Olivier Messiaen didn't bother to break the rules of musical composition; he simply made up his own. Stacking chords into pillars of shimmering sound, disposing with conventional narrative structures, juxtaposing complex rhythmic patterns with melodies of stunning simplicity, he created what was - what still, in many ways, is - a new kind of sound. However, having ignored the gospel which had prevailed in music since the time of Bach, this most eclectic of 20th-century composers wasn't about to subscribe to the infant musical orthodoxies of serialism and atonality, either. Instead he sought inspiration in areas which, for most of his lifetime, were very unfashionable indeed: religion and nature. By the time he died in 1992 Messiaen was recognised as an eminence grise by the European establishment - and regarded by historians as a kind of musical cul de sac. But there are signs that the 21st century may take Messiaen to its heart. He was the very essence of a new age composer, and with its heady cocktail of nature-worship, birdsong and mystical Catholicism, with a dash of eastern mysticism stirred into the mix, his music seems guaranteed to appeal to audiences at home with floating candles and feng shui. Certainly it is being recorded with increasing frequency, and live performances are no longer as rare as they once were. Irish concertgoers will have a chance to experience Messiaen's music for themselves this weekend during a four-day festival organised by the Royal Irish Academy of Music and the National Gallery of Ireland. The programme of recitals and master classes will culminate in a performance of Messiaen's Quartet for the End of Time on the 60th anniversary of its first performance. Messiaen and three colleagues gave the world premiere to an audience of 5,000 fellow prisoners in a German prisoner-of-war camp, Stalag VII, on January 15th, 1941; it was so cold that the keys on the decrepit upright piano played by the composer threatened to freeze solid. Conditions at the National Gallery on Monday next, when the quartet will be played by John Finucane (clarinet), Michael D'Arcy (violin), Aisling Drury Byrne (cello) and Therese Fahy (piano), will undoubtedly be more luxurious, but the music's emotional impact has not lessened in the interim. If anything, time - and our appalled retrospective understanding of the significance of 20thcentury stalags - has increased its potency. No one should run away with the idea that Messiaen makes for easy listening. As the critic Bernard Holland wrote in the New York Times last February following a performance of the Turangalila symphony at Carnegie Hall, "Most Western music is about time. Each piece is its own clock, with hands that move from a starting point to a conclusion. Messiaen's music is about space. Listening to it is like standing in the middle of a forest or even a city street. The ear behaves as the eye usually does, taking in a scene all at once, then isolating its details . . . " The 80-minute Turangalila, however, is a mammoth work, famous for emptying concert halls - a disgruntled critic wrote after one performance that the audience must have mistaken Messiaen for Handel's Messiah, given the rate at which people were slinking out in the pauses between its 10 movements, while another complained that the work's descending harmonic sequences sounded like "fat chords falling down stairs".

Dublin will hear the kinder, gentler side of Messiaen. In a lunchtime recital at the National Gallery on Sunday (1.05 p.m.), Hugh Tinney will pair Messiaen piano preludes and studies with a Mozart sonata, while at the RIAM on Monday the French pianist Jean Dube, fresh from winning second prize at last month's "Concours Olivier Messiaen", will place Messiaen alongside contemporary composers Wolfgang Rihm and Gyorgy Ligeti. Saturday's lunchtime concert at the gallery will see Dearbhla Collins and Therese Fahy perform Sept Visions de l'Amen on two pianos, while at 8 p.m. in Christ Church Cathedral, the Lebanese organist Naji Hakim will place his former organ teacher in context as a significant composer for that instrument, combining extracts from La Nativite du Seigneur with pieces and improvisations of his own, including Le Tombeau d'Olivier Messiaen. On Sunday night at the RIAM, a trio composed of Eyal Kless (violin), William Dowdall (flute) and Dearbhla Brosnan (piano) offers a programme of Messiaen and Bartok.

