In 1854, Hector Berlioz confided in his memoirs that, “For three years, I have been tormented by the idea of a vast opera for which I would like to write both words and music.” Held back by the failures of Benvenuto Cellini and La Damnation de Faust, the composer was to wait another two years before throwing himself into Les Troyens, an enterprise based on Virgil’s Aeneid: an a...