Born on 15 June 1912 at Wharepuhunga, near Te Awamutu, Franz Oscar Natzke was the fourth and last child of Emma Frances Carter and her husband, August Natzke, an immigrant from Germany and the father of nine surviving children from his previous marriage. Oscar's early years were spent on his father's farm, Fernlea, but when he was six the family shifted to Hamilton and he attended school at Fairfield. Subsequent moves were to Clevedon, Patumahoe and finally, in 1920, to Waiheke Island, where his parents took over the running of a private boarding house at Onetangi.
An accomplished pianist and organist, Emma Natzke soon became aware of Oscar's unusual vocal gifts, and with no other tuition available she coached the boy herself. In 1922, however, August Natzke died, leaving the family in a precarious financial situation. To relieve the strain, Oscar left school as soon as he turned 15. For 3½ years he was apprenticed to a blacksmith at Freemans Bay, Auckland. During this time his voice developed into a basso profundo of such remarkable qualities and potential that formal training was desirable and he became a pupil of William Garratt (also known as Gard), a former opera singer then teaching in Auckland.
It was Garratt who introduced Natzke to the Auckland public. As song leader at the popular town hall community sing entertainments, held to benefit the unemployment relief fund, he arranged for his protégé to make his solo début on 27 July 1932. Later that year, when the prima donna Amelita Galli-Curci was appearing in Auckland, at his mother's instigation Natzke sang privately for the eminent soprano's accompanist and husband, Homer Samuels. The pianist had substituted for his ailing wife at the audition and was amazed at what he heard. Early in 1933 the visiting international Australian opera singer John Brownlee was so impressed with Natzke's voice that he gave him some free lessons. Both artists predicted a successful professional future for the young New Zealander, providing he could be sent overseas for advanced training – seemingly an impossibility in the depths of the 1930s depression.
In 1934, however, Natzke was heard by Andersen Tyrer, a touring examiner for the Trinity College of Music, who arranged a three-year scholarship for him at the college. Supported by a fund set up by several Auckland businesspeople (whom he later repaid), Natzke began tuition in London under Albert Garcia early in 1935. Three years later, a chance meeting with the opera producer and singer Vladimir Rosing led to his début at the Royal Opera House, Covent Garden, on 10 October 1938. He was said to be the first student to move directly from training at Trinity College to important roles at Covent Garden. Natzke appeared in Gounod's Faust, George Lloyd's The serf, and later, on a provincial tour with the company, in Wagner's Mastersingers of Nuremberg. In all productions his singing was highly praised. He also began making recordings at this time.
In 1940 Natzke returned to New Zealand to take part in the National Centennial Music Festival and to tour Australasia. On 18 February 1941 he was married in Auckland to Winifred Jean Clements, a well-known Auckland soprano. Early in May he travelled to the United States, hoping to consolidate his career. After appearances in New York and several cities in Canada, he enlisted in the Royal Canadian Navy in March 1943 and was posted to the entertainment division. For three years he toured Canada, the British Isles and Europe with the unit's all-service show, Meet the navy, appearing also in a royal command performance in London and, during 1946, in a film version of the production.
Following his discharge from the navy in March 1946, Natzke took concert work in London and from 20 March 1947 sang the role of Sarastro in Mozart's Magic flute at Covent Garden's postwar reopening season. It was at this time, too, that he altered the spelling of his name, believing that by replacing the final 'e' with an 'a' it was more likely to be pronounced correctly.
A tour of South Africa was undertaken later in 1947 and on 9 April 1948 he made his début with the New York City Opera in Verdi's Rigoletto. Singing leading bass roles, he remained with the company for the next three years, alternating his opera seasons with the many concert engagements for which he was in considerable demand throughout North America. He became a Canadian citizen in 1948.
Natzka gave recitals in New Zealand and Australia during 1949. At the conclusion of the tour he returned to the home he and his wife had established in the United States and resumed his flourishing operatic and concert career. On 23 October 1951 he collapsed during a performance of the Mastersingers in New York, and two weeks later, on 5 November, he died. He was only 39, and was survived by his wife and two sons. Their first child, also a boy, had been accidentally killed in London in 1948.
Commandingly tall, bearded since his navy days, and gifted with a glorious deep voice backed by an enviable physique and stunning charisma, Natzka epitomised the traditional perception of bass opera singers and the robust characters they usually portrayed. Although he was forthright, even blunt when the occasion demanded, Natzka's earlier intolerance and egotism mellowed over the years. Had his life not tragically ended at such an early age, there is little doubt that he would soon have become universally regarded as one of the world's truly great singers.