Born in Toronto, John Armstrong studied composition at the University of Toronto and the University of Michigan where he received his Doctorate in 1983. His teachers included George Wilson, Pulitzer Prize winners Leslie Bassett and William Bolcom, as well as the celebrated pedagogue Nadia Boulanger.

John won prizes in both the William St. Clair Lowe and Sir Ernest MacMillan competitions sponsored by the Composer’s, Author’s and Publisher’s Association of Canada (now SOCAN). He has been commissioned and performed by musicians such as William Beauvais, Ray Sealey, Louis Trépanier, Catherine Donkin, Alan Torok, Norbert Kraft, Robert Riseling, Dorothea Brinkmann, Douglas Perry, Jane Perry, Jill Dreeben, Elizabeth Volpé, Charles Hamann, Doreen Taylor-Claxton, Sandra Mangsen, Craig Sylvern, Janine Gaboury, SaxArt, The Canadian Guitar Quartet, The Continuum Consort, The Victoria Guitar Trio, The Alliance for Canadian New Music Projects, The Guitar Society of Toronto, The Cantata Singers of Ottawa and Coro Vivo Ottawa. He has received multiple grants and commissions from the Laidlaw Foundation, the Canada Council, the Ontario Arts Council, Alberta Culture, the Canadian Broadcasting Corporation and the City of Ottawa. Performed and broadcast throughout Canada, his music has also been played in Belgium, France, Great Britain, Korea, Norway, Vietnam and the United States. His music has been published by Alberta Keys Music Publishing (Calgary), New Art Music Editions (Winnipeg), Oceanna (Bobcaygeon), Cypress (Vancouver) and the Canadian Music Centre (Toronto).

Although primarily a composer of concert music, he has also written for film, dance and theatre; he is well known in Ottawa for his 12 collaborations with Odyssey Theatre. Having taught at a number of universities in Canada and the United States, John Armstrong is currently an Adjunct Professor of Composition and Theory at the University of Ottawa.