The climax of the Proms Reformation Day is a complete performance of Bach’s St John Passion. ‘More daring, forceful and poetic’ than the St Matthew Passion, according to Schumann, this is a work of almost operatic vividness that brings both a humanity and a painful immediacy to the Passion narrative. Bach specialist John Butt and his Dunedin Consort make their Proms debut in a performance that offers the audience the chance to join in the chorale-singing, reflecting how the work might originally have been heard in a church setting.