Plot: Conductor Dalia Stasevska and the BBC Symphony Orchestra kick off a six-week season with Vaughan Williams’s ravishing Serenade to Music and Poulenc’s dazzling Organ Concerto. They’re joined by the BBC Singers and a cast of soloists, including soprano Elizabeth Llewellyn, tenor Allan Clayton and organist Daniel Hyde, for a celebration of the power of music to comfort and lift your spirits