Experience two ensembles at the top of their craft performing together. Downtown Voices and chamber chorus Amor Artis take on a set of monumental works: Frank Martin’s Mass for Double Choir, a deeply spiritual and intricate composition; Thomas Tallis’s Spem in Alium, a 40-part Renaissance motet; and Orazio Benevoli’s Missa Tu es Petrus (for four choirs), featuring opulent Baroque textures and counterpoint.