to be the latter part of the 11th or beginning of the 12th century. The work throws much light on the system of harmony of the period. References "Johannes Afflighemensis", in The New Grove Dictionary of Music and Musicians, ed. Stanley Sadie. 20 vol. London, Macmillan Publishers Ltd., 1980. External links musicologie.org Complete note: sources, editions, bibliography, comments. Digital facsimile of De musica and other treatises from the Library of Congress, MS ML 171 C 77 (Phillips 1281). English music theorists Year of birth unknown Year of death unknown Medieval music theorists