The man who put opera on the front page

"The worst thing for me," he confides, "is dealing with what I call the OW the Outside World. When you have 30 to 40 pieces that are getting played all the time, having to babysit them that gets to be a problem." It is not a problem shared by most composers, who are lucky to get one piece performed every 30 to 40 months, but then Adams has always been in a class of his own. At Harvard in the 1960s, he shunned academic atonality for John Cage-led minimalism, tiny tunes minutely altered in endless repetition. Then he rejected that crab-like process in favour of big themes and hot political topics that got him on the nightly news. Unintentionally, he insists: all he wants to do is compose.

"I get up at the same time and do the same thing every day, nine to five," he says, trying to explain his working processes. "Once I have established what I call 'the genetic code' of a piece, I become like a gardener. It's a matter of being judgmental about cropping this and watering that. The piece tends to grow by itself. Don't ask me where it comes from." Dull as he pretends to be he is wearing a worn tweed jacket and talks in a drone Adams has not been out of the headlines since 1987, when he became the first composer to put current affairs on the opera stage with Nixon in China, which showed two ailing leaders trying to reorder the universe. It raised issues of veracity and irreverence Nixon was still alive at the time, and Kissinger came out pretty badly and in the process shot opera out of its eternal fixations with what comes first, words or music, and who's the next big tenor. Opera, after Adams, began to grow up and read the papers.

Four years later, The Death of Klinghoffer, dramatising an Arab hijack of a cruise liner, provoked a storm of protest for supposedly belittling the murder of a disabled Jewish passenger, whose wheelchair ends up dumped in the Med. He maintains the opera was misunderstood.

"Politically, it became fashionable to say that it was a work that romanticised terrorism. But look how it ends. We are left with this 70-year-old woman who has lost her husband for reasons she doesn't understand.

We read every day about 30 people killed in Baghdad and it's meaningless. What Klinghoffer does is take it personally." Although he continues to address political events in other forms notably in a 9/11 choral ode, On the Transmigration of Souls Adams dodged opera for a decade until San Francisco came looking for a Faust story and suggested the idea for Doctor Atomic (which receives its UK premiere at the Proms), a study of the hearts and minds of the men and women involved in the first A-test of 15 July 1945, three weeks before Hiroshima. "At that point I didn't think I'd write another opera but I saw Doctor Atomic as a heroic story with a tragic ending. All of these young scientists who thought they were saving the world from Hitler were actually creating the means of destroying it." Adams was inevitably attacked for Left-wing, liberal, even anti-American bias. He retorts that J Robert Oppenheimer, director of the Manhattan Project and hero of the opera, had his life wrecked after the war by Right-wing McCarthyites. "The issues are too important be reduced to Left and Right," Adams argues.

"We need to know the facts and we need the human dimension." His libretto consists of lines selected from the scientists' memoirs and declassified government documents, mingled with some of their favourite poems. The first act ends with Oppenheimer singing John Donne's Holy Sonnet, Batter My Heart. In the bedroom with his troubled wife, he quotes Baudelaire.

Adams's latest opera, A Flowering Tree (playing at the Barbican), is a South Indian parable of love and loss. Although unrelated to current events, it nonetheless exposes ways in which ordinary lives and ecologies are disrupted by the mighty. An agenda is evident and Peter Sellars, who directs all of Adams's operas, has claimed credit for it.

Not quite, says the composer. "Peter came up to me with the idea of Nixon in China. Klinghoffer was his as well. But I suggested all the others.

Peter is a symbiotic artist: he absolutely has to work with somebody else. I love working with him but I also love working alone. He has a great capacity to fertilise someone else. I very often say about Peter, he's the sperm and I'm the egg."

Adams says it was his mother who put him on stage. "My mother was an untrained actress in a small town, East Concord, New Hampshire. I appeared with her as a little boy in South Pacific, singing Dites- Moi Pourquoi.

"I had the fantasy of becoming a composer when I was nine years old. It was the 200th anniversary of Mozart's birth and our thirdgrade teacher read us a child's biography of the great composer. I took a piece of paper, a pencil and a ruler and went out into a field behind our house and tried to write something. To my shock and dismay, I realised I didn't have the tools. So I went back and told my parents and they found a person to teach me theory. I wrote my first piece when I was 10, an orchestra work when I was 13. It was actually played." His father "a travelling salesman of nuts and bolts" taught him to play clarinet and listen to Benny Goodman. The window of the town record store introduced him to Sibelius.

"There were snowy landscapes on the covers that resembled New England," he reminisces..

At Harvard he was spotted by Leonard Bernstein and offered a place in his summer entourage. He declined, preferring to work alone. He moved to California in 1971, married the photographer Deborah O'Grady (they have two grown-up children), and apart from a short stint teaching college has lived entirely from daily composition, nine to five.

His friends are as likely to be scientists as artists and he agonises over the disparity of the concerns of his social enclave and those of mass society. "America has an anti-intellectual bent," he winces. "Bill Clinton, this intensely brilliant Rhodes scholar, won the election by being a hillbilly, playing blues sax and eating pork at barbecues. But there is also an American gift that Bernstein had, and the great poets had and that is to be part of this society and still have a transcendental vision of it." That is the mantle that Adams has now inherited. He is the artist to whom America turns to make sense of its confusions. Doctor Atomic will be staged at the Met next year by the Channel 4 director, Penny Woolcock, who gave Klinghoffer its widest reach on television.

The issues that Adams cares about are getting aired. Now he's listening again to Sibelius, the symphonic purist of his teens. What has he learned along the way, I wonder? "At the age of 60," he says wryly, "I am here to report that music is about feeling as much as it is about meaning." A Flowering Tree is performed at the Barbican Friday 10 and Sunday 12 August (0845 120 7555). Doctor Atomic premieres at Prom 50 on 21 August (020 7589 8212).