She began piano lessons as a child in Chilliwack, and in her teens she studied voice in San Francisco with a Mr Jaffe(y). She also studied voice in Vancouver and with Colin Ashdown in Halifax, where she had settled in 1931 after her first marriage. She became acquainted with folk music in 1938 when she served as piano accompanist for the English singer Eve Maxwell Lyte in a recital that included songs collected by Helen Creighton.
Known at this time as Nina Finn, she sang on Creighton's CBC radio program in 1939 and travelled with her on field trips. In A Life in Folklore, Creighton wrote of Finn: 'Hers was the only trained voice that satisfied the folk singers. When she was through there was no singing [the songs] over again "right," for [the folksingers] could tell she loved them as much as they did'. Creighton recorded Finn's versions of several songs for the (US) Library of Congress. While working 1943-7 in Ottawa for the music and sound department of the National Film Board of Canada (NFB) Finn incorporated in movie soundtracks much folk material from the board's recorded collection. She also collaborated with Marius Barbeau at this time.
In 1948, as Emma Caslor - the names were taken from her ancestors - she began a professional career as a singer in Vancouver, performing until the early 1960s on CBC radio and TV and recording many songs for CBC IS (LPs 22, 65, 66, 67, 68, 103, 104, 105, 160, 161). John Avison often served as her accompanist. She appeared at the 1958 Stratford Festival. Her repertoire, initially drawn from Gaelic and Anglo-Saxon songs, eventually embraced music from many other folk cultures in Canada, including that of west coast Aboriginals. She also sang Elizabethan songs.
Caslor taught her daughter Gretchen (Joan Bartley) Grinnell, née Finn (born 23 December 1932 in Prince Rupert, BC; died 26 October 2016 in Vancouver, BC), who studied voice also with Colin Ashdown and piano 1946-7 in Washington, DC, with B. Gunn. As a child, Grinnell sang for the soundtracks of NFB productions. Later, though by profession a psychotherapist, she gave concerts of folk music in Vancouver.
See also Folk music, Anglo-Canadian; Gaelic.