John McIntosh studied organ privately with Lansing MacDowell, Charles Peaker, and André Marchal, and at the ESM, Rochester, with David Craighead, Catharine Crozier, and Russell Saunders. He taught at the University of Toronto (1957-58) and Toronto's Malvern Collegiate Institute (1961-62) before joining the faculty at the University of Western Ontario, where he was head of the theory department 1962-68 and chairman of the applied music department 1968-76, and where he has continued to teach. He has taught organ performance, literature, and pedagogy, church music, music theory, counterpoint, and orchestration.
As recitalist, McIntosh performed in major Canadian cities, the USA, and Great Britain, and was heard on the CBC. He gave lecture-recitals and masterclasses at several Canadian universities and, at the University of Western Ontario, performed annually as choral conductor, harpsichordist, organ accompanist, and conductor of the university's Ceremonial Brass. Four of his anthems composed for mixed choir have been performed. In 1973, he became organist and choirmaster of St James Westminster Anglican Church, London. He was a member of the RCCO and in 1991 became chairman of its London centre.