A singer with an unusually broad repertoire that encompassed both classical and contemporary works, she notably created roles in the world premieres of operas by composers Dominick Argento, David Carlson, Carlisle Floyd, Gian Carlo Menotti, Thomas Pasatieri, and Ned Rorem.
She returned frequently to the SFO during her career, portraying such roles as Baba the Turk in The Rake's Progress, Countess Geschwitz in Lulu, Herodias in Salome, La chatte in L'enfant et les sortilèges, Marcellina in The Marriage of Figaro, Mark Smeaton in Gaetano Donizetti's Anna Bolena, The Mother in Mavra, the Old Woman in Yerma, Prince Orlofsky in Die Fledermaus, Saint Catherine in Jeanne d'Arc au bûcher, Tisbe in La Cenerentola, Zita in Gianni Schicchi, and the title roles in Carmen and Regina.
[11] Other roles she performed with the WNO during her career included Agata in Maria Golovin,[12] The Old Baroness in Samuel Barber's Vanessa[13] Seibel in Faust,[14] and Ursule in Béatrice et Bénédict.
[15] In 1986 she appeared at the WNO as Queen Isabella of Spain in Christopher Columbus, a pastiche of music by Jacques Offenbach patched together by Patric Schmid.
[17] In 1965 Bonazzi created the role of Christine in the world premiere of Ned Rorem's Miss Julie for her debut with the New York City Opera (NYCO).
[18] She sang several more roles with the NYCO, including Clairon in Capriccio,[19] Frau von Luber in Der Silbersee,[3] Katisha in The Mikado,[20] Mme.
[30] In 1972 she created the title role in the world premiere of Thomas Pasatieri's Emmy Award-winning opera, The Trial of Mary Lincoln which was commissioned by the National Educational Television network under the leadership of Peter Herman Adler.
[34] Bonazzi appeared in numerous rarely seen operas with the Clarion Music Society at Alice Tully Hall during the 1970s and 1980s, including Anfione in Agostino Steffani's Niobe, regina di Tebe, Apollo in Francesco Cavalli's Giasone, Baroness Aspasia in Gioachino Rossini's La pietra del paragone, Juno in Gluck's Le nozze d'Ercole e d'Ebe, and Lavinia in Steffani's Amor vien dal destino.
[41] In 1993 she created the role of Lady Neville in the world premiere of David Carlson's The Midnight Angel at the Opera Theatre of Saint Louis.