The hall is keeping the particulars of the program under wraps, disclosing only that it will run about an hour without intermission and feature the music of Barber, Bernstein, Copland, and more. Take the leap of faith. Over the decades, the Jamaican-born British bass baritone, now in his seventies, has proved an artist of unflagging radiance in repertory from Gershwin’s Porgy to Mussorgsky’s Boris Godunov. We’d gladly listen to him sing the phone book, as the saying goes, but we’re sure he has better things up his sleeve. —Matthew Gurewitsch