(This episode is available for streaming on Oct. 13 only.) The Jason Max Ferdinand Singers are among the world’s leading African American choirs, and this week, you’ll hear their debut concert at the BBC Proms. There’ll also be highlights from an exciting new double album from the Toronto Mendelssohn Choir and their director, Jean-Sébastien Vallée. Plus, selections from Luminous Voices, the Elora Singers and the Thirteen.