Back in the day, St. Anne and St. Agnes, in the heart of the City of London, numbered among its parishioners John (Paradise Lost) Milton, John (Pilgrim’s Progress) Bunyan, and John Wesley, the Methodist trailblazer. Rebuilt on the plan of a Greek Cross by Sir Christopher Wren in 1680, the church is now home to the VOCES8 Foundation, which pursues its mission through music education. Responding to the need of performers to get back to work as well as to the audience’s hunger for live experience, VOCES8 has summoned 10 of the world’s preeminent a cappella ensembles to St. Anne and St. Agnes for an online celebration of exquisitely tuned vocalism. The home team VOCES8 leads the way, followed by such varied headliners as Apollo5, Gesualdo Six, The Sixteen, Stile Antico, Chantecleer, and the Swingles. —M.G.