NICOLA LeFanu, music professor at the University of York, presents her BBC Radio 3 commission, Light Passing, in the National Centre for Early Music, York, from Thursday to Saturday.

The centre, in St Margaret's Church in Walmgate, is an apt medieval setting for a chamber opera that relates the life story of Pope Clement VI, most brilliant of the Avignon Popes in medieval France.

"To date there has been no portrayal of his life and I welcomed the challenge and opportunity of bringing him to life," Nicola says.

Explaining the Light Passing title, she says: "Clement VI lived in the 14th century, and as a spiritual leader he preached tolerance, defending the Church from bigotry and ant-Semitism, during the crisis of the Black Death, and he was a tremendous patron of the arts too. That seemed important, as well all need our patrons.

"Light is important for many reasons: Clement's light is passing because he dies at the end; there is the light of Christianity or faith, and then there is 'light' meaning freedom or tolerance, because although the opera is set in the past, it deals with issues that we face today."

Clement VI combated religious fundamentalism, Nicola says: "When people blamed the Jews for the Black Death, he issued a law protecting Jews and said people of all religions were equal in the eyes of God. If ever there were a message relevant to today, that is it."

Nicola's score weaves together her new music with 14th century French polyphony and plainchant.

Bass baritone Nicholas Folwell sings the role of Clement VI; counter tenor Nicholas Clapton is the Flagellant leader/Novice master; Christopher Lakin is young Clement and fellow York Minster chorister Benedict Rowe plays the Altar Boy.

They will be joined by young singers and instrumentalists from the Royal Liverpool Philharmonic Orchestra's Ensemble 10/10, conducted by Clark Rundell, plus harpist Lucy Wakeford and percussionist Damien Herron.

Light Passing, National Centre for Early Music, York, Thursday to Saturday, 8pm; tickets £3.50 to £20 on 01904 658338. BBC Radio 3 will broadcast this world premiere on November 27, 10pm.

Updated: 09:45 Friday, October 22, 2004