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  • Tactus, Mensuration and Rhythm in Renaissance Music by Ruth I. DeFord
  • Anne Stone
Tactus, Mensuration and Rhythm in Renaissance Music. By Ruth I. DeFord. pp. xii + 504. (Cambridge University Press, Cambridge and New York, 2015. £80. ISBN 978-1-107-06472-0.)

The scope of this book is very large indeed: the theory and practice of musical rhythm and notation over the two centuries of the 'Renaissance', a period in which musical style changed dramatically. It covers terrain last traversed in J. A. Bank's Tactus, Tempo and Notation from the 13th to the 17th Centuries (Amsterdam, 1972), but treats the topic with considerably more subtlety and depth. While the purpose of Bank's analyses seemed principally to be to establish correct performance tempos, DeFord wants to understand how the mensural system was employed by composers to create musical structures and affective settings for text. In the first part of the book, labelled 'theory', DeFord gives us the tools to analyse the rhythmic dimension of the music, and in the second, 'practice', she deploys these tools in a series of case studies ranging from Du Fay's songs of the earlier fifteenth century, to cyclic Mass Ordinary settings of the high Renaissance, to the popular song and dance forms of the later sixteenth century, showing the beauty of the mensural system at play.

The 'theory' portion of the book unfolds in seven chapters that combine a discussion of the writings of the most important theorists over the two centuries with DeFord's own careful analysis of difficult terms and concepts. Two short initial chapters survey the theorists under discussion (including a useful table on pp. 10–14) and offer a primer on the mensural system for the uninitiated. Chapter 3, 'Definitions and Descriptions of Tactus', begins the work of careful philology that is one of the book's most outstanding features. The nuance with which DeFord approaches her subject is put into relief if we compare her definition of 'tactus' with that of Bank in 1972. Bank wrote that tactus is 'the twofold down-up motion of the hand or a baton made by the directing cantor' (p. 7). DeFord's definition of tactus (pp. 51–2), on the other hand, parses it into six inter-related aspects of musical time, of which only the first corresponds to the physical beating that Bank refers to. Tactus as physical motion that articulates a time unit is given the name 'performance tactus', to distinguish it from two other meanings of tactus that play an important role in organizing musical time: 'compositional tactus', discerned from the rate of contrapuntal rhythm and dissonance treatment of a given musical work; and 'theoretical tactus', the unit of measure that functions as timekeeper in a given mensuration. (In modern notation a crotchet in 4/4 would be the 'theoretical tactus' even though a performer might choose to beat minims or quavers, a choice that constitutes the 'performance tactus'.) In addition to these three principal uses of the term tactus, there are three subordinate ones: it can be taken to mean the abstract unit of time corresponding to one of these three qualities (the 'value of the tactus'); a time unit in the mensuration that corresponds to the performance tactus or the compositional tactus (the 'tactusunit'); or the absolute value of any of the three principal definitions of the tactus (that is, its metronome marking).

Crucially, the performance, compositional, and theoretical tactus are not always the same value in a given piece, so that to determine them in relation to one another in a given composition is already to discover much about its mensural character, as we learn in the analyses offered in the second part of the book. Chapter 4 sets the stage for these analyses by exploring the inter-relationship between tactus and musical rhythm in general. The chapter begins by describing mensural structures with a binary versus ternary tactus, then moves on to [End Page 130] consider how tactus functions in specific kinds of rhythmic events such as syncopation and hemiola. The chapter concludes with an important discussion of how the interplay between performance tactus and compositional tactus affects composition. At the...

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