John Frandsen studied at the Royal Academy of Music. He conducted the Danish National Radio Symphony Orchestra from 1945 to 1946 and was principal conductor at the Royal Danish Opera from 1946 to 1980. After that he returned to the Danish Radio as a conductor and musical adviser while retaining his connection with the Royal Theatre as a guest conductor. John Frandsen was one of the ourstanding Danish conductors of his time, not least as an interpreter of the Romantic repertoire but also of more recent opera and orchestral music. He was one of the leading specialists in the works of Carl Nielsen and received the prize of the Carl Nielsen Fund in 1981; he was also the first Danish conductor to introduce the music of Benjamin Britten to audiences in Denmark. He toured in the United States and most of Europe, made recordings of Danish music, and introduced new music in his capacity of conductor for The Young Composers' Association. John Frandsen managed the Opera Academy in Copenhagen from 1950 to 1980.