It was during the Kyser band's appearance in Carolina Blues (1944) that Duning's work was noticed, leading to a contract with Columbia Pictures.
Morris Stoloff signed Duning to Columbia Pictures in 1946, where he worked almost exclusively through the early 1960s, collaborating most often with director Richard Quine.
Prominent Duning scores are two of the best examples of western genre – the original 3:10 to Yuma, and Cowboy – and those he composed for films as diverse as Picnic, The World of Suzie Wong, The Devil at Four O'Clock, Bell, Book and Candle, and Toys in the Attic.
His notable television work includes Tightrope, Star Trek, The Big Valley, and Naked City, as well as TV miniseries such as Top of the Hill (1980), The Dream Merchants (1980), and Goliath Awaits (1981).
He also served on the board of the Academy of Motion Picture Arts and Sciences, and was active in numerous other music industry organizations.