The overture depicts a storm during which Jupiter hurls Apollo from heaven as punishment for mocking him. Apollo disguises himself as a shepherd under the name "Alexis". His singing attracts the attention of the farmer Palemon. Palemon is a music lover and offers Apollo a job. He explains that the local bailli (magistrate) Midas has arranged marriages between Palémon's daughters Lise and Chloé and two other musical talents from the village, Pan and Marsias. Apollo is appalled at the quality of their singing. Paleon's wife Mopsa reproaches him for taking in a stranger, "Alexis", without knowing anything of his background.
Act 2
Lise and Chloé discuss the attractions of the newcomer. Apollo also manages to charm Mopsa and begins to court both daughters. Soon Palémon and Mopsa are persuaded that he would make a better son-in-law than Pan or Marsias and they plot to get rid of them.
Act 3
Midas is annoyed at the turn of events. He decrees that the choice of husbands will be decided by a singing contest. He completely rejects Apollo's new style of music, preferring Marsias's piece in the style of old-fashioned French Baroque opera and Pan's in the style of popular vaudevilles. Apollo responds with an allegorical song describing a competition between a nightingale, owl and cuckoo judged by a donkey. Midas is outraged at the insinuation and banishes him but Apollo punishes Midas by giving him donkey's ears. The god then reveals his true identity. Mercury descends from heaven to announce Jupiter has forgiven Apollo, who sets off for Parnassus with both daughters in tow.
Le Jugement de Midas: Louis Devos, Jean-Jacques Schreurs, Bernadette Degelin, Loretta Clini, Chris de Moor, La Formation de Chambre du Nouvel Orchestre Symphonique de la RTBF, conducted by Ronald Zollman (Koch Schwann 3-1090-2) (extracts)
^Sources will refer to this singer stating simply his surname 'Narbonne'. Émile Campardon does not report any first name in his work on the 'comédiens italiens' (Les Comédiens du roi de la troupe italienne pendant les deux derniers siècles: documents inédits recueillis aux Archives Nationales, Paris, Berger-Levrault, 1880, article: Narbonne, II, p. 29, accessible for free online at Internet Archive), whereas the name 'Pierre-Marie' is set forth in his later book on the Académie Royale de Musique, where Narbonne began his career (L'Académie Royale de Musique au XVIIIe siècle, Paris, Berger-Levrault, 1884, II, p. 193). The name 'Louis' is given instead by Georges de Froidcourt in his collection of Grétry's correspondence (La correspondance générale de Grétry, Bruxelles, Brepols, 1962, p. 145, footnote 8).
Sources
Public premiere libretto: Le jugement de Midas : comédie en trois actes ; en prose mêlée d'ariettes ; représentée pour la premiere fois par les Comédiens Italiens ordinaires du Roi, le Samedi 27 Juin 1778, Paris Duchesne, 1778 (accessible online at Library of Congress)