Question: Which opera premiered first, La clemenza di Tito or Idomeneo?
Context: Idomeneo, re di Creta ossia Ilia e Idamante (Italian for "Idomeneus, King of Crete, or, Ilia and Idamante"; usually referred to simply as Idomeneo, K. 366) is an Italian language opera seria by Wolfgang Amadeus Mozart.  The libretto was adapted by Giambattista Varesco from a French text by Antoine Danchet, which had been set to music by André Campra as "Idoménée" in 1712.  Mozart and Varesco were commissioned in 1780 by Karl Theodor, Elector of Bavaria for a court carnival.  He probably chose the subject, though it might have been Mozart.  The work premiered on 29 January 1781 at the Cuvilliés Theatre in Munich, Germany. Annemarie Kremer, Emmer Compascuum, June 2, 1974, is a Dutch operatic soprano, known for her performances in the title roles of "Norma", "Tosca", and "Salome" and as Vitellia in "La clemenza di Tito".  She has appeared at a variety of European opera houses including the Opernhaus Dortmund, the Staatsoper Stuttgart, and Opera North in England. Luise Willer (1888–1970) was a German operatic contralto.  She made her professional opera debut in 1910 as Annius in Wolfgang Amadeus Mozart's "La clemenza di Tito".  She spent most of her career performing at the Bavarian State Opera in Munich.  At the Bayreuth Festival, she portrayed Brängane in "Tristan und Isolde".  She created roles in several world premieres during her career, including Barbara in Erich Wolfgang Korngold's "Violanta" (1916), Lukrezia in Hans Pfitzner's "Palestrina" (1917), Graben-Liese in Franz Schreker's "Das Spielwerk" (1920), and Herzogin in Pfitzner's "Das Herz" (1931) among others. Heidi Brunner (born 1966) is a Swiss opera singer.  She began her career as a mezzo-soprano at the Anhaltisches Theater in Dessau in 1993.  After making appearances at the opera houses in Basel, Innsbruck, and Biel, she was a member of both the Vienna State Opera and Vienna Volksoper from 1996 to 1999.  Among the roles she sang in Vienna were Adalgisa in "Norma", Annio in "La clemenza di Tito", and the title role in "La Cenerentola".  She then sang as a guest artist with theatres throughout Europe, including making appearances at the Bavarian State Opera, the Grand Théâtre de Genève, the Komische Oper Berlin, the Liceu, and the Salzburg Festival.  In the 2004-2005 season she began performing roles from the soprano repertoire, beginning with a performance of Franz Schreker's "Irrelohe". The Stresa Festival Orchestra is a formation composed by young and talented musicians, coming from renewed european orchestras, calling by Gianandrea Noseda to perform every year some original production for the Stresa Festival.  The debut of the Orchestra, on 26 August 2003 with Mozart’ "Don Giovanni", began the project of the concert performances of different operas: "Così fan tutte" (2004), "Le nozze di Figaro" (2005), "The magic flute" (2006), "La clemenza di Tito" (2007), "The Rake’s progress" (2008), "La Cenerentola" (2009), "Idomeneo" (2010).  During the years many singers was invited such as Evgenij Akimov, Simone Alberghini, Sergej Alexashkin, Tatiana Borodina, Nicola Beller Carbone, Natale De Carolis, Mariella Devia, Barbara Frittoli, Vivica Genaux, Massimo Giordano, Andrew Kennedy, Alessandra Marianelli, Peter Mattei, Sally Matthews, Francesco Meli, Maxim Mironov, Tomislav Muzek, Laura Polverelli, Nicola Ulivieri, Franco Vassallo. Glenn Winslade (born 1958) is an Australian operatic tenor known for his interpretations of dramatic roles such as Florestan in "Fidelio", the title role in "Idomeneo", the title role in "La clemenza di Tito", Erik in "The Flying Dutchman", the title role in "Rienzi", the title role in "Lohengrin", the title role in "Tannhäuser", the Emperor in "Die Frau ohne Schatten", Apollo in "Daphne", Bacchus in "Ariadne auf Naxos" and Max in "Der Freischütz". La clemenza di Tito ("The Clemency of Titus") is an 18th-century Italian opera in 3 acts by the Czech composer Josef Mysliveček.  It was composed to a libretto by the Italian poet Metastasio that was first performed in 1734 with music of Antonio Caldara.  For a performance in the 1770s, it would only be expected that a libretto of such age would be abbreviated and altered to suit contemporary operatic taste (similar to the setting of the same text by Wolfgang Amadeus Mozart).  The cuts and changes in the text made for the 1774 performance of Mysliveček's opera are not attributable.  All of Mysliveček's operas are of the serious type in Italian language referred to as opera seria. Adam Plachetka (born 1985) is a Czech bass-baritone.  He was born in Prague, where he was also educated, and won several singing competitions in the Czech Republic.  In 2005 he made his debut at the National Theatre in Prague, where his roles have included the title role in "Don Giovanni", Figaro ("Le nozze di Figaro"), Guglielmo ("Così fan tutte"), Nardo ("La finta giardiniera"), Publio ("La clemenza di Tito") and Argante ("Rinaldo").  For the Prague State Opera, he sang Papageno ("Die Zauberflöte") and Don Basilio ("Il barbiere di Siviglia"). La clemenza di Tito ("The Clemency of Titus") is an opera by the composer Christoph Willibald Gluck.  It takes the form of a "dramma per musica" in three acts.  The Italian-language libretto is by Pietro Metastasio.  The opera premiered on 4 November 1752 at the Teatro San Carlo in Naples. La clemenza di Tito (English: "The Clemency of Titus"), K. 621, is an "opera seria" in two acts composed by Wolfgang Amadeus Mozart to an Italian libretto by Caterino Mazzolà, after Metastasio.  It was started after the bulk of "Die Zauberflöte " ("The Magic Flute"), the last opera that Mozart worked on, was already written.  The work premiered on 6 September 1791 at the Estates Theatre in Prague.
Answer: Idomeneo