MacKenzie Theory was an Australian jazz rock group formed in September 1971 in Melbourne. Lead guitarist, Rob MacKenzie, and electric viola player, Cleis Pearce were the mainstays. They recorded two albums, Out of the Blue (1973) and Bon Voyage (1974) for Mushroom Records before disbanding in May 1974. Out of the Blue peaked at No. 19 on Go-Set‍‍ '​‍s Australian Albums chart. In the 1990s, MacKenzie was a member of United States rock'n'roll revival act, Sha Na Na.