Dictionary of Sydney staff writer
A Scottish immigrant, McCormick arrived in Sydney in February 1855, aged about 20. He worked first as a joiner and became involved in amateur musical societies. He briefly trained as a teacher at Fort Street Model School in 1863, and was then appointed teacher-in-charge of a school in suburban St Marys. From 1867 he taught at the Presbyterian school, Woolloomooloo, and then at Dowling (Plunkett) Street Public School from 1878 until 1885. He also served as precentor (music director) of the General Assembly of the Presbyterian Church of New South Wales.
McCormick's principal claim to fame is as author-composer of the national song 'Advance Australia Fair', which was first sung at the St Andrew's Day concert of the Sydney Highland Society on 30 November 1878. The Sydney Morning Herald described the music as 'bold and stirring', and the words as 'decidedly patriotic' – it was 'likely to become a popular favourite'. Under the pen-name 'Amicus', McCormick later had the music and four verses of text published by WH Paling & Co Ltd.
The first clear recognition of its future place in Australia's national consciousness came in Sydney on 1 January 1901, when it was sung (with a slightly modified text) by a choir of 10,000 voices at the inauguration of the Commonwealth of Australia in Centennial Park. In 1907 the New South Wales Premier was already describing the song, according to its publisher, as 'our national anthem'. 
In a letter in 1913, McCormick described how he came to write the song. After attending a concert at which national anthems were sung, he
... felt very aggravated that there was not one note for Australia. On the way home in a bus, I concocted the first verse of my song, & when I got home I set it to music. I first wrote it in the Tonic Sol-fa Notation, then transcribed it into the Old Notation, & tried it over on an instrument next morning, & found it correct … It seemed to me to be like an inspiration, & I wrote the words & music with the greatest ease. 
McCormick also wrote the patriotic song, 'Awake! Awake! Australia'. He died at the age of 83 in 1916 at his home, Clyde Bank, in Birrell Street, Waverley, and was buried in Rookwood cemetery. His obituary in the Sydney Morning Herald observed that 'Advance Australia Fair' was 'recognised as something in the nature of an Australian National Anthem'. 
Tenor Peter Dawson's famous recording of the song, made in 1935, did much to enhance its popularity. Until 1952, a shortened version was used as the news theme on ABC radio. The federal Whitlam Labor government first proclaimed it the national anthem, replacing 'God Save the Queen', in 1974, and its status was finally confirmed by the Governor-General in 1984.
'Death of Mr PD McCormick', Sydney Morning Herald, 31 October 1916
Jim Fletcher, 'McCormick, Peter Dodds (1834?–1916)', Australian Dictionary of Biography, vol 10, Melbourne University Press, Melbourne, 1986, pp 237–238