Moss was born and raised in Los Angeles. He grew up surrounded by the theatre, concert, and rock & roll music world. At age 11, he started learning to play the drums, guitar and electric bass. In 1976, Moss joined creative forces with fellow singer/guitarist Peter Beckett, guitarist/keyboardist J. C Crowley, and drummer John Friesen to form the band Player, primarily as bassist and singer. In a garage in the Hollywood Hills, they wrote and rehearsed the music that would soon attract the attention of music impresario Robert Stigwood, who signed them to his RSO Records.