Derek Strahan was born in Penang, Malaysia on May 28th 1935, and spent his early childhood in colonial Malaysia. He was evacuated with his mother and sister to Perth when Singapore fell to the Japanese in February 1942. In 1946 the Strahans settled in Northern Ireland and Derek completed his schooling in Belfast, coming into conflict with authority and community mores due both to his interest in music and his desire to become a composer and to his developing radical views on religion and politics (derived from the writings of George Bernard Shaw).

At Cambridge University, Strahan enrolled in an Arts degree in modern languages (French and Spanish). He developed an interest in theatre and cinema, and acted in a number of university productions. His musical activities were restricted to playing the piano for pleasure and teaching himself the guitar. He graduated in 1954 and worked in London for the next six years as relief teacher, actor, singer-songwriter and Assistant Film Director making commercials.

In 1961 Strahan returned to Australia and settled in Sydney. He combined composing film music and performances as singer/songwriter with work as film director, scriptwriter, actor and teacher. From 1980, he resolved to give greater importance to composing, and increased his output of works for concert performance. However, he maintained contacts in the Australian film industry, and has been involved in the production of three Australian feature films for which he has written script and music, and two of which he has co-directed. He has composed music for over thirty films documentaries, and has written over twenty concert music works encompassing solo, ensemble, vocal and orchestral pieces. Much of his film and concert music has been released on the Australian Jade and Revolve label.s, and, since 1982, has been consistently broadcast on national radio.

Essentially self-taught as a composer, Derek Strahan’s music is melodic, making use of polyphony and polymetrics, and has attracted performance by distinguished artists. Mezzo-soprano Lauris Elms AM OBE commissioned Strahan’s song cycle "Rose of the Bay", premiering the work at the Sydney Opera House in 1987, and recording it for the ABC and for CD release. Two works written for cellist Georg Pederson — "China Spring" and Solo Cello Suite No. 1 — have also been recorded by the ABC.

Strahan has received a number of commissions for his music, including the commission of Piano Trio No. 1 in F for the 1988 Bicentennial celebrations. This work was premiered on Australia Day 1988 at a champagne breakfast in Sydney’s Centrepoint Tower. Canberra School of Music commissioned "Voodoo Fire" for clarinet, percussion and synthesiser (1996), and Clarinet Concerto (2002). Michael Scott commissioned the flute and piano work "Atlantis" which develops material for Strahan’s "Atlantis" opera project, as does “Eden In Atlantis”, a 25-minute Scena for soprano, flute and piano, premiered in 1996 at the Joan Sutherland Room, Opera Centre, by Liza Rintel, Michael Scott and David Miller AM.