In 1913 Hart took over George Marshall-Hall's lecturing duties at the Melbourne Conservatorium of Music in Albert Street, Marshall-Hall having left for London. When a year later Marshall-Hall sent instruction that the Conservatorium was to be closed down, its staff refused to resign and appointed Hart director. Marshall-Hall was subsequently appointed professor of music at the University of Melbourne in 1915, so appearing as a potential rival to Hart's Conservatorium; but such was the anti-German/pro-British attitude during World War I that Marshall-Hall's predominantly German staff did not enjoy the popularity of Hart's more British orientated Conservatorium. Dame Nellie Melba established her school of singing there, and she and her pupils helped shape Hart's work as a composer. He had the overall responsibility for her students' musical training, many of whom made their marks internationally.