Ursula emigrated alone to New York City in 1940 to attend the Mannes School of Music, which had offered her full scholarship on the basis of one of her compositions.
Other teachers include Roger Sessions and Ralph Shapey in composition and Eduard Steuermann, one of the foremost piano pedagogues at the time, in performance.
Though Hindemith was one of her earliest influences, Mamlok credited the works of serial composers, including Schoenberg, Berg and Webern, as having the greatest impact on her compositional style.
"[citation needed] Mamlok composed extensively for small chamber ensembles of various configurations as well as works for piano.
In 1984, When Summer Sang, a chamber work for flute, clarinet, violin, cello and piano, was chosen to represent the United States at the International Rostrum of Composers.