Easdale began his musical education at the Westminster Abbey Choir School before completing it at the Royal College in London between 1927 and 1933, where his principal teacher was Gordon Jacob
. There, at the precocious age of 18 he composed the first of three operas, Rapunzel, followed in 1935 by The Corn King (a "ritual" not staged until 1950 at Paddington), and The Sleeping Children in 1951 (a chamber opera with text by Tyrone Guthrie, produced in 1951 at Cheltenham). In 1929 his Dead March was played by Sir Malcolm Sargent
and the London Symphony Orchestra
, which gained the 20-year-old composer considerable attention. Despite Easdale's interest in the stage and, later on, film, he was recognized first for his orchestral music. Five Pieces were played at Vienna in 1936, and two years later a Piano Concerto was broadcast. In 1936 he also wrote Six Poems for small orchestra, and in 1939 a simply-titled Tone Poem. During this same prewar interval he also composed The Phoenix and Bengal River.
Easdale began scoring documentary films in 1937, which he continued to do during his WWII service with the Royal Artillery. In 1947, he began the 14-year association with the writer-director-producer team of Powell and Pressberger, who followed Black Narcissus and The Red Shoes with The Small Back Room (aka Hour of Glory), The Elusive Pimpernel (released stateside as The Fighting Pimpernel five years later), Gone to Earth (aka The Wild Heart), Outcast of the Islands, Gypsy Blood, The Green Scarf, The Pursuit of the Graf Spee (which had three different titles), Miracle in Soho, and Face of Fear (originally Peeping Tom), culminating in The Queen's Guards.
He wrote chamber music early on, plus an Evening Prelude for organ in 1951, a lyric drama entitled Seelkie in 1954 for chorus and chamber orchestra, and a Cavatina for Brass Ensemble in 1961. Along with Benjamin Britten
, he was commissioned to write music for the new Coventry Cathedral's consecration in 1962. The younger composer's War Requiem, however, cast Easdale's Missa coventriensis for choir, congregation, and organ into the shadows (from which it never seems to have emerged). In 1963, he returned to his Red Shoes music, fashioning a suite in four movements for concert orchestra. His last listed work, apart from the single return to film in 1978, was a song cycle based on excerpts from Leaves of Grass. A brief entry in The New Grove characterized Easdale's music as "mostly in an eclectic English idiom that owes something to [early] Britten
as well as the Bax-Bridge generation."