Question: Between Rienzi and Iphigénie en Aulide, which premiered earlier ?
Context: Nicolas-François Guillard (16 January 1752 – 26 December 1814) was a French librettist.  He was born in Chartres and died in Paris, the recipient of a government pension in recognition of his work writing librettos.  He was also on "Comité de Lecture" of the Paris Opéra.  One of the foremost of the French librettist of his generation, he wrote libretti for many noted composers of the day, including Salieri ("Les Horaces") and in particular Sacchini ("Oedipe à Colone", amongst many others).  His most famous work is "Iphigénie en Tauride", his first libretto, set by Gluck after the composer had initially rejected it.  Gluck collaborated with Guillard to heavily recast the libretto, not only to suit Gluck's artistic preferences, but also to accommodate pre-existing music that Gluck borrowed, both from himself and from other composers, when composing the opera. Iphigénie en Tauride (English: "Iphigeneia in Tauris") is an opera by the French composers Henri Desmarets and André Campra.  It takes the form of a "tragédie en musique" in a prologue and five acts.  The libretto is by Joseph-François Duché de Vancy with additions by Antoine Danchet.  Desmarets had begun work on the opera around 1696 but abandoned it when he was forced to go into exile in 1699.  Campra and his regular librettist Danchet took up the piece and wrote the prologue, most of Act Five, two arias in Act One, an aria for Acts Two and Three, and two arias for the fourth act.  The plot is ultimately based on Euripides' tragedy "Iphigeneia in Tauris". Styled a "festa teatrale", "Le feste d'Apollo" consists of a prologue and three self-contained acts on the model of French "opéra-ballet" (the court of Parma was passionately interested in French culture).  Gluck knew the Archduchess Maria Amalia well as she had sung in two of his operas, "Il Parnaso confuso" and "La corona", in Vienna.  The composer recycled a lot of music from his earlier operas in the score of "Le feste".  In fact, the whole of the third act, "Orfeo", is a shorter reworking of his most famous piece, "Orfeo ed Euridice" (1762).  The overture to the prologue is taken from "Telemaco".  Gluck later reused some of the choruses in two of the operas he wrote for Paris, "Iphigénie en Aulide" and "Iphigénie en Tauride". François-Louis Gand Le Bland Du Roullet (10 April 1716 in Normanville – 2 August 1786 in Paris) was a French diplomat and playwright.  He is chiefly remembered today as the librettist of Gluck's operas "Iphigénie en Aulide" and "Alceste" (1776 French version).  He also co-wrote (with Louis-Théodore de Tschudi) the libretto for Salieri's opera "Les Danaïdes". Rienzi, der Letzte der Tribunen ("Rienzi, the Last of the Tribunes"; WWV 49) is an early opera by Richard Wagner in five acts, with the libretto written by the composer after Edward Bulwer-Lytton's novel of the same name (1835).  The title is commonly shortened to Rienzi.  Written between July 1838 and November 1840, it was first performed at the Hofoper, Dresden, on 20 October 1842, and was the composer's first success. The Mecklenburg State Theatre (German: "Mecklenburgisches Staatstheater Schwerin" ) is the principal theatre of Schwerin in Germany.  Its main theatre (or "Grosses Haus") seats 650 people and is used for the performance of plays, opera, musical theatre and ballet.  Designed by Georg Daniel, it was built between 1883 and 1886 after the previous theatre had been destroyed by fire in 1882.  The theatre was inaugurated on 3 October 1886 with a performance of Gluck's "Iphigénie en Aulide" with Marie Wittich in the title role.  The complex also includes the State Museum in Schwerin ("Staatliche Museum Schwerin") and a 240-seat concert hall, now used for performances of chamber works.  All theatres were closed for the Autumn season of 1944, with the staff drafted wherever possible.  By German WW2 standards wartime casualties and destruction by bombing in Schwerin were small, in spite of nightly RAF raids and the droning of massive bomber pulks as silver specks on the sky during the day on their way to Berlin.  Americans were the first to enter the town in the spring of 1945, handing it over to the British until the Russians arrived.  These ordered the immediate reopening of the theatre, taking great interest in light operas and operettas as an art they very much appreciated, but until then out of their reach in most parts of Stalin's Soviet Union.  Not familiar with Central European culture, one saw their well-fed ladies wearing night gowns during the invariably full houses as a substitute for an evening dress.  In the immediate years to follow, there was a gradual exodus of key staff to the West, where few found equivalent employment.  The ensuing vacancies provided new chances for many musicians, who were prepared to stay in East Germany to gain important positions there in their later career. Magdaléna Hajóssyová (born 25 July 1946, Bratislava) is a classical Slovak soprano who has had an active international career singing in operas, concerts, and recitals since the late 1960s.  She has been particularly active at the Prague State Opera where she has been a principal artist since 1972.  She has also had a long and fruitful partnership with the Berlin State Opera beginning in 1975.  In 1977, 1981, and 1987, she won the Berlin Critic's Prize for her portrayal of the roles of Margarete in Charles Gounod's "Faust", the Elektra in Mozart's "Idomeneo", Carl Maria von Weber's "Euryanthe", and Christoph Willibald Gluck's "Iphigénie en Aulide". Iphigénie en Aulide ("Iphigeneia in Aulis") is an opera in three acts by Christoph Willibald Gluck, the first work he wrote for the Paris stage.  The libretto was written by François-Louis Gand Le Bland Du Roullet and was based on Jean Racine's tragedy "Iphigénie".  It was premiered on 19 April 1774 by the Paris Opéra in the second Salle du Palais-Royal and revived in a slightly revised version the following year. Robin Guarino (born April 3, 1960) is an opera and film director.  She has directed operas such as "The Marriage of Figaro", "Don Giovanni", "Lohengrin", "Così fan tutte" , and "The Magic Flute" at the Metropolitan Opera.  Also, she has directed at Seattle Opera, Glimmerglass Opera, Chautauqua Opera, Virginia Opera, and Wolf Trap Opera.  She continues to direct, most recently "L'etoile" and "The Marriage of Figaro" for the Wolf Trap Opera Festival, " La Calisto", "The Magic Flute" and "Iphigénie en Aulide" for Juilliard Opera Center, and at Gotham Chamber Opera, "Il Signor Bruschino".  She currently holds the J. Ralph Corbett Distinguished Chair in Opera at the University of Cincinnati College-Conservatory of Music." Iphigénie en Tauride ("Iphigeneia in Tauris") is a tragédie lyrique in four acts by Niccolò Piccinni, which was first performed on 23 January 1781 by the Académie royale de musique (the Paris Opéra) in the second Salle du Palais-Royal.  The opera's libretto, by Alphonse du Congé Dubreuil, is based on a play of the same name by Claude Guimond de La Touche, although the ultimate source was the tragedy "Iphigeneia in Tauris" by Euripides.
Answer: Iphigénie en Aulide