Garrett has had an extensive music career. A graduate of the Royal Academy of Music and an alumna of the prestigious National Opera Studio, she won the Decca Prize of the Kathleen Ferrier Award in 1979, thereby launching her career. Her professional debut, in 1979, was as Amor in "Orontea" at the music festival in Batignano. She subsequently sang, in 1980, Alice in "Le comte Ory" at the London Coliseum and Dorinda in "Orlando" at the Wexford Festival, in 1981, also at Wexford, the title role in "Zaide", in 1982 Sophie in "Werther" with Opera North and in 1984 Damigella in "L'incoronazione di Poppea" at Glyndebourne. From 1984, as principal soprano at English National Opera, she became well known for her performances in productions of the operas "Serse", "Le Nozze di Figaro", "Così fan tutte", "Die Fledermaus" and "The Mikado".