In 1911, Eaton co-founded the Society of Women Musicians with composers
Katharine Emily Eggar and
Marion Scott. The first meeting was held in October 1911, when Eaton was elected treasurer; she also spoke at that first meeting. She served a term as president of the Society from 1916 to 1917. Gertrude Eaton was also active on the issues of suffrage and prison reform, and served a term as president of the
Howard League for Penal Reform. Eaton used her musical training to teach fellow activists to use their voices for confident public speaking. As secretary of the
Women's Tax Resistance League, in summer 1911, her household silver was seized when she refused to pay taxes as a suffrage protest. She also evaded the census in 1911 as part of an organized suffrage protest. She was said to be "instrumental" in getting penal reform on the agenda of the
League of Nations. Eaton was one of the British delegates to the
Women's International League for Peace and Freedom meeting in
Zurich, Switzerland in 1919. Eaton died on 8 March 1939, aged 77 or 78, at
Hampstead. Her colleague
Margery Fry wrote in an obituary of Eaton, "She would take endless pains to help a cause or an individual when her sympathy was aroused." ==References==