Wikipedia
Prométhée (Prometheus) is a tragédie lyrique (grand cantata) in three acts by the French composer Gabriel Fauré with a French libretto by Jean Lorrain and Ferdinand Hérold, based on the Greek myth of Prometheus. The first performance at Arènes de Béziers on 27 August 1900 involved almost 800 performers (including two wind bands and 15 harps) and was watched by an audience of 10,000. Between 1914 and 1916, Jean Roger-Ducasse reworked the score for a reduced orchestra. This version (which was later revised by Fauré) made its debut at the Paris Opéra on 17 May 1917 but never became popular.
Designated as a tragédie lyrique, the work resists easy categorisation. It was intended to be on a large-scale with spoken and musical sections. Warrack & West call it a grand cantata, arguing that since "only some of the characters participate in the stage action it is scarcely an opera, though Fauré's conception of the work is at times more operatic than merely choral ... [and] the clearest example to date of Wagner's influence on his music."