Although Addison was offered more opera roles with several companies, she did not appear in many more opera productions as she preferred to sing in recital and on the concert stage. She did appear in a few more productions with the New York City Opera and the New England Opera Theatre. Her other opera roles included the title role in Handel's Acis and Galatea, Gilda in Verdi's Rigoletto, Micaela in Bizet's Carmen, Fiordiligi in Mozart's Cosi fan tutte, and Nannetta in Verdi's Falstaff among others. In 1959, Addison sang the role of Bess in the film version of Gershwin's Porgy and Bess. The role was initially supposed to be sung by Urylee Leonardos, but apparently Leonardos' voice sounded too shrill when recorded so they replaced her with Addison at the last minute. In a 1996 Opera News interview she said, "Today, young singers are almost forced to make a choice, because they are counseled that becoming established in opera is the way to make a career in music. I never had to make a choice. I loved the song repertoire from the start, and as I began to sing, for even the smallest ladies' clubs, etc., those inviting me expected and accepted that.... Even as the years passed, and I sang all the rest of the repertoire -- opera, oratorio, chamber music, etc. -- the first love remained.... My curiosity, joy and love for song never changed. It still has not."
Addison made numerous appearances with major orchestras, such as the Boston Symphony Orchestra, the Hollywood Bowl Orchestra, and the Cleveland Orchestra. In 1959 she was chosen by Leonard Bernstein as the soprano soloist in the American premiere of Francis Poulenc's Gloria. She became a favorite of Bernstein and the two collaborated frequently, including on a number of recordings. In 1961 he invited her to sing the soprano solos in the world premiere of Lukas Foss' Time Cycle' with the New York Philharmonic. She performed the work again later that year with Izler Solomon and the Indianapolis Symphony Orchestra. She also sang under Bernstein for the opening of Lincoln Center's Philharmonica Hall (now Avery Fisher Hall).
Other noted performances by Addison include the world premiere of Lester Trimble's Canterbury Tales and her interpretation of Debussy's L'Enfant Prodigue. Towards the late 1960s, Addison's performing career began to slow down as she focused more on teaching. Although retired now, she taught voice on the collegiate level for more than thirtyfive years. She has been a voice teacher for SUNY at Stony Brook, Eastman School of Music and Aspen Music Festival and School. For many years, she was also on the faculty, serving for a time as Chair, of the Voice Department at the Manhattan School of Music, which awarded her an honorary doctorate in 2001. Many of her students, such as Dawn Upshaw, have gone on to have successful careers. Addison once said,"What I try to pass on to my own students at the Manhattan School of Music is to make them aware of their own abilities, to know how much they need to know in order to be a singing musician."