This book provides an in-depth study of the late medieval chanson, from Gace Brule through Guillaume Du Fay. It is largely concerned with interpretation of the way accidentals function, not only at the level of local detail but also as part of the overall design. Thomas Brothers thus explores the way inflections are used by the composer as an expressive tool. The background problem to which this study responds is the conceptual difficulty we have in interpreting pitch syntax in this repertory. Support for this approach comes from reference to causa pulchritudinis (‘by reason of beauty’), a justification for chromatic writing first encountered at the beginning of the fourteenth century. In advancing an interpretation of the musical side of the chanson, Thomas Brothers aims to bring standards closer to what has been achieved in study of sister disciplines of art and literature.