Cotter also wrote the music for Merlinda Bobis' radio play "Rita's Lullaby", which won the Prix Italia in 1998.
He moved to Canberra in the late 1960s with his family and continued performing in this tradition but gradually drifted towards more modern forms of jazz and rock and roll.
He performed with the Canberra bands, The Bitter Lemons, The Firing Squad, Family Portrait as well as in more experimental collectives with musicians Colin Hoorweg, Dave Kain, Mitch Burns, Christian Wojtowicz and John Tucker.
[4] An Australia Council Young Composers Fellowship enabled him to discontinue his formal studies and take up the position of Music Director at Canberra Repertory Society, pursuing a more practical approach to compositional activities with the full support of his mentors.
[5] His students have included Marian Budos,[6] Michael Sollis,[7] Kate Moore,[8] and Tim Hansen.