Scottish Chamber Orchestra/Lyell Cresswell, SCO/Royal Scottish Academy of Music and Drama, Glasgow

You have to admire Lyell Cresswell's ambition. Sixty next year, this New Zealander long settled in Scotland has taken the theme of exiles for his startling new work Shadows Without Sun. As well as drawing on largely anonymous recorded material of exiles relating their experiences of living in Scotland, he has also made a feature of the life and letters of the "rebellious and bloody-minded" sectarian Scots preacher Norman McLeod, exiled in New Zealand. And as if that wasn't already enough material, the composer adds the tragic story of the Greek heroine, Cassandra. You hardly need to be a prophetess to guess that this is at least one dimension too many.

But this is, after all, the Scottish Chamber Orchestra's innovative "Adventurer" series and, funding having been available in the form of a "Creative Scotland Award", Cresswell has taken the opportunity to create a work as improbable as shadows themselves are without sun. A hybrid - neither oratorio nor opera, neither music theatre nor cantata - Shadows Without Sun is a sort of docutata, with the assorted voices of the exiles adding a poignant if often incomprehensible commentary.

The mezzo-soprano Catherine Wyn-Rogers gave a deeply eloquent interpretation of poems by Ron Butlin as well as a couple of Yoruba songs and a few verses from the Scottish Psalter. In the role of narrator, as well as reading extracts from Euripides, Ian McDiarmid brought another Lord of the Dark Side to vivid life in snapshots of McLeod's hard time in exile and his trenchant opinions.

The orchestra, ably conducted by Garry Walker, plays the role of the chorus, commenting on and illustrating the words, consoling and also fulminating against the injustices told by these assorted exiles across the centuries. The instrumental writing is beautifully evocative. To the words "By day my heart's a language I cannot speak" the strings stutter helplessly; to the winter cruelty suffered by McLeod and his followers the instruments bring a freezing intensity. In the bracing "Norman McLeod's Dances" the SCO played with suppleness, capturing the manic "Tam O' Shanter-ish" quality of the music's changing textures. Haunting solo wind playing, austere brass, sinister strings and a subtle theatricality distinguish the orchestra's role as supporting actor and provider of incidental music.

Some of the pre-recorded material is very moving, especially the Chilean woman's description of being terrified twice, once under Pinochet's regime and again in Britain where she has again become a prisoner in her own home. But too much of it is unfocused. At nearly 90 minutes the work is too long. It needs drastic cutting and possibly restructuring to give those shadows cogent shape.