 He followed Anne-Jules, 2nd duc de Noailles to Spain as his secretary.His talents gained him a pension from Madame de Maintenon, and a commission from her for Vancy and Jean Racine to compose sacred poems, edifying stories and religious tragedies for the maison de Saint-Cyr ("Absalon", "Jonalhas", "Débora").Vancy also wrote opera librettos modelled on Racine, the best known of which were "Céphale et Procris" and "Iphigénie en Tauride" (the latter with additions by Antoine Danchet).