From a press release on May 17, 2012.
Gwyn Hughes-Jones will make his Met role debut as Manrico in Il Trovatore on September 29 and sings the role on October 4, 8, 12, 17, 20, and 25.
Carmen Giannattasio will replace Sondra Radvanovsky as Leonora in Il Trovatore on October 12, 17, 20, and 25. These performances are in addition to the previously announced dates when Giannattasio will sing the role.
Sondra Radvanovsky will replace Karita Mattila as Amelia in Un Ballo in Maschera on November 8 through December 8. The role of Amelia for the performance of December 14 is to be announced.
Marcelo Álvarez will sing Gustavo III in Un Ballo in Maschera on November 27, replacing Roberto De Biasio. Álvarez will now sing all performances of the role in the 2012-13 season.
Dolora Zajick will replace Olga Borodina as Amneris in Aida on December 19, 22, and 28. As previously announced, Borodina will sing the role on November 23, 26, 29 and December 3, 7, 12, and 15.
Erwin Schrott will make his Met role debut as Dulcamara in Bartlett Sher's new production of L'Elisir d'Amore on January 30. He will also sing the role on February 2, 6, and 9 matinee.
Sondra Radvanovsky will not be singing any performances of Don Carlo in the 2012-13 season, and her replacement as Elisabeth de Valois is to be announced.
Italian baritone Marco Vratogna will make his Met debut as Iago in Otello on March 27. He replaces Thomas Hampson, who will still sing the performances on March 11, 15, 20, 23, and 30.