For a composer who made a big splash as long ago as 1978, Gloria Coates has had to wait a long time for her music to come to Ireland.Gloria Coates tells Michael Dervan how she came to realise thatmusic was more important to her than her life

That big splash came at the Warsaw Autumn Festival of 1978, when her Music on Open Strings of 1973 was premiered at what was then the most important musical crossing point on the ideological divide between the countries of the communist Eastern bloc and those of the capitalist West.

The annual Warsaw festival was a major event in the world of new music, and the ripples from Coates's success were felt back in the West, in her adopted city of Munich. Music on Open Strings was featured in Bavarian Radio's prestigious Musica Viva series in 1980, the first time in its 35-year-history that the series had presented an orchestral work by a woman.

It's within the past 10 years, however, that Coates's profile has developed outside of the rather rarefied circles of events specialising in the advocacy of new music.

Two CDs of orchestral music appeared on the German label cpo, and her entire output of eight string quartets has been issued on two discs by Naxos. It's through one of those quartets, the Sixth of 1999, that the Crash Ensemble will introduce her music to Irish audiences on Thursday.

There's an old story told about Grieg that might well be applied to Coates. The young Grieg, it is said, was making up chords at the piano, and he discovered one particular combination that he liked so much he went on to use it in everything he wrote. Coates is celebrated for her use of glissandos, sliding sounds, which she made an entire piece out of as a young composer, to the great dismay of her teacher.

In Coates's work glissandos are not used merely for their momentary emotional effect. They often occupy the foreground, moving in a slow-motion manner that enables her, as it were, to uncover their unsuspected inner nature, much as a slow-motion replay of a smile, a blink, or a movement of the hand can suggest subtleties of meaning and inflection that simply can't be caught at normal speeds.

The slow glissandos aren't Coates's only trademark. She's fond of those dissonant fistfuls of notes known as tone clusters. She likes to use microtones, which call on players to subdivide the notes of the conventional scale. And she has made it into the record books by writing 14 symphonies, which fellow composer and critic Kyle Gann, having scoured the encyclopaedias, believes is a world record for a woman in the still male-dominated field of symphony writing. She's also a painter (you'll find her work on the covers of her CDs), and was for many years involved in a concert series promoting new music from Germany and America in Munich.

I met the 66-year-old composer on a beautifully sunny spring morning in snow-covered Munich in her new apartment (previous occupant film director Leni Riefenstahl, maker of Nazi documentaries), the walls hung with Coates's paintings, the view encompassing many of the city's famous spires, the arrangements - even the seating for the formal interview - made on feng shui principles.

There's a severity, a rigour, a grittiness in much of Coates's music which is completely at odds with her outgoing amiability as a person. She was born and brought up in Wausau, Wisconsin, and remembers her first contact with music being through a toy piano at the age of two or three.

Her mother told her of a dream of playing a piece of her own on the toy piano, and this fired young Gloria's imagination to do the same. When she started having piano lessons she persisted in exploring her own sound world "which was not what I was being taught," and she used to buy marked-down copies of the great classics (which at the beginning she was also not being taught) at local five-and-dime stores.

By the age of 12 she found that other people were interested in her experimental playing. She never thought of it as improvisation, and she modestly invented a Russian with a name ending in -ski to identify as the composer. She was, however, encouraged to keep pencil and paper by the piano so that she could write things down if she wished.

She successfully entered a National Federation of Music Clubs Composition Contest, although the best advice she could get had her change the piano clusters in her song accompaniment to regular arpeggio patterns. Clusters, it seems, were not covered in any theory book the local organist knew about.

She won the competition, but was upset at the enforced changes. Her corner of the mid-west was not up to speed on new music, and it was in the Q&A after a lecture in Milwaukee by the Russian composer Alexander Tcherepnin that the teenage composer was finally given some kind of official licence to follow her instincts. If she could hear it and play it and write it, Tcherepnin assured her, she didn't need to justify it with a theoretical backup.

Tcherepnin became an important mentor. "All my life, as long as he lived [ he died in 1977], he was amazingly encouraging." And from what she says, she must have needed all the encouragement she could get. "Where I grew up, at the time I grew up, you could never write serious music as a profession. Gershwin was the closest you could be. I had examples of women writing songs, yet it wasn't a profession. In high school, we had to write what we were going to be when we left school. I never said composer, but I think I said musician, and I was told you can't be a musician on your own, you'll have to teach it. Then I switched to artist, and they said you can't be that either, you'd have to be a commercial artist."

She supported herself through college - if she failed she wanted it to be a failure of her own, not a family trauma -and was as active in the theatre and with painting as she was with composition. Although she ended up with a master's degree in composition, she explains that this happened "because I had been interested in all those courses" rather than because she had any intention to acquire a training as a composer.

Although she received plenty of encouragement, she explains, "I'd always run away from this thing of being a composer", until something happened to make it clear quite how central composing was in her life.

Recalling that crucial moment, she becomes overcome with the flood of emotion, finds it difficult to get the words out, needs to wipe away her tears. She had moved from the US to Europe. She had married and had a daughter, but was now divorced. She was active enough as a singer to have had an agent in Vienna, but composition was still on the agenda. And she was expecting the relocation to enable her develop "a whole new perspective on life".

When the building she was living in Munich was believed to be under terrorist threat - it was the era of the Baader-Meinhof Gang and the terrorist attack at the 1972 Olympic Games - she moved out her music manuscripts and made arrangements for their protection. But she continued to live in the building with her birds and her paintings - her daughter at the time was with her father in the US.

She can hardly speak the words as she says, "It was not until several months later that I realised that that music was so important, it was more important than my life."

She's still in wonder at the revelation as well as upset by it. "Those were just simple pieces. One was a flute trio, one was a string quartet." When she recovers her composure she finds an explanation for her inner turmoil. She was always happier, she explains, when she was involved in acting or painting. "Composing comes from this other place. Time goes by quickly, and what happens is that I no longer have a life of my own. It's a life of dedication. I guess I miss all those other things. That's part of it. And yet I have no choice. I have a choice. I've had a choice, all the time, and have had many choices. But somehow I have to always do what's the real honest me. And that's it."

The explanation ison the one hand simple and direct, yet with ramifications that are extremely far-reaching. And it's presented with disarming matter-of-factness. It's the moment in the interview in which the quiet-spoken, talkative, companionable composer comes closest to the often extraordinarily demanding music she writes.

Underlying the music you'll often find spare and rigorous canonic structures that show her long-standing reverence for Bach.

On the surface you'll hear sounds that fearlessly create a tension that's at times almost unbearable. Coates is one of those composers who is as ready to deal with the inexorable demands of her musical material as she has been to confront the difficult imperatives of music in her life. Bleak and ascetic, strange and disturbing as her music may be, it's also got a purity that makes it peculiarly compelling. It's not music that's ever likely to leave even a single listener indifferent.

The Crash Ensemble perform Gloria Coates's Sixth String Quartet (1999) at the O'Reilly Theatre, Great Denmark Street, on Thursday in a programme that also includes works by Helmut Lachenmann, John Adams, Yannis Kyriakides and Louis Andriessen, 01-8711122