Sofia Gubaidulina 's music packs a powerful punch that defies her Soviet roots, writes Michael Dervan.

Sofia Gubaidulina will be 75 next October. But you wouldn't know it from the spring in her step or the sharpness of mind she showed in public interviews when she attended A Journey of the Soul, the festival of her work presented at the Barbican in London over the weekend by the BBC Symphony Orchestra.

Gubaidulina was born in Chistopol in the Tatar Autonomous Republic in 1931. There was nothing in her grey surroundings to excite a child - no toys, nowhere to play. So she looked upward and found inspiration in the sky. She discovered religion in an anti-religious milieu, and the response of adults to her excitement told her that she needed to keep her new-found interest private. When a piano and piano lessons finally arrived in her life she found the early learning restriction to the centre of the keyboard so limiting she knew she would have to compose her own music to get around it. And music, somehow, merged naturally with religion.

Trouble was inevitable for a composer of her bent working within the constraints of the Soviet Union. She could well have even found herself in hot water through the works she submitted for her graduation. But Shostakovich was on the examination panel, and defended her.

"Everybody thinks that you are moving in the wrong direction," he told her. "But I wish you to continue on your 'mistaken' path."

That mistaken path forced her into the familiar fate of misfit composers of making a living through other than her primary interest. She wrote music for films and for the theatre. But she was also able to spend time in a studio for electronic music, and set up an improvising trio with fellow composers. Like the similarly marginalised Alfred Schnittke, she absorbed from everything she did. And, like so many composers from the margins of Soviet music, when she emerged into Western consciousness it was as a mature figure, surprisingly well versed in the complex sonorities of the Western avant-garde and using them to spiritual ends that were entirely alien to Soviet ideals.

The sky and the earth, the light and the dark, the spiritual and the mundane are the concerns that Gubaidulina's music speaks of. The world tremors in her work, and the pure, high sounds of redemptive heaven also beckon. She is greatly interested in the minutiae of sound production. She has, for instance, taken to the Russian accordion, the bayan, made it groan and gasp, and dared write a concerto pitting it against a full orchestra. She beat Steve Reich to the idea of combining live and pre-recorded string quartets. She has embraced the challenge of composing lighting patterns for particular pieces, following up on an idea first given currency in the early years of the 20th century by another Russian, Alexander Scriabin.

Hers is a world of paradox. The full panoply of contemporary compositional technique is hers. Yet she elaborates the simplest of ideas with the most complex of textures, often seeming to expand a single note by a kind of slowly executed refraction. She seems to want to extract the innermost secrets of a vivid moment and make music by trailing them through time.

The results can be both absorbing and tortuous. Gubaidulina's sense of time allows her to mull over her material at great length, to explore repeatedly the juxtaposition of her favourite oppositional concerns. If the procedures do not grip, they can create for the listener a sense of merely waiting rather than a sense of expectancy, the disorientation of following an unfamiliar ritual rather than any more pleasurable anticipation.

At its best her music packs a powerful punch. Her choral orchestral Alleluia of 1990 sets just one word, the title itself, in four of its seven movements. But the narrowness of the focus and the obsessiveness are fully warranted by the surging forces within the music. And the lightening to a group of solo boy treble voices at the end is also wholly effective. The Hour of the Soul (1974) is a similarly lopsided setting of part of a dark poem by Marina Tsevtaeva, a daunting wind ensemble (no less than 14 clarinets) is taken to extremes that leave the listener shattered even before the words are treated with haunting and all the more devastating simplicity at the end.

Paradoxically, I suspect, Gubaidulina's work is not best served by the concentrated juxtapositions of even a three-day festival - at her own insistence, only Bach, Schütz and Haydn rubbed shoulders with her music over the weekend, and then only in small quantities.

Her breakthrough work, the violin concerto, Offertorium (1980), played with irresistible concentration by Leonidas Kavakos and the London Symphony Orchestra under Michail Jurowski, was deeply stirring. And The Canticle of the Sun, for cello, percussion and choir, was memorable for Alexander Ivashkin's upward cello surges, bursting with a kind of wordless ecstasy.

But, in spite of consistently high performance standards, many of the weekend's other works, like paintings that need uncluttered space, seemed to call for different surroundings, a setting of greater contrast and isolation, to make their maximum effect.