Constant J. Mews is Director of the Centre for Religious Studies, Monash University in Victoria, Australia. Carol J. Williams is a Senior Lecturer at Monash University, specializing in medieval music. John N. Crossley is a Professor Emeritus at Monash University. Catherine Jeffreys is an Adjunct Research Associate at Monash University.

"This important publication increases the accessibility of a less-well-known medieval treatise on music theory devoted to the Gregorian chant repertoire for Mass and Office. [...] This welcome new edition and English translation of the Tractatus by a team of Australian scholars introduces the treatise by identifying the sources of Guy's teaching, sketching the history of his abbey in the late thirteenth and early fourteenth centuries, and exploring the treatise's relationship to the Cistercian and Dominican chant traditions." Joseph Dyer, The Medieval Review 18.03.18

• AcknowledgmentsAbbreviationsIntroductionOutline of the Tractatus de tonisTractatus de tonis: Text and TranslationAppendicesI. Deleted materialII. Explanatory materialWorks CitedManuscript sourcesPrimary sourcesSecondary sourcesLexiconGlossaryOnomastic Index