Tactus, Mensuration, and Rhythm in Renaissance Music by Ruth I. DeFord (review)

At first blush, Renaissance musical notation appears to have a lot in common with modern musical notation. The note shapes and colors look alike, and the notes are placed on a staff made up of lines and spaces. However, to assume an exact correlation between our present-day notation, especially our methods of notating rhythm, and systems of Renaissance mensural notation, is to be quite certainly mistaken. In her book, Tactus, Mensuration, and Rhythm in Renaissance Music, Ruth DeFord describes how composers and theorists of the fifteenth and sixteenth centuries conceived of and notated rhythm and musical time and addresses the many difficulties in understanding rather foreign rhythmic structures.

The thoroughness of DeFord’s research is enviable. She leaves no stone unturned when considering the various options for interpreting Renaissance rhythmic notation. The fastidious nature of DeFord’s survey, however, is not for the faint of heart. Rather than providing straightforward guidelines for applying a single theorist’s ideas, she presents the reader with a variety of options and ideas. Throughout the book, she describes mensural notation and Renaissance rhythm not as a “single, unified system, but as a collection of diverse practices that varied with time, place, genre, and composer” (p. 3).

DeFord’s volume is divided into two parts, the first focused on theoretical sources and the last steeped in practical concerns regarding repertoire. Following a brief introduction that lays out the basic issues at hand in the volume, she explores the extant sources pertaining to Renaissance rhythm. In chapter 2, an essential introduction to specialized terminology eases the reader into the complexities of Renaissance rhythm, making the information that follows accessible to a wider audience of students and scholars. Chapters 3 through 7 address topics related to musical tactus, a unit of musical time which DeFord describes as the juncture between the abstract values of mensural notation and actual time values in performance. The final section of the book focuses on repertoire, honing in on the works of some of the most well-known composers of the period: Ockeghem, Busnoys (or Busnois), Josquin, Isaac, Palestrina, and Rore. DeFord concludes Part II with a brief chapter on popular song, which contrasts sharply with the largely sacred, vocal repertoire discussed earlier in the section. A succinct conclusion contains a list of the important ideas that govern tactus, mensuration, and rhythm, and leaves the reader with descriptions of how these concepts affect the process of editing and performing Renaissance music.

Chapters 1 and 2 provide a foundation. The first chapter is a thorough guide to the fifteenth- and sixteenth-century theoretical sources. In chapter 2, DeFord goes back to the basics, introducing the different mensuration signs, note shapes, and ligatures, and describing the various levels of mensural organization from largest to smallest: mode, tempus, and prolation. DeFord establishes her own vocabulary to refer to elements of mensural organization, which is especially important considering the terminological inconsistencies in the extant theoretical and musical literature. After setting the basic parameters of this familiar, yet foreign, rhythmic language, DeFord presents the methods of complicating rhythms. Finally, she outlines the indicators of particular mensurations in the absence of signs, which are especially important because many Renaissance composers did not consistently notate mensurations.

In the remaining theoretical chapters (3–7), DeFord explores the idea of tactus, which she describes as having three primary meanings: (1) the physical motion measuring time in performance, (2) the unit of time that governs the contrapuntal structure of the piece (compositional tactus), and (3) the unit of time associated with a mensuration sign in music theory (theoretical tactus). In chapter 3, a thorough study of the works of fifteenth- and sixteenth-century theorists shows how tactus contributes to both the theoretical and audible structuring of time in music. In chapter 4, “Tactus and Rhythm,” DeFord examines how tactus creates effects such as surface rhythm, syncopation, and hemiola...