Preview: Zaide, Barbican, London

A fable about freedom and forgiveness

This is Mozart according to that perennially provocative director Peter Sellars, who, with the conductor Louis Langrée, has taken the surviving fragments of Zaide - the opera Mozart wrote when he was 23 but never lived to hear - and interwoven them with fragments of Thamos, King of Egypt, written by him in the same year, and also not heard in his lifetime.

Since all that remains of Zaide are the arias, the original connecting dialogue of this singspiel has been replaced with mimed action. The plot is simple: the overseer Allazim is persuaded to help the captives of Sultan Soliman escape, the Sultan vows revenge but in the last moments is softened by divinely inspired remorse.

The arias are both beautiful and daringly inventive, with a superb multiracial cast of relative unknowns led by a lustrous-voiced Korean soprano, Hyunah Yu. The final quartet ends in a musical suspension of such suddenness that one is left wondering - what next?

And in Sellars's view that is precisely what Mozart intended: he regards this opera, which many others have "completed", as - barring the missing dialogue - complete. Mozart, he says, was simply ahead of his time. "Here is a demanding 23-year-old who wants to challenge the world, saying, 'Don't you see this is wrong?' The outrage is palpable. The utopianism of the first act's libretto might have been written by Martin Luther King, with aria after aria about liberation."

And it all hinges, he says, on its final question: will there be mercy? For Sellars this opera, which turns on the relationship between Christian and Muslim worlds, is as contemporary as it was in 1779. "Look at this morning's news from Gaza, and from Baghdad. Will those conflicts be carried on to the point where one side is obliterated, or will there be mercy? That's going to be the overriding question in the 21st century. Mozart stopped there, because there wasn't an answer yet. He couldn't round things off with a neat wedding-cake aria then - any more than he could now. He leaves us with the feeling that something actually could happen next - and that that would be a key moment."

6 July (020-7638 8891; www.barbican.org.uk)