During 1939 to 1942, the last prolific period near the end of her compositional career, her style became more clear and contrapuntal, with emphasis on motivic elements and tonal structures, the hallmarks of neoclassicism. "Dumka" (1941), a recently published work for violin, viola, and piano, reflects the Eastern European folk styles of Bartók and Martinů. The "Passacaglia on an Old English Tune", also from 1941 and premiered by Clarke herself, is based on a theme attributed to Thomas Tallis which appears throughout the work. The piece is modal in flavor, mainly in the Dorian mode but venturing into the seldom-heard Phrygian mode. The piece is dedicated to "BB", ostensibly Clarke's niece Magdalen; scholars speculate that the dedication is more likely referring to Benjamin Britten, who organised a concert commemorating the death of Clarke's friend and major influence Frank Bridge. The "Prelude, Allegro, and Pastorale", also composed in 1941, is another neoclassically-influenced piece, written for clarinet and viola (originally for her brother and sister-in-law).