American National Biography includes biographical profiles of each of these women. Willa Cather's 1913 article on Louise Homer, Geraldine Farrar, and Olive Fremstad includes photographs and is supplemented with links to online sound recordings.
Images of singers often appeared on sheet music covers. Researchers can use the Sheet Music Consortium's database to search across sheet music collections at UC-Los Angeles, Indiana University, Johns Hopkins University, and Duke University. A search for Nora Bayes retrieved 82 records, including Ladies First (at left) from Johns Hopkins.
Chronicling America provides access to more than 3.7 million newspaper pages from more than 500 newspaper titles published in 22 states and the District of Columbia between 1860 and 1922. Try searching for notable women singers from the first quarter of the 20th century. For instance, a search for Alma Gluck retrieves images and stories about Gluck, as well as advertisements such as the one at right from the New York Tribune (July 8, 1916).