By 1966 Douglas was established as one of Melbourne's most sought-after Baritone soloists, and he was appointed as a Principal with the National Theatre Opera Company where his roles included the title roles in Rigoletto, The Marriage of Figaro and Marcello in Puccini's La Bohème.

Now well known to many through his conducting of the Hallelujah chorus at GTV 9's national broadcast of Carols by Candlelight, Douglas has had many years involvement in the community of Melbourne as an orchestral and choral conductor.

Founder of the Camerata Orchestra in 1976 and conductor of the Camberwell Chorale since 1974, his repertoire includes works of Bach, Beethoven, Bloch, Elgar, Hovhaness, Mozart, Schubert, Tippet, Vaughan Williams and Verdi. He has also premiered compositions by Melbourne composers Michael Easton and Stelios Tsiolas.

He was awarded an OAM for his services to community music and music education.

Douglas maintains a long-standing association with the Victorian College of the Arts Opera Course as lecturer in Stagecraft and Drama.