Raider of musical history

When Alfred Schnittke died at the age of 63 in 1998 after his fifth stroke, he left behind a partially-completed and scored work, commissioned by the London Sinfonietta. The premiere of this Fragment was strategically placed at the heart of the 10-concert all-Schnittke Festival, Seeking the Soul, presented at the Barbican Centre in London last weekend by the BBC Symphony Orchestra, as "the first major retrospective since the composer's death".

Schnittke was interested, Mahler-like, in putting the world into his music. And for a long time his regular musical world was that of the film industry, where he made a living - and scored more than 60 films - while his work was excluded on ideological grounds from the normal concert outlets of Soviet musical life.

His experiences in the realm of film, and in particular his work on Mikhail Romm's The World Today, a documentary survey of 20th-century history, seeped, indeed sometimes exploded, into his other work. His First Symphony of 1972, the earliest piece included in the BBC survey, is a polyglot, cornucopian tapestry of outrageous juxtapositions, ranging across the musical spectrum from jazz to mockbaroque, and with theatrical parading of musicians on and off the platform, bringing the antics of Haydn's Farewell Symphony on to a new level.

If all this sounds in description to be a bit over-the-top, that's probably because it is. Schnittke may have felt his German roots to have been crucial to his musical character - he was born into a German-speaking family in the Autonomous Soviet Republic of the Volga Germans - but there's a grandness of manner and an overt, soul-baring emotionalism in his work which seem to ally him firmly to Russian tradition.

In what he completed of the London Sinfonietta commission, three movements from a projected, five-movement cantata for countertenor, the familiar profligacy was replaced by music of greater focus and restraint. Here, in writing that was bold and precise of gesture, there was no sense of the familiar Schnittke clutter. The composer, whose last 13 years were marred by a series of debilitating strokes, told associates that one of the effects of his condition was that individual notes had become richer to him and that his sense of time had changed. This may well account for the paring down, but it's hard not to feel that the special physical challenges he faced must have played a role: in order to continue composing, he had to learn to write with his left hand, and he continued to compose after one of the strokes deprived him of speech.

The late Concerto a 3 of 1994, for violin, viola, cello and strings, shows signs of related restraint: an economic concentration on working with instrumental subgroupings, expressive goals achieved by subtractive rather than the earlier additive means. And this impressive piece ends with an almost filmic coup: a violent, out-of-nowhere cluster on piano, felt by some to be a ghastly premonition of his next stroke. The cluster was no less striking when transferred in the London Sinfonietta's performance, to the organ of St Giles, Cripplegate, where most of the festival's smaller-scale concerts where held.

The programmes embraced five of his nine symphonies and four of his six concerti grossi. Appropriately enough, it is probably the second movement of the cumbersomely titled Concerto Grosso No 4/Symphony No 5 - a hybrid work which finds a place in both canons - that perhaps highlights most effectively some of the key processes of the composer's thinking. It's an orchestral canvas after an early piano quartet by Mahler and, is as revealing of its composer as, earlier in the 20th century, was Webern's orchestration of Bach.

Inevitably, Schnittke is not an easy composer to pin down. The Russian Orthodox-influenced Concerto for Mixed Choir is a daunting, 45-minute sing in a manner of unreconstructed expressionism, one of the more surprising products of a troubled, burdened soul with a rare and freely exploited arsenal of stylistic and expressive outlets. It stood at the opposite end of the festival - and as an opposing pole - to the altogether too cheap, if effective, grotesquerie of the closing Faust Cantata.

The festival was graced with the presence of some of the finest advocates of Schnittke's music, most notably the violinist Gidon Kremer, rhythmically tight, coolly passionate and intricately characterful, the Estonian conductor Eri Klas, who handled the crowded canvasses without, as it were, any unwanted blurring or bleeding of colour, the composer's widow, Irina, a pianist of awesome power and insight, and the ever-adaptable BBC Symphony Orchestra. Overall, this was a remarkable celebration of a man who, at least until the very end of his life, might almost have had as his musical motto that dangerous line from Blake: "The road of excess leads to the palace of wisdom."