Io is an unfinished opera by Jean-Philippe Rameau in the form of a one-act acte de ballet. The date of its composition is unknown and it was probably unperformed during Rameau's lifetime. Its unfinished state meant that it was once believed to be Rameau's last opera, but Io contains a duet which appears in revised form in Les fêtes de Polymnie (1745). This has led the musicologist Graham Sadler to conclude that Io must predate 1745 and that the librettist was Louis de Cahusac, who also wrote the words for Les fêtes, because French librettists did not borrow from other writers.
|Jupiter, under the name of "Hilas"|
|Apollon (Apollo), under the name of "Philémon"|
|La Folie (Madness)|
Mercury warns Jupiter that his jealous wife Juno is approaching. Jupiter tells Mercury his new love is the young nymph Io, whom he plans to seduce in the guise of a shepherd, Hylas. He has a rival in the god Apollo, who has also been wooing Io, disguised as the shepherd Philemon. Io enters and tells "Hylas" that she prefers him to "Philemon", but when Philemon expresses his despair she feels sorry for him. A storm breaks out. When Jupiter conjures it away, Io realises that "Hylas" must be a god and Jupiter at last reveals his true identity. The two declare their love for each other.
In the next scene, La Folie (Madness) announces that Apollo has abandoned Mount Parnassus and she has taken advantage of the chaos to steal his lyre. At this point, the opera breaks off.
- Sadler (2014), p.109
- Girdlestone, Cuthbert, Jean-Philippe Rameau: His Life and Work, New York: Dover, 1969 (paperback edition)
- Holden, Amanda (Ed.), The New Penguin Opera Guide, New York: Penguin Putnam, 2001. ISBN 0-14-029312-4
- Sadler, Graham, (Ed.), The New Grove French Baroque Masters Grove/Macmillan, 1988
- Sadler, Graham The Rameau Compendium (Boydell Press, 2014)
- (French) Libretto at "Livrets baroques"