MacMillan studied at Edinburgh University and then with John Casken at Durham University. In 1990 he became affiliate composer of the Scottish Chamber Orchestra; he has since become visiting composer for the Philharmonia and artistic director of its Contemporary Music Series. His music is noted for its energy and emotional power, its religious and political content and its references to Scottish folk music. Major works include The Beserking (1990), a piano concerto for Peter Donohoe; Sinfonietta (1991); and Veni, veni, Emmanuel (1992), Symphony No 2 (1991) and Symphony No 3 (2002). His 50th birthday saw concerts at the BBC Proms and the Edinburgh Festival, and 2010 saw the US premiere of his St John Passion (2008) under Sir Colin Davis. Recent works include a Violin Concerto (2010) for Vadim Repin and a Third Piano Concerto for Jean-Yves Thibaudet (2011).