As the editors observe in their introduction, the publication of a medieval music theory treatise represents a venture into "new territory" for the TEAMS Varia Series. The treatise in question, the Ars musice of Johannes de Grocheio (ca. 1275, as the editors convincingly argue), is a good choice for several reasons. While medieval music theory treatises seldom make for very exciting reading, the breadth and (in places) originality of Grocheio's teaching make his treatise an important document for understanding the intellectual, social and musical environment of late thirteenth-century Paris. In fact, Grocheio structured his teaching around the three kinds of music found at Paris: vulgalis (of the people), mensurata, and ecclesiastica, which latter he claims "is effected from these [previous] two" (61). Grocheio's attention to contemporary musical performance has made Ars musice a favored destination for medieval musicologists, even for those who do not specialize in music theory.
Johannes de Grocheio's Norman roots were confirmed by Christopher Page nearly twenty years ago in an article that also provided an English translation of portions of Ars musice.  Of the four towns in the region named Gruchy or Grouchy, one not too far distant from Coutances appears to be the most likely candidate for the author's birthplace. The contents of the treatise leave no doubt that Johannes had thoroughly absorbed the philosophical education of his day, and he endeavored to apply some of its modes of thought to the writing of music theory. One of the sources of Ars musice concludes with a phrase identifying him as a Magister: "explicit theoria magistri iohannis de grocheio."
The two manuscripts that transmit the treatise, both likely copied from the same source, provide a context for the work. One (London, BL, MS Harley 281; early 14th c.) contains exclusively musical treatises, most prominently the works of Guido d'Arezzo (d. 1050). In the other manuscript (Darmstadt, Univ.- und Landesbibliothek, MS 2663; 13-14 c.), Ars musice is the single musical work in a miscellany of theological and moral tracts. Approximately half of the Harley manuscript is occupied by the unique copy of the Tractatus de tonis (ca. 1300) of Guy de Saint-Denis.  The editors, who offer informative descriptions of both sources, suggest that Guy may have been responsible for the inclusion of Ars musice, which "increases the possibility of a personal connection between the two theorists" (13). The Harley manuscript forms the basis of the present edition, but the editors have made a fresh transcription, assisted by an earlier transcription by Sandra Pinegar, that corrected errors in the earlier edition of Ernst Rohloff. The editors duly note variants between the two sources and the presence of corrections added by different hands, H2 identified as being that of Guy de Saint-Denis himself.
The editors have divided Ars musice into forty-three sections, each subdivided into individually numbered subsections. I find this more helpful than Rohloff's serial numbering of all the sentences from 1 to 293, and it should be adopted for future citations of Grocheio's work.  Following the editors' introduction there is a detailed "Outline of the Ars musice" (33-40) that indicates the subject discussed in each subsection of the treatise, thus giving immediate access to whatever topic might correspond to the reader's interest. The text is clearly laid out, the Latin text punctuated according to rules explained in the introduction, with the English translation on facing pages. An ample "lexicon" (131-54) indexes key terms in the Latin text, and a separate index of "names, words, and places" can be used to locate, for example, references to Aristotle, which are quoted generously (in medieval Latin versions, but with the standard Bekker references) in the notes. Omitted from the index are two references each to the Physics and to the Metaphysics, probably because Grocheio attributed them only to the "philosopher" (76-77). All four references are, however, duly recorded in the footnotes to the translation. A comprehensive bibliography lists primary sources and important secondary literature. The notes direct readers to modern editions of the secular pieces mentioned in the treatise, but Latin chants are identified only by their liturgical assignation. Nor is there a separate index of musical pieces. This is unfortunate, since many who discover this affordably priced edition/translation might not know where to find modern printed sources for the chants cited by Grocheio.  Inserted in the footnotes are several musical examples, for example, the "intonation formulae," brief pieces whose melodies epitomize the peculiar characteristics of each of the eight ecclesiastical modes. A chart (Fig. 2) inserted among the footnotes that illustrates mutations from one hexachord to another is incorrectly captioned "How consonances and concords are differentiated" (120). 
Grocheio's treatise, his only known work, is addressed to an unidentified group of iuvenes who had given him "very great support for the necessities of my life" (43). Since university students paid their teachers directly for instruction, this comment sets up a connection with the University of Paris, albeit not with the official teaching program, which was devoted almost exclusively to the works of Aristotle. I doubt that these private students can be identified with "young monks" of the Collège de Saint-Denis, as the editors propose. They would have had no financial resources at their disposal with which to support a secular master and scarcely needed the basic information supplied by Grocheio about chants of the Mass and Office, which they sang every day. They would have been baffled by the author's many references to secular music and music making and would have had little use for the information that the dance known as a ductia "is said to be effective against the passion that is called love sickness [amor hereos]."
