...not the one you're probably thinking of. This Brian May wrote soundtracks in Australian film. He was an accomplished composer who was active when the Australian film industry rose to prominence in the 1970s and 1980s. If it's an Ozploitation classic, chances are that Brian May wrote its music.
May trained at Adelaide's Elder Conservatorium and worked for a number of years as a conductor and musical director for the Australian Broadcasting Commission. He entered film scoring in 1975 with the soundtrack for The True Story of Eskimo Nell. More than 30 other soundtracks followed. Although he continued to work in Australia, May spent part of the 1990s in Hollywood. He suffered a fatal heart attack in 1997.
May's influences include Alban Berg, Bela Bartók, Igor Stravinsky, Krzystof Penderecki and Bernard Herrmann. He was skilled at creating tense atmospheres and feelings of unease. This was often accomplished by using staccato, percussive string arrangements in the vein of Herrmann's score for Psycho, though he also used brass and synthesizers. Australian film budgets did not allow for full orchestras, but May made effective use of smaller ensembles with unusual instrumentations. Mad Max creates a jagged feel by using a large percussion section and brass instruments played outside of their normal range.
May is considered to have introduced modernist compositional techniques to Australian film scoring, and he was the first to write original theme music for Australian television shows. He won the 1979 Australian Film Institute Best Original Score award for the Mad Max soundtrack. New York University awards a scholarship in his honor.