Since his 18th year Peter Hagen has been involved with choirs, singing firstly with the Melbourne Youth Choir under the direction of Faye Dumont. He subsequently gained further experience singing with numerous suburban choirs for carols services as a tenor mostly but sometimes as a bass and even alto. Later he sang in the St Paul’s summer choirs, the Canterbury Fellowship at Trinity College Melbourne, the Tudor Choristers and the Ormond College Chapel Choir.
Up to the early 1990s he directed various choirs, including at Lauriston Girls’ School as the Junior Music Coordinator. He was also a tutor at the Australian Children's Choir, and a teacher of keyboard skills through the Yamaha Music foundation.
Peter furthered his musical studies in baroque music and harpsichord in The Netherlands, where he also directed choir rehearsals in Amsterdam. Since returning to Australia he has organised numerous chamber music concerts, directing from the harpsichord, and more recently has worked with choirs in regional Victoria. Since 2002, he has worked with the choruses in local theatrical societies as Music Director, and since 2017 he has directed a community choir in South Melbourne.