sentences:  Calzabigi originally wrote the libretto of "Les Danaïdes" for Christoph Willibald Gluck, but the aged composer, who had just experienced a stroke, was unable to meet the Opéra's schedule and so asked Salieri to take it over.The plot of the opera is based on Greek tragedy and revolves around the deeds of the mythological characters Danaus and Hypermnestra.Emperor Joseph II assured that Salieri wrote the music "almost under the dictée of Gluck," in a letter (dated 31 March 1783) to Count Mercy-Argenteau, the Austrian ambassador in Paris.