Books on rap and hip hop are at ML 3531.
Selected resources:
Encyclopedia of Rap and Hip Hop Culture by Books about film and television music are at:
Some library resources:
Film and Television Music by 
A Research Guide to Film and Television Music in the United States by 
Books on folk music are at ML 3550-3780. Bibliographies are at Ref ML128 .F74.
Selected resources:
Books on popular music in general are at ML3470-ML3504.
Others: Soul, ML 3537; Reggae, ML 3532; Country, ML 3524; New Age, ML 3629.
Dictionaries and encyclopedias, Ref ML102 .P66; Bibliographies, Ref ML128 .P63; Discographies & charts, Ref ML156.4 .P6
Selected resources:
Full-text online from over 400 encyclopedias, dictionaries, and other reference books. Search a topic, build a concept map, or browse information sources organized by subject. Find text, images, sound files, sortable data tables and more.
Blues, Funk, Rhythm and Blues, Soul, Hip Hop, and Rap by Books about rock are at ML 3532. Dictionaries and encyclopedias, Ref ML102 .R6; Bibliographies, Ref ML128 .R6.
Selected resources:
Top 10 Pop Hits by 