On Friday evening the festival kicks off with a recital at the National Gallery by the pianist Paul Crossley, who studied with Messiaen's wife Yvonne Loriod in Paris in the 1960s - though, in effect, this meant studying with "le maitre" as well. "The lessons might go on for hours," Crossley recalls. "At about four o'clock Messiaen would usually be back from teaching his class at the conservatoire, so he would join in too. Neither of them ever seemed to worry about time. It was more like being an adopted son." Crossley, who will also give a master class to students at the RIAM on Saturday, remembers Messiaen as totally uninterested in such things as status and standard of living. "The apartment was in a part of Paris that - well, it wasn't exactly a slum, but the building had once been a hotel, and when you wanted to go to the lavatory you had to get the key and go along the corridor to a shared bathroom." And this at a time when Messiaen was pretty well off - but the composer's lack of interest in outward appearances was, according to Crossley, absolutely typical.

"He regarded modern society with complete horror - he thought that it lacked any kind of spiritual dimension whatsoever. And though he loved people to be enthusiastic about his music, and would sit for hours in green rooms while people brought him scores to be autographed - he wouldn't sign his name, he'd write little messages - he would have hated to be a celebrity. That would have been anathema to him, that kind of thing."

As for Messiaen's celebrated Catholicism, it might be more accurate to write the word with a small "c". "All his music was dedicated to the glory of God," says Crossley, "but he had far too many pupils from Asia to be insistent that you had to be a Christian to appreciate it." He points out that in Messiaen's oeuvre, despite the many religious titles, you won't find settings of the big Catholic setpieces. "There's no Mass, no Stabat Mater. Also, he was genuinely interested in Hindu and other eastern cultures. And the Catholic authorities in the church where he played the organ every Sunday, I mean, their eyebrows turned up on lots of occasions at the kind of music he was actually doing for the services. "But he was a very literal Catholic in some ways. In the score of his opera St Francis of Assisi there's an angel who comes down and speaks to St Francis, and he wanted her to be dressed in white robes with great plastic wings on her back. And when he saw a production in a more modernistic style, he was terribly offended by it; so although he had this very broad outlook, and almost a world view of religion, he really liked the traditional iconography. There was this contrast when you met him - an immensely challenging and revolutionary figure as a composer, and somebody with a very plain, down-to-earth, lower-middle-class acceptance of the world."

Crossley's programme will team Debussy preludes, Takemitsu, and his own composition A Vision of Takemitsu, with excerpts from Messiaen's contemplative Vingt Regards sur L'EnfantJesus, Des Canyons aux Etoiles, which evokes the numinous grandeur of Bryce Canyon, Utah - and the famous, or infamous, Catalogue d'Oiseaux. What are we to make of a composer who genuinely believed that it was possible to transcribe birdsong into music? Or did he? "Oh, absolutely. He was very serious about it. And you can recognise them, by the way. I remember the first time I went to Australia, and I was sitting outside a studio while the orchestra were rehearsing and heard quite distinctly the bird that opens Oiseaux Exotiques, which is an Australian bird. On the other hand, to hear a garden warbler twittering away and then to hear Messiaen's piece called that - well, there's no comparison. But he liked to think there was - and he was terribly disappointed because ornithologists didn't recognise them either!"

Crossley insists that Messiaen's use of birdsong was more than just a decorative motif. "During the 1950s he had come to a kind of dead end in his work, and he was very depressed indeed. All his pupils were going into what we now think of as plinkyplonk modern music - and though he tried his hand at it himself, and wrote very good serial pieces which people still play, he couldn't stand them. He felt that serial music wasn't expressive enough. To cheer him up, an ornithologist friend offered to take him out at three o'clock in the morning and point out all the various birdsongs, something he had been interested in in a general sort of way. And it really was a new lease of life, a real piece of inspiration for him. So one mustn't laugh at the birdsongs because there wouldn't be any late Messiaen music if it hadn't been for the birds."

For information and to book for the Oliver Messiaen Festival, phone 01-6764412