Western music in general and Renaissance polyphony in particular show a strong theoretical focus on intervals. The distance between pitches is the starting point for composers designing their melodies as well as superposing them in a polyphonic texture. McKinney's book goes beyond the contrapuntal complexity of balancing melodic and polyphonic implications. Closely examining Willaert's most celebrated madrigals (the ones included in the illustrious 1559 collection Musica nova), he detects an underlying theory of interval affect, linking certain intervals to the expression of specific textual contents.

In five chapters, McKinney develops his theory, applies it to the Musica nova madrigals, and extends his findings to other madrigals by Willaert and some other composers. The first chapter briefly introduces the diverse aspects of the book, providing some music historical background, but also quickly engaging in the music theoretical core of the book. The writings of Zarlino and Vicentino are announced as the central foundations for McKinney's approach, and the novelty of their systematic discussion of the affective qualities of intervals is highlighted. After having gone briefly into text-music relations in general, McKinney assembles what other analysts have written about the exordium of one famous Musica nova madrigal, “Aspro core e selvaggio e cruda voglia.” Readers familiar with this repertoire will easily recognize that major steps and sonorities (and especially the 6–5 suspensions) reflect the harshness and cruelty of the first verse, while minor intervals gain importance in the second verse (issuing among other things from the B flat that is introduced with the dolce, humile, angelica figura of Petrarch's muse).

The second chapter retakes the analysis of “Aspro core” after having established the theory of interval affect on the basis of Zarlino's and Vicentino's major publications of the 1550s. While the former theorist is more closely related to Willaert's musical output and actually quotes passages from Musica nova madrigals, the latter provides a more systematic overview of musical intervals, indicating their character as tense (incitato) or slack (molle) in a melodic context. For vertical intervals (i.e., between simultaneously sounding notes) the associations appear only indirectly from Zarlino's and Vicentino's descriptions, although it seems that McKinney would have liked them to provide an equally straightforward table of happy and sad sonorities. Analyzing mainly the density of major and minor sixths and thirds in numerous examples, he comes close to such classification. The extensive application of it in chapter 3 to five Musica nova madrigals in their entirety provides revealing analyzes with considerable sense for detail.

Full-score transcriptions of the madrigals are annotated with a sort of figured bass. Roman numerals indicate the degree of the lowest sounding note in relation to C or to F (for pieces bearing a flat signature), with uppercase and lowercase distinguishing major and minor sonorities. Although this system helps to locate the interval structures upon which McKinney's analyses are based, it is not very sophisticated and seems to pass by at least some subtleties that are central to music predating the common practice era. The extrapolation of qualities of dyadic intervals to constellations of three and more voices is one aspect that might have deserved more attention. Another issue is the interdependence of the theoretical systems of gamut, hexachord, and mode. Going into this complicated matter would definitely allow McKinney's analytical observations to reach another level of music theoretical insight, but at the same time would have exceeded the scope of his monograph.

The presented analyzes are successful in the first place because they demonstrate how subtle poetic elements are reflected in the polyphonic fabric of the pieces. This is no surprise, as many have come to this conclusion before, but McKinney reaches it by in-depth discussions of individual madrigals. In the final chapters, he takes the theory of interval affect to other madrigals by Willaert and by composers under his influence (beginning with Vicentino and Zarlino). This transfer is not always as effective, and more differentiation could have been reached by widening the focus from single intervals to the process of harmony in its temporal unfolding throughout the piece. However, a solid analytical approach of the mid-sixteenth-century madrigal can only be welcomed, as it has been somehow neglected in much of the literature on this repertoire.