Picks from across the week on In Tune with Sean Rafferty. His guests this week include the world renowned a cappella group The King's Singers, celebrating its 50th anniversary this year. Tenor James Gilchrist and pianist Anna Tilbrook reflect on 20 years working together, and Kyra Humphreys celebrates two decades with the Royal Northern Sinfonia. Plus choreographer Frank Andersen, one of the world's leading experts on Bournonville ballets.