English conductor, composer, and horn player. He founded the Chelsea Symphony Orchestra in 1944, and was a guest conductor with leading orchestras. He conducted an enormously wide range of music, but was especially known for Mahler, Elgar, and other late Romantics, above all Strauss, and was noted for his clear interpretations of complex scores. He also composed two symphonies, a string quartet, and a number of horn pieces.
He wrote three volumes on Richard Strauss (1960–72), as well as Orchestral Variations (1981) and Companion to the Orchestra (1987).
Career Del Mar was born in London and was educated at Marlborough public school. At the Royal College of Music, London, he studied violin, piano, and horn; conducting with Constant Lambert; and composition with Reginald Morris and Ralph Vaughan Williams. In World War II he played the horn in the RAF Central Band.
With the Chelsea Symphony Orchestra he performed what were then little-known modern works such as Mahler's Second and Ninth Symphonies. He became Thomas Beecham's assistant with the Royal Philharmonic Orchestra in 1947, conducting Strauss in the composer's presence. He was principal conductor of the English Opera Group 1949–56, and met Benjamin Britten and conducted his Let's Make an Opera and The Rape of Lucretia at the Aldeburgh Festival in 1949.
He was appointed chief conductor of several orchestras (including the British Broadcasting Corporation (BBC) Scottish Orchestra in 1960, the Göteborg Symphony Orchestra, Sweden, in 1968, the Academy of the BBC 1974–77, and the Århus Symphony Orchestra, Denmark, 1985–88) but not of any of the major London orchestras. He was also a professor of conducting at the Guildhall School of Music 1953–60 and the Royal Academy of Music 1974–77.