It’s a long, long way to Tipperary was written by Henry Williams and Jack Judge in 1912, and performed in British music halls. It became popular in WW1, as a British marching song. Written in 1917, Over there by George M. Cohan was a rousing popular song, that echoed the wave of patriotism that swept the US after war was declared by President Wilson in April of the same year. The famous Italian tenor, Enrico Caruso, did much to make the tune popular, making two recordings in English and French. Many songs were sentimental, often dealing with themes of the separation of sweet-hearts, or mothers missing their sons, who were either leaving or absent. A good example is the song Keep the home fires burning (1915), which encourages those at home to remain steadfast and strong.
Many soldiers had phonographs and 78 rpm records in the trenches. The English company, Decca, made a popular compact phonograph, called the “Trench Model."
WEBSITES: The following sites contain examples of WWI sheet music, including much background information:
Brown University Library Center for Digital Scholarship: World War I Sheet Music
Duke University: Digital Collections: Historic American Sheet Music (1914-1918)
Library and Archives Canada: Canadian Sheet Music of the First World War
Europeana 1914-1918: Search using “Audio Interview” AND your topic. For example "Audio Interview" AND Trenches. Note: some interviews are not in English.
Library of Congress: American Memory
"The Nation's Forum Collection consists of fifty-nine sound recordings of speeches by American leaders from 1918-1920. The speeches focus on issues and events surrounding the First World War and the subsequent presidential election of 1920. Speakers include: Warren G. Harding, James Cox, Calvin Coolidge, Franklin D. Roosevelt, Samuel Gompers, Henry Cabot Lodge, and John J. Pershing. Speeches range from one to five minutes."
The Great War Archive, University of Oxford: Sound Archive
This archive includes many interviews with WWI veterans. Browsing by keyword, such as ‘Gas warfare’ or ‘War at sea’ produces interviews on those subjects.