Pellegrin situated the second act in the Underworld, following the example of Lully's "Alceste" (1671), "Isis" (1674), and "Proserpine" (1680), as well as later works by Desmarets, Marais, and Destouches. "Isis", which had been revived on 14 December 1732, was particularly important for Pellegrin as it had a trio for the Fates. The dark colour of this act is enhanced by the use of solely male voices. There are lively and rhythmically inventive dances for the demons contrasted with Thésée's moving invocations to save the life of his friend Pirithous in music in which "the expression of the sentiment is cut down, as it were, to the bone". The act concludes with the famous and controversial second "Trio des Parques", omitted from the premiere because the Opéra's singers and instrumentalists found it too hard to play. It makes use of enharmony, a technique Rameau believed was ideal for "inspiring dread and horror".