[1] Born as Franz Oscar Natzke (as he was sometimes credited earlier in his career) at Wharepuhunga, North Island, New Zealand, he was the son of August Natzke (a native of Brixen, a German-speaking part of Italy), who had emigrated to New Zealand and settled in Ōtorohanga, and Emma Carter Natzke, of Christchurch, New Zealand, who was a singer.
As a boy, the young Natzke worked on his father's farm; he was encouraged and trained as a singer by his mother.
The family was displaced by the recession of the 1920s to Waiheke Island, where Oscar sang as a boy soprano in concerts.
He was aided early in his career by Homer Samuels, husband of Amelita Galli-Curci; John Brownlee, the Australian baritone; and Anderson Tyrer, conductor of the New Zealand National Orchestra.
His widow, Winifred, later married the Oscar-winning American actor, Charles Coburn.