While her performance credits included leading roles at most of the world's major opera houses, she never achieved a high level of international fame.

She did not participate in any commercial audio recordings, although her voice is preserved on a few television and radio broadcasts made in Germany, Canada, and the United States.

Born Alma Claire Williams, Barlow worked as a secretary, salesperson, receptionist and model before pursuing an opera career.

She studied voice under Cecile Jacobson in New York City and made her professional recital debut as a coloratura soprano at Carnegie Hall in 1954.

[4] Barlow's first major success came in 1966 when she made her debut at the Komische Oper Berlin as Donna Anna in Wolfgang Amadeus Mozart's Don Giovanni.

[7] Time stated that, "To New York audiences who have seen almost nothing for 15 years except Birgit Nilsson's cool, ruminative portrayal, Barlow's sexy Isolde came as a pleasant shock.

Barlow returned to the Met several more times during the 1970s, singing Marina in Boris Godunov (1975), Amelia in Un Ballo in Maschera (1975-1976), and the title role in Elektra (1975).

[9] That same year she sang Donna Anna to Jerome Hines's Don Giovanni for her debut with the Philadelphia Lyric Opera Company.

[2] In 1974 she made her debut at La Scala as Fata Morgana in Sergei Prokofiev's The Love for Three Oranges, also singing Leonore in Fidelio with the company that year.

After comparing her versatility to that of soprano Florence Easton, Porter noted that "there is not much sensuous allure in Barlow's firm, strong tone, and no trace of dainty charm in her heroic manner.

Some of her other opera roles included Abigaille in Nabucco, Agathe in Der Freischütz, Elisabetta in Don Carlos, Elsa in Lohengrin, Giulietta in The Tales of Hoffmann, Minnie Falconer in La fanciulla del West, Senta in The Flying Dutchman, and the title roles in Arabella, Ariadne auf Naxos, Jenůfa, Norma, Salome, Tosca, and Turandot.