a sense, Longplayer is already a Hal because although I've made the system and I know how it began and how it ends, I don't know what combinations will occur in between. That's unpredictable. There could be whole sections that are absolutely horrendous, maybe a section lasting 100 years which is totally unlistenable because of the combinations.
"It will have its ebbs and flows, its climaxes and moments of relative peace and tranquillity, day by day, week by week, month by month. It will always be familiar, like the sky - sometimes incredibly surprising in a beautiful way or a boring way. I could work out how many combinations there are - if you sit there long enough." He taps at his calculator. "It comes to 15,000,000,000. Or something. What I'm doing with the show is returning something which has been conceived using digital technology to something that is physical and tactile.
"If I had thought it out properly in the beginning, I could have sorted it out without a computer, though I would have needed a lot of people on standby for 1,000 years and the music written out in hundreds of thousands of books." Easier to assemble and certainly more reliable are his singing bowls. "My friend Darryl Hunt suggested I use them and it was a revelation. Once I was pointed towards them, I couldn't understand why I'd missed them."
The floor of his space is covered with the bowls, fighting for room with two pianos, a large desk, music consoles and clutter including a guitar, shelves of cassettes and CDs, and a drum high on a ledge. He pings away to prove the bowls' versatility and variety, running a stick around the lips of one to make a high-pitched sound like a finger on a glass. A rap or a tap from a little leather-wrapped mallet produces a range of sharp notes, interjections and warm bell tones.
"These instruments are so robust they are they are not going to go out of tune," he says. "What is so pleasing is that when you play a number of them together you don't necessarily hear them separately. Their sounds combine symphonically to create new sounds. "I came to the idea of using them very slowly. One of the reasons was that in composing Longplayer, it had to be translatable into other forms and easily reproducible. If I had used the strings of a piano, they would have gone out of tune. They would have rusted and broken. And there was the problem of keeping the music from being culturally out of sync by using very contemporary forms and idioms which would soon sound out of date. These bowls provided a great answer because they are already old and the sounds don't have a date attached to them - not like a drum sound that you would hear and say: 'That's very Eighties.'"
Longplayer Live will be the first time the work will be played by people, without any electrical or mechanical aid. "Once it had started to play, it raised all sorts of cultural ideas about music and the physics of sound. It became a huge, all-encompassing project and, of course, it wasn't a case of 'OK that's the end of it', it was more a sense that it was the beginning - how do we keep it going and how move it on in these different forms. In that sense by going live it has taken 10 years to realise the first stumbling step into a possible different route for Longplayer to take."
Meanwhile, a steady stream of pilgrims make their way by road, rail and river every weekend to the lighthouse to listen to the steady drone, hums and harmonies, discordant, jangling interruptions and moments of silence that characterise Longplayer - a mix of extra-terrestrial warblings and eastern mysticism with a dash of whale music and a touch of the whimsical sounds of Enya. The noise grows louder and more intense as you walk up the stairs to the lighthouse gallery with its views along the Thames.
"It is still very young people who come along and look at the visitors' book, rather in the way people used to carve their names in a bus shelter," says Finer. "There are regulars and there is always an element of referring back and people saying: 'I heard something like this before in 2003 or 2007'. It's already accruing a history and a meaning for people, which seems to be about their feeling of looking forward. Some people just stumble about, some people think it's mad, others are totally fascinated and get taken in by it."
A small screen clocks off the hours, minutes and seconds, while a wavy line reflects the changes in notes. It is impossible not to stop and listen and be aware that someone else could well be doing the same thing in 991 years' time. Will the Dome still be there, Canary Wharf, the lighthouse itself? Look back 1,000 years and history tells us that King Canute was preparing to conquer England, the Norwegian Leif Eriksson had discovered America and the first statues were being erected on Easter Island. Maybe the dirty old town of London will have fallen into ruin by 3,000, but perhaps Longplayer will still be making music and some chronicler will be peering at the 31st-century equivalent of Wikipedia to discover just who was Jem Finer. The Pogue might still be in vogue.
Longplayer Live is at the Roundhouse, London, on September 12. www.roundhouse.org.uk.