Formed a folk/rock band, Second Timothy while attending college in Florida. In 1972, Duncan moved to California and formed Sweet Comfort (later renamed as [a=The Sweet Comfort Band].) He would remain with them until they first disbanded in 1984. Duncan began to perform solo after that.
Duncan leads Radio Rehab, a charity he created to support recovery programs. Radio Rehab programs are available online and on several radio networks, including the Armed Forces Radio Network.