In 1975, Bartoletti became sole artistic director, and held the post until his retirement in 1999. Following his retirement, he had the title of artistic director emeritus for the remainder of his life. Bartoletti began as Lyric Opera's principal conductor in 1964, and served in that capacity until 1999. Over the period from 1956 to 2007, Bartoletti conducted approximately 600 performances of 55 operas with Lyric Opera, with his final conducting appearance at Lyric Opera in a 2007 production of "La traviata". His other notable conducting work at Lyric Opera included conducting the US premiere of Britten's "Billy Budd" in 1970, and the 1978 world premiere of Krzysztof Penderecki's "Paradise Lost". Bartoletti focused almost exclusively on opera in his career, with few conducting engagements in symphonic work. He conducted several world premieres of works by composers such as Luciano Berio, Luigi Dallapiccola, Paul Dessau, Lodovico Rocca, Gian Francesco Malipiero, and Alberto Ginastera ("Don Rodrigo", 1964). His commercial recordings Ponchielli's "La Gioconda", Puccini's "Manon Lescaut", and "La Cena delle Beffe" of Umberto Giordano (from the Opernhaus, Zürich, in 1996), as well as DVDs of "Death in Venice", "La bohème", "Giovanna d’Arco", "Macbeth", "La gazza ladra", and television films of "La sonnambula" and "Tosca". The Italian government had bestowed on Bartoletti the rank of "Cavaliere di Gran Croce della Repubblica Italiana". He was also a member of the Accademia di Santa Cecilia, and a winner of the Abbiati Prize. In his later years, Bartoletti taught at the Accademia Chigiana in Siena. His final operatic performance was a production of "Manon Lescaut" in February 2011. Bartoletti was married to the former Rosanna Sandretti, an elementary-school teacher, from 1 July 1953 until her death on 2 August 2011. The marriage produced two daughters, Chiara Bartoletti and Maria Poggi, who both survive Bartoletti. Other survivors include a sister, a brother, and five grandchildren, Livia, Filippo, Arianna, Margherita, and Nicolò.