Fraser co-wrote Free's biggest hit 'All Right Now' in 1970. He co-founded the band at the age of 15 in 1968 with Paul Kossoff, Paul Rodgers and Simon Kirke.
In 1972, Fraser left Free to work with guitarist Chris Spedding on the Sharks, before forming his own group the Andy Fraser Band.
Over the years, the Paddington-born songwriter has penned tracks for artists including Robert Palmer, Joe Cocker and Rod Stewart.
The exact cause of death is not yet clear, although Fraser was battling both cancer and HIV.