Plot: Katie Derham reviews the sixth full week of Proms activity in this penulitimate episode of Proms Extra. She is joined by jazz saxophonist Soweto Kinch and conductor John Butt to discuss Bach's St John Passion, performed in week five of the Proms by John Butt's Dunedin Consort, and the Charles Mingus Prom, featuring Kandace Springs, Shabaka Hutchings and Christian Scott