This song booklet, compiled and distributed by the YMCA, was a staple among the soldiers of the American Expeditionary Forces during World War I. (U.S. Air Force photo)

This song booklet, compiled and distributed by the YMCA, was a staple among the soldiers of the American Expeditionary Forces during World War I. (U.S. Air Force photo)

This song booklet, compiled and distributed by the YMCA, was a staple among the soldiers of the American Expeditionary Forces during World War I. (U.S. Air Force photo)