Norwegian music composer who served as the first director of the Norwegian Concert Institute and was considered a neoclassicist and expressionistic.
His first composition to be played in public was his Trio for Strings, Opus 3, which debuted at the Young Nordic Music Festival in 1950.
He taught composition at the Oslo Conservatory of Music beginning in 1973.
He was the son of an Oslo publisher named Ernst Gustav Mortensen.
He was less famous than fellow Norwegian composer Edvard Grieg.