Although, according to the author, much sound research, has been done in the Dufay era in recent years," Charles Hamm's book marks the first time an attempt has been made at a comprehensive chronology of the works of this composer. Professor Hamm approaches all Dufay's compositions from the point of view of mensural practice, and has been able to date each piece more precisely than would have been possible in a chronology based on manuscript studies or stylistic analyses. He has divided the works into nine groups, according to details of mensural usage, and on the basis of datable works...