Roger D. Kinkle, a professional musician and record dealer who also authored an encyclopedic jazz reference book, died April 8 in Indiana of a degenerative brain disease. He was 84.Kinkle wrote “The Complete Encyclopedia of Popular Music and Jazz, 1900-1950,” first published as a four-volume set in 1974. He revised the reference book into three volumes in 1996. The work contains the biographies of jazz composers and performers whose careers started before 1950, and includes lists of their significant works and recordings. About 2,150 biographies are included in the revised edition.