Two of the world’s most distinctive vocal ensembles — VOCES8 and the Swedish barbershop champions Ringmasters — join forces for a program that moves effortlessly from Renaissance polyphony and Romantic choral works to folk song, contemporary composition, and iconic popular repertoire. Alongside music by Gabrieli, Rachmaninov, Praetorius, and Whitacre sit imaginative arrangements of Loch Lomond, The Fool on the Hill, …