[1] Recently a colleague of mine found me in a coffee shop reading Critical Nexus: Tone-System, Mode, and Notation in Early Medieval Music by Charles Atkinson. Upon hearing the title he made an audible Ieck! and scurried off to avoid any further conversation. Sadly, this is not an unfamiliar or even unexpected response. For those who accidentally, or heaven forbid willingly, venture into the realm of early and mode theory, most are quickly confused by the vernacular and a concept of tone that only vaguely resembles the tonal system of today. For example, even the simple definition of exactly what constitutes a mode versus a is unclear. modern concept of scale, or mode for that matter, is simply a set of particular intervallic patterns starting on a particular note; however, in the Middle Ages this was not a consistent concept. terminology of these conventions differs considerably within the primary sources of the early Middle Ages; therefore, we often are forced to grope somewhat blindly without a reliable cipher to decrypt the various contextual rules.[2] Critical Nexus seeks to clarify the hazy transition from early Greek music theories of the Greater and Lesser Perfect systems to the early medieval tonal, modal, and notational systems. book draws various early theoretical treatises together and presents them in an accessible, unified study. Atkinson is particularly successful in navigating the period sources and tracing the lineage of changing definitions and problems of translation. great virtue of the book is that it is at once the most comprehensive and the most intelligible treatment of early theory to date. Atkinson's scholarship is thorough throughout and he shows an admirable sensitivity to the balance between theory and practice. One gets the impression that this book was both a labor of love and the type of work that only comes out of decades of deliberation.[3] Chapter 1 is a general primer on Greek theory, concerned primarily with the treatises by Boethius, Martianus, and Cassidorus; it also touches briefly on works by Donatus, Aristides, and Isidore.(1) Atkinson avoids confusion at the beginning of the chapter by clearly defining his terminology and his conception of the Greater and Lesser Perfect Greek Systems, affinities, and transposition. This primer is clear enough to provide general background for those unfamiliar with early theory. What separates Atkinson's work from much early theory scholarship is the simplicity with which he approaches the subject without trivializing the material. In addition, the footnotes are plentiful and concise; therefore, the chapter is helpful to both students with a limited knowledge of the early history of music theory and to scholars. My only criticism is that the chapter could have included a few more figures to connect the theoretical concepts. For example, in the survey of the common Greater and Lesser Perfect Systems and discussion of the monochord for determining the geometric divisions, it would have been helpful to have a figure illustrating these points on the monochord (in addition to Atkinson's figure 1.6, which merely shows the results of the divisions on a staff). Those familiar with early mode may find such an addition somewhat rudimentary, but it would have provided additional insight to newcomers. Similarly, one of the more confusing areas for non-early music specialists is the switch from a modern concept of modes to the medieval concept of mode. While Atkinson includes an example of Boethius's diagram of the modes using the Greater and Lesser Perfect Systems (his example 1.8), it would have been helpful had he also included a modern interpretation of modes and octave species to illustrate their overall intervallic structure and ranges in relation to one another, such as that in Calvin M. Bower's The Modes of Boethius.(2)[4] last section of chapter 1 (29-49) is its best feature. …