Brook's research interests included Renaissance secular music, 18th- and 19th-century music and aesthetics, music iconography, and the sociology of music. He served as editor of a facsimile edition of the Breitkopf Thematic Catalogues (New York, 1966), an important source for the identification and dating of 18th-century compositions. His interest in music bibliography and its history led him to found Répertoire International de Littérature Musicale (RILM), the first international bibliography of music scholarship, in 1966; he served as the project’s Editor-in-Chief until 1989.
Although he was known principally for his work in classical music, in the later years of his life Brook became fascinated with ethnomusicology. He often sought out and trained budding music historians in how to bring their reports and studies of local music traditions into the mainstream, academic world of music history.
He founded the Research Center for Music Iconography in 1972. He also founded the Barry S. Brook Center for Music Research and Documentation in 1989, which was named after him upon his death. It is located at the Graduate Center of the City University of New York.
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