In the 1930s Jacob, along with several other young composers, wrote for the Sadler's Wells Ballet Company (now The Royal Ballet). His one original ballet (other than a student work, "The Jew in the Bush" (1928)), was "Uncle Remus" (1934), written for them. During the Second World War, Jacob wrote music for several propaganda films, and after the war he provided the score for the feature film "Esther Waters" (1948). A more personal take on the war is evident in the austere "Symphony for Strings" (1943), written for the Boyd Neel Orchestra.