1961 Duncan was voted best young violinist in Great Britain at the age of 11, after which he successfully gained a music scholarship to Shrewsbury Public School.
In 1967 he completed his academic studies in music and obtained both L.T.C.L. and L.R.S.M diplomas in violin.
In 1970 Duncan was invited to tour Brazil with members of the Sergio Mendes Band, after which he toured throughout South Africa and Rhodesia. (Later to become Zimbabwe) . During this time, he composed and recorded Chimera, his first solo album in South Africa.
Duncan established a progressive music venue in Jeppe Street, Johannesburg, called the Branch Office. It was here that he established his unique multi-keyboard technique. In 1973, he was heard by A&R man, Peter Knight Jnr. of Phonogram Records and invited to travel back to the United Kingdom to join up with Ginger Bakers new band. He moved on to team up with Gary Moore and Jon Hisemans band Coliseum 2.
In 1975, he joined Steve Harley & Cockney Rebel. Come Up And See Me, Make Me Smile went to No1 in the UK and Europe. This was followed by extensive touring and a further 4 gold albums. During this time Duncan released his 2nd solo album Score published by EMI Records. This album has become a collectors item in recent years.
Duncan did much session work during this time, at the famous Abbey Road Studios. He played, on the first 3 Kate Bush albums one being "The Kick Inside" which included the hit "Wuthering Heights", three Alan Parsons Projects (Producer of Dark Side of The Moon), "I, Robot" (1977 Arista); "Pyramid" (1978 Arista) "Eve" (1979 Arista) and with rock groups such as Camel and Budgie. In 1978 he composed and released his 3rd solo album VISA.
1979 and he moved on to become a member of the British supergroup, 10cc. Their hit Dreadlock Holiday from the "Bloody Tourists" album went to No1 worldwide and achieved 3 Gold and Platinum albums. During this time Duncan ventured into the film score arena and co-composed the soundtrack for the French movie, Girls with Eric Stuart. 1983 saw Duncan taking up the post as Musical Director for Elkie Brooks. He co-composed and played keyboards on 3 of her albums.
1990 Four years of work on a joint project with Richard Hill came to fruition with a performance and recording in East Berlin of Orchestral Evolution, a symphony for synthesizers and a 90-piece orchestra. This featured soloists from the Chris Barber Jazz Band. In the same year, Duncan teamed up with Neil Lockwood, (later to be lead singer with ELO 2) to co-write and produce the Lockwood/Mackay Album.
Later that same year, he composed and produced another solo album A Picture of Sound.
In 1993 Duncan moved to Cape Town, South Africa, working extensively in the visual media, composing the soundtrack for The Syndicate, SABCs highly rated 13-part drama series.
In 2003, Duncan teamed up with long-time friend, singer/songwriter and guitarist Greg McEwan, to form REUNION, co-writing, producing, and arranging The First Time their debut album. Duncans instrument of notoriety and choice being the Hammond B3, features prominently amongst the keyboards on the album. RÉUNION are in the initial stages of preparation for the Planet Lion Earth Tour.