Anton Haizinger heard Haizinger sing in concerts, and offered him an engagement at the theatre; Haizinger gave up teaching. Haizinger's first roles at Theater an der Wien, in 1821, were in two operas by Rossini, as Gianetto in "La gazza ladra" and Lindoro in "L'italiana in Algeri". He soon became well-known in Vienna. The role of Adolar in Weber's opera "Euryanthe", premiered in 1823 at the Theater am Kärntnertor, was created for him, and he was a soloist in the premiere in 1824 of Beethoven's Ninth Symphony at the same theatre. He continued studies with Antonio Salieri. At this time, Italian opera
La Scala backlash caused serious disruptions and staff strikes. In a statement, the theatre's board said it was "urgent to unify the theatre's management." On 16 March 2005, the La Scala orchestra and other staff overwhelmingly approved a no-confidence motion against Muti, and demanded the resignation of Fontana's replacement, Mauro Meli. Muti had already been forced to cancel a concert a few days earlier because of the disagreements. Italy's culture minister, Giuliano Urbani, supported the conductor but called for urgent action by management to safeguard the smooth operation and prestige of La Scala. On 2 April 2005, Muti resigned from La Scala,