From the earliest work he currently acknowledges, Things that Gain by being Painted (1977), Gerald Barry's music has been notable not only for its individuality, unpredictability and uncategorisability, but also its wit. These are characteristics the work shares with its creator. When I met him at his house in Arbour Hill, Dublin recently, he opened the interview, out of the blue, with an offering of anagrams: "Berlioz puree" (for the French composer and conductor Pierre Boulez), "he fry brain enough" (for the intellectually demanding British composer Brian Ferneyhough) and "large dry bra" and "dry lager bar" (for himself).

We talk about his new CD, a collection of instrumental and chamber music ranging over 20 years, on the Black Box label. "It's quite a surprise," he says, "in the sense of the amount of silence in the pieces, the way the pieces breathe. There's a lot more space in the music, which is in a way quite unlike a lot of the more recent work. Also, in a way, by going back to these early pieces I have found a way to proceed in the future, taking my cue from these pieces, even though I had been thinking this way anyway."

I ask about the silence, so long you can hardly believe it's intentional, at the beginning of his 1979 piece for two pianos (the work's title is graphic, a circle with a tilted line through it). He explains it as an almost visual gesture, an isolation of something ordinary (just two notes) which can become extraordinary through the setting you place it in. This concern, as important to him now as 20 years ago, brings musings on the inevitability of some of life's trajectories - "I now realise more and more that all of the things that one becomes later in life, no matter where you go in the world, whether you study in Vienna or Cologne or wherever, all of the things are already there before you leave" - and also leads him to talk about some of his most fundamental concerns.

He likens the piece's opening gesture to looking at a cup on a table, "and looking at it very intently, so that the intense looking raises it in some way. It's as if it were magnified. It's as if, by looking at it for a long time, you will somehow plumb its secret, its - I hate to say it - its `thereness' or whatever. I now realise that I've always wanted to touch things, whether it be in music or actually touching, ever since the earliest times I could remember."

He recalls a childhood obsession with a wall on the way to school which he felt compelled to touch in certain places every day. He goes so far as to describe it as "throbbing, waiting for me to touch it every morning". In a gallery, he needs to look at a painting for a very long time, in order to enter into it, to be absolutely at one with it, so that he and the painting are indistinguishable. "Once I had looked at the painting and grasped its secret I would then leave the gallery with my eyes downcast, lest I see something disappointing . . . or some unattractive person wearing a duffle coat.

"You want to leave the building with the secret you have grasped in your head. If you do see something disappointing - it's usually a person - you have to go back, then, to the painting and begin all over again to try and recover the painting.

"With a moment like the opening of the two piano piece, you are trying to bring into being a moment that will always be that, no matter who plays it, that will have always the feeling you are hearing it for the first time, that will always have that freshness. That is the aim of writing music, to grasp the intangible and make it somehow concrete in a mysterious way, so that it will always have that sense of . . . of coming into the room for the first time. A messenger will always be coming to you with fresh news."

He recalls a visit to a room in the Wallraf-Richartz Museum in Cologne, with large paintings on three walls by Rothko, Barnett Newman, and Frank Stella. "There were people in the room as well, being cheerful. I hate that. I hate this kind of bonhomie in public places like galleries. It somehow gets in the way of the work. So I tried to look as glaring as possible to crush their mood and I finally forced them to leave. Then, once they left, I quickly went around each painting and laid my cheek on the canvas, which, of course, is a terrible thing to do. Then, I left the building immediately, looking at the floor all the way out, feeling somehow that I had touched a part of the Grail. "That is the quality, really, that I aim for in music. It's like touching with intent. It's not only a matter of, say, with a visual object, like a piece of sculpture, where you can touch it, but also, touching in terms of sound, viewing the musical material as if it were an object and respecting it completely. And an intense desire not to betray it. And almost, a sculptural desire that, whenever you hear it, it will always have a quality that is unfathomable. That's the idea, anyway. Whether one reaches it or not is another matter."

It's easy to see a painting as a visual moment, not at all as easy to see how a piece of music, revealing itself through time, can be regarded in the same way. "I don't make any distinction between the two. There is no difference for me between hearing a Beethoven quartet and standing in front of, say, the Monet painting of snow in the Hugh Lane Gallery"

For Barry, though, it's the Beethoven which is the more interesting. "At the moment, for me, there is no artist I know of who equals Beethoven in any discipline, even someone like Proust, who is extraordinary, or Cezanne. I just feel that. Maybe it's the nature of Beethoven's music. It's utterly unpredictable. That is not to say you won't find when you return to Proust and you return to Cezanne that they aren't also unpredictable. But there's something about the extraordinary range of Beethoven that is satisfying, endlessly satisfying, endlessly rewarding, and surprising and shocking. And all of those things could be said about Cezanne and Proust as well. But you can say them more so about Beethoven."

Talking to Barry, it's clear the demands he makes of himself are at least as high as those he notoriously makes of performers. "I find the writing of music mostly incredibly difficult." He quotes Beckett: "The expression that there is nothing to express, nothing with which to express, no power to express, no desire to express, together with the obligation to express." The age we live in, he feels, is a bleak time. "I think that most work in all disciplines, artistic work, is unnecessary. I'm not saying by that that I think my work is necessary. The world is clogged with unnecessary artistic activity. Whether I am deluding myself or not, my aim would certainly be . . . if possible, if I could be aware of it, not to add to that."

He's currently hoping to create necessary additions with a second string quartet, to be premiered by the RTE Vanbrugh Quartet at the West Cork Chamber Music Festival next year, and a setting of Nietzsche, The Eternal Recurrence, a millennium commission from the BBC for the Ulster Orchestra.

Gerald Barry's music is recorded on the Black Box, NMC, Largo and Marco Polo labels. He will be a featured composer, with Kevin Volans, at the Sligo Contemporary Music Festival, which runs from Friday, November 27th, to Sunday, November 29th. His first String Quartet and 2nd Piano Quartet will be performed on November 16th-17th at the International Festival of Contemporary Music in Moscow and the Bavarian Radio Symphony Orchestra with Stephen Richardson (bass) gives the German premiere of The Conquest Of Ireland at the Musica Viva Festival in Munich on November 20th