Advent Calendar: 20 December

O Key of David and sceptre of the House of Israel;you open and no one can shut;you shut and no one can open:Come and lead the prisoners from the prison house, those who dwell in darkness and the shadow of death.

The plainsong of this verse is sung by a solo voice, followed by a meditation on the text for organ by contemporary American composer Nico Muhly, played by James McVinnie.