Marty was brought up in Australia, originally training to be an architect at Melbourne University. In 1969 he became a member of the original line up of the New Seekers, along with Chris Barrington, Eve Graham, Sally Graham and Laurie Heath. He wrote or co-wrote many of the New Seekers' songs. He left the group in April 2002.
He is married with two sons: Jamie (born 1981) and Oliver (born 1982).