From 1902 to 1917, he was head of the music division of the Library of Congress, and as such created a significant music library. Since 1915, he was also editor of The Musical Quarterly. As a writer, he specialized in the history of early (before the 19th century) American music. He died in New York City, aged 55.
The Society for American Music was created in his honor, and initially named after him.
- A Bibliography of Early Secular American Music (1905, rev. ed. 1945)
- Early Concert-Life in America (1907)
- The Star-Spangled Banner (1914)
- Catalogue of Opera Librettos Printed before 1800 (2 vol., 1914)
- Early Opera in America (1915)