Ars musice treats the usual concepts of consonance, basic intervals, definitions of music including the Boethian threefold division of musica (which Grocheio rejects), and musical notation, inter alia. Vocal music is divided into cantus and cantilena, but the author by no means neglects instruments or instrumental music, organum and discant, modal rhythm, musical genres, and the principles for composing polyphonic music. He concludes the treatise with an overview of ecclesiastical music, the eight tones/modes, and individual chant genres (invitatory, hymn, etc.).
In the prologue to the treatise (0.1-6) Grocheio evokes the philosophical plane on which his exposition will be developed, a factor to which the editors draw attention in their introduction (6-9). Knowledge of music is a prerequisite for "a complete knowledge of moving things and movements" (de moventibus et motibus) (43), a phrase that inevitably conjures up the many pages Aristotle devoted to motus as a principle to explain the process of change in nature. Also Aristotelian in derivation is the assertion that sound is one of the proper sensibles and as such an object of the apprehensive potency (potentia apprehensiva, translated as "apprehensive ability"). Grocheio then proclaims his intention to proceed from the general to the specific, following the example of Aristotle in the Physics. He also declares that the model to be followed in the discussion of secular music and polyphony will be the technique employed by Aristotle in the three-book version of De animalibus: De historia animalium, De partibus animalium, and De generatione animalium (66-67)--a process of moving from the general to the specific.
As technical manuals, medieval music treatises require of the reader and translator a specialized understanding of traditional terminology and theoretical constructs. Required of translators, who know all about intervals, hexachords, the musical (Guidonian) hand, mutations, species of fourths and fifths, the ecclesiastical modes/tones, etc., is the ability to grasp how each medieval author conceptualized musical "space" in his own terms. Also essential is a familiarity with the chant repertoire and the liturgical framework in which it resides. In addition, one must bring to Grocheio's treatise an alertness to essential concepts of thirteenth-century philosophy and theology. The present translation tends toward literalism, normally following (it seems) the word order of the Latin whenever possible. Since the most frequently used term in the treatise, the polyvalent cantus, has by design been left untranslated, it is left to the reader how best to construe its meaning in various contexts. Generally speaking, words that mean the same thing ought to be translated similarly, but in a way that demonstrates understanding of the conceptual framework within which they are used. For example, in the prologue immediatius signifies the intimate link between music and the praise of God, and the translation "[music] is more immediately and wholly ordained for the praise and glory of the Creator" seems acceptable (43). Later, however, immediate is rendered as "without mediation" ("the human soul, created from the outset without mediation, retains the species or image of its Creator" (51)). Here, the translation "directly" might have better conveyed the theological teaching that God forms each human soul through a singular, unique creative act (hence no transmigration of souls). In a passage concerning the performance of the Kyrie and Gloria, immediate is translated "directly" with reference to the collect. If someone did not already know that the collect follows the Gloria or (in its absence) the Kyrie, I do no know how the phrase "says directly" (109) would be understood. Something like "immediately thereafter" might be preferable to clarify the temporal succession.
Occasionally, words need to be supplied to avoid an awkwardness or misunderstanding. For example, in the description of the Sanctus one reads that "this earthly and militant church is a sign and an image of that heavenly triumph in which the angels and archangels are declaring without end: Sanctus..." (111). While not far from the mark, a more accurate translation might read: "this church, earthly and militant, is a sign and image of that heavenly, triumphant [church], in which there are angels and archangels saying without end: Sanctus." This version renders more accurately the intended contrast between the earthly and the heavenly "cities," not between the earthly church and a "heavenly triumph."  In the translation of Grocheio's description of the Agnus dei occurs the odd phrase "when there is a celebration for the dead" (cum celebratur pro defunctis) (113). Here, the understood "missa/Mass" should have been supplied, thus bringing the passage into line with a parallel passage a few pages earlier (correctly translated), which says that the Gloria is omitted at Mass "when it is celebrated for the faithful departed" (cum celebratur pro defunctis fidelibus) (109). Unfortunately, the rendering of the opening phrase of this latter passage reverses Grocheio's meaning: "the Mass is often found without [the Gloria], which occurs in a season of sadness or of sorrow." Grocheio's point is that the Gloria is omitted during such seasons.
The editors draw attention to how "notoriously difficult" it is to translate technical terms, and they modestly present their translation as "no more than an interpretation (and not the final word) on the Latin text" (17). To be fair, Grocheio is not immune from lapses into obscurity, and Latin technical or philosophical terms are often weighted with meaning that no single English term can communicate. Nevertheless, Constant Mews and his colleagues have generously offered scholars both a reliable text and a more than adequate annotated translation of Grocheio's Ars musice. The author, who did not want to be counted among "certain theorists [who] conceal their activities and discoveries