“Lessons of darkness” is the generic term for French Baroque liturgical music for the first three days of Holy Week. The texts are from the Lamentations of Jeremiah, and while the idiom is inspired by polyphonic Italian models from the Renaissance, the music is for solo voices. On April 1, William Christie and Les Arts Florissants do the honors in compositions by Marc-Antoine Charpentier. On April 5, Gaétan Jarry conducts from the organ this companion program of music by François Couperin. —Matthew Gurewitsch