L’Apothéose de Lully was Couperin’s hommage to his great musical predecessor and depicts the elder composer’s elevation to Mount Parnassus (where he plays duets with the shade of Corelli and, with Apollo’s blessing, effects a reconciliation between the contrasting French and Italian styles of the day). The Leçons de ténèbres were written for performance in Holy Week and demand—and here receive from Katherine Watson and Anna Dennis—vocal artistry of the highest order.