[1] She was the accompanist for the Festival Singers of Canada under Dr. Elmer Iseler for many years, where she developed her ear for composing mixed-choral works.
[1] An associate of the Canadian Music Centre, Watson Henderson's compositional output includes works for organ, piano, violin, trumpet, string orchestra, and more than 200 choral pieces.
In 1989 her Chromatic Partita for Organ won a prize in an International Competition for Women Composers in Mannheim, Germany.
From 1952 to 1954 she studied piano at the Mannes College of Music in New York City with Hans Neumann (pianist).
While she was the accompanist for the Festival Singers of Canada she began to compose choral music, including her 'Missa Brevis.'