Olivier Messiaen, whose centenary is celebrated this year, believed birds were the best musicians and went to great lengths to steal their tunes for his work, pianist Thérèse Fahy tells Arminta Wallace

AS I SIT at the computer typing these words, a bird is singing merrily outside the window - a delightful sound on a dreary, drippy autumn day. But is it, strictly speaking, music? That's not the only question raised by the flutings of our feathered friends. If birds sing primarily to find mates or to mark out territory, then why does one bird suddenly go nuts in October, when the mating season is well and truly over? Come to think of it, why do some birds engage in elaborate curlicues, trills and improvisations at any time of year, when a short, sharp shriek would probably do the evolutionary trick?

There are those who believe that birds, like humans, make music for the sheer joy of it. Jazz saxophonist David Rothenberg regularly takes his instruments into aviaries and "jams" with birds. This, he hopes, will help him figure out whether they "hear" music as we do; which may in turn help find an answer to the question of whether - and how - we can ever really communicate with other species. His investigations cross the boundaries between art, science and philosophy, prompting us - as he insists in his book, Why Birds Sing -"to reconsider what music is and where it came from".

Rothenberg's avian endeavour will strike many people as quite mad. Without doubt, however, it would be music to the ears of the French composer, Olivier Messiaen, the centenary of whose birth is being celebrated this year. Messiaen regarded birds as the best musicians, and reproduced a great deal of birdsong in his own music. At first he used it in quite an abstract way - birdlike themes appear, for example, in his Quartet for the End of Time, written during his stay as a prisoner in a German internment camp during the second World War.

"The birds," he wrote in his notes for the piece, "are the opposite of time. They represent our longing for light, for stars, for rainbows, and for jubilant song."

In his later works Messiaen became interested not just in the melodies of birdsong but in its rhythms and tonal qualities, which he sought to recreate in an ever more precise musical manner. In his search for ornithological exactitude he went as far as Australia, where the Brisbane birder, Syd Curtis, described driving the composer into pitch darkness, in the middle of nowhere, in search of an elusive warbler known as the Albert's lyrebird.

"I held a flashlight while Messiaen wrote busily on manuscript paper," is how Curtis later remembered this surreal outing. "Madame Messiaen kept him supplied with sharp pencils. After 20 minutes or so, no new bird sounds were being made, and he decided he'd got them all down. So he turns back to the beginning and goes through his notation, whistling or singing with such accuracy that I had no trouble in identifying the species for him."

Madame Messiaen was the concert pianist, Yvonne Loriod, for whom many of Messiaen's pieces were written, including the 1953 orchestral work, Réveil des Oiseaux.

"It's horrendously difficult, but also very beautiful," says pianist Thérèse Fahy, who will perform the piece with the National Symphony Orchestra at the National Concert Hall at the end of this month in what she is "99 per cent certain" is its Irish premiere. The music evokes the magic of the dawn-to-dusk world in the Jura Mountains, using the bird sounds you might hear from midnight through to noon the next day. Messiaen's instructions to the soloist are, to put it mildly, unusual.

"At the beginning of the piece he says to the pianist, 'You must go walking in the woods'," says Fahy. "Not something you'd normally get on a musical score. As for the score itself, it's very visual and highly descriptive. There's one place where he says the starlings should be 'like castanets'. You can just see them strutting around like Spanish dancers: dah-RRAM, dah-RRAM, dah-RRAM. There are 38 birds altogether, which are listed at the beginning - look - as if they were a cast of characters."

The names are also written on the score as each bird enters the fray. Fahy flicks through the pages, spotting the various species: the little owl, the whitethroat, the thrush, the woodlark.

THE WAY IN which Messiaen weaves birdsong into a piece for orchestra and soloist is remarkable. "Every tiny little thing that you hear is part of a bird call, even the tiniest pizzicato in the bass," says Fahy, who confesses that birdwatching has never really been her bag. "My brother Kieran has always been interested in it, though. I rang him up this morning and said: 'Nightingales - have we got any in Ireland?' And off the top of his head, he goes: 'Well, there have only been 15 sightings . . .' He lent me four CDs of actual bird songs, so I can check out the ones I don't know so well." She stops and laughs. "I've got really nerdy about this, haven't I?"

The more she delves into the music, however, the more Fahy says she appreciates the breadth and depth of Messiaen's expertise. "The characters of the birds are amazing. The robin is cheeky and bold. The blackbird is quite military. For the carrion crow, your two hands are down in the bass and you get this kind of . . ." She executes a rapid rumble on the surface of the table of the cafe at the National Gallery of Ireland. "What I find interesting are the silences as well. There are two big silences in this piece, one at dawn and the other at midday. And birds really do that. I happened to be out at the back of my house yesterday, and they do stop. You'll hear 'Whooooooo-UH', and then there's a stop. And then you'll hear another guy in another tree. It's as if they're saying to each other, 'okay, now it's your turn'. The stops are hilarious. And you can see the heads moving. Listening."

Messiaen's music places considerable technical demands on the pianist.

"Birds sing so fast," Fahy says. "It's all 'diddle, liddle, liddle, lum', you know? At the speed of light. There are an awful lot of repeated notes. Then you've got these patterns where notes are repeated upside down and inside out. So you have, like, eight different versions of the same notes in different arrangements. It's kind of dizzying, learning it, because the articulation is difficult." She twiddles her fingers. "Birdie stuff."

Having already played movements from Messiaen's massive solo piano work, Vingt Regards sur l'Enfant-Jésus, at the Hugh Lane Gallery this year, and curated a festival for the 60th anniversary of the Quartet for the End of Time,is Fahy - who teaches piano at the Royal Irish Academy of Music around the corner in Westland Row - becoming something of a Messiaen specialist? She makes a face.

"I hate the word 'specialist'," she says. "I just seem to have found myself playing a lot of Messiaen, that's all. But then, I've always been attracted to French piano music."

She studied in Paris, and once performed all of Debussy's piano repertoire at the Hugh Lane gallery. She also once met Messiaen in person. "In 1991 he came to the academy to get a fellowship," she says. "Myself and Mary Collins were doing a two-piano piece of his, called Visions de l'Amen, and we couldn't believe it - he came to Dublin a week before our concert. We missed him by a week. But I was able to talk to him about the piece, and he drew me a diagram of how the two pianos should be placed on stage. He died the following year."

MESSIAEN WASN'T THE only composer to be fascinated by the musical possibilities of birdsong. His compatriots, Rameau, Ravel and Dutilleux, also wrote pieces based on bird calls, which will be performed as part of a concert called Birdsong Becomes Musicat the Aula Maxima, NUI Galway, on Wednesday, December 3rd. Which brings us back to our opening question about the relationship between birdsong and music. Are we closer to an answer? Probably not. But Fahy's close encounters with Messiaen's music have convinced her that his interest in birds amounts to more than just an ornithological oddity of music history, or some kind of gimmicky "tunes for twitchers" hobby.

"He was a very spiritual man and a devout Catholic," she says. "Messiaen saw birdsong as part of the whole spectrum of nature praising God." And that's a question for another day.

Thérèse Fahy plays Messiaen's Reveil de Oiseaux with the National Symphony Orchestra, conducted by Gerhard Markson, at the National Concert Hall, Dublin, on Friday, in association with Anglo Irish Bank. The concert also features the world premiere of Stephen Gardner's Hassan, Mozart's Violin Concerto K219(with soloist Chloë Hanslip), and Ravel's La Valse