Morthenson (born April 7, 1940 in Örnsköldsvik, Sweden) is a prominent Swedish composer, critic, and writer primarily known for his criticism of music in Sweden and his compositional styles of non-figurative music, music that aimed to avoid any relationship to past compositional techniques, and meta-music, which alluded to historical music genres in order to criticize them.
Morthenson's success as a composer and intellect in Sweden is reflected by the influential positions he has held throughout his career.
He was on the board for the Electronic Music Studio from 1973-1975, he acted as chairman of the Swedish section of the International Society for Contemporary Music (ICSM) from 1974-1975, he was vice-chairman of the ISCM council from 1975-1978, and he was also the chairman for Fylkingen, a Swedish chamber music society that focuses primarily on new music, from 1975-1976.