Theatre The Mystery Plays City of London Festival

Medieval mystery plays and African-American spirituals have a lot in common. Both are essentially working-class traditions in which - it's hard to discuss this without dropping into rather creaky crypto- Marxist language - Bible stories are appropriated from the ruling classes and subverted into egalitarian fables. There are contrasts (the emphasis in the mysteries is all on the Manichaean struggle between good and evil, while the spirituals lean more towards stories of liberation, and a theology in which death is a release from the burden of this world); but they're outweighed by the shared narrative verve and populist morality.

All of which makes Richard Williams's hugely enjoyable version of The Mystery Plays, punctuated by Joanna MacGregor's arrangements of spirituals, seem a little out of place within the City of London Festival. At Sunday's performance in the Priory Church of St Bartholomew the Great, there were even free copies of Harpers & Queen on hand for the audience.

As it turns out, "spirituals" is a deceptively simple term for the range of styles MacGregor adopts, from call-and-response field songs to the sophisticated harmonies and rhythmic virtuosity of Forties-style doo-wop and contemporary gospel. The songs serve all kinds of purposes within the action, sometimes acting simply as between-scene punctuation, sometimes drawing your attention to the themes buried in the drama - the repeated use of the song "The Book of the Seven Seals" is a neat way of drawing attention to the way that the mysteries present all these disparate stories as moving towards the same predestined conclusion. As well as the spirituals (beautifully sung, for the most part a cappella, by the nine-strong cast), MacGregor uses a variety of percussion effects to underscore the action, in ways that often echo Britten's church parables. The music's eclecticism is matched by the diversity of approaches in Richard Williams's highly condensed translation of the mysteries into modern English, which conflates a number of versions and dips into and out of metres and styles: there's alliterative verse, rhyming couplets, either straight or disrupted by internal rhymes and abbreviated metres, straight church-flavoured prose and, for the more comic episodes, some unconvincing modern vernacular.

There's a sometimes intrusive sense of pastiche; and perhaps that's why on Sunday evening the episodes which should be most moving - the Fall of Man, the Crucifixion - fell short. It doesn't help that some of the cast aren't ideally equipped for this kind of drama or music. The shortcomings, though, are made up for by the vim of the ensemble playing, and by Williams's staging, which uses the long, narrow space of St Bartholomew's nave to intelligent effect. There are some excellent individual performances, too - Paul Ryan's twitchy, sensual Lucifer, Martin Nelson's slow-speaking Abraham, Amanda Symonds's gospel singing. And Clive Rowe is outstanding, switching easily between a powerful, thrilling bass and a touchingly delicate falsetto, between broad comedy and high drama. The evening may lack emotional depths; but it certainly has its share of highs.

Further performance on Sun. Booking: 0171-638 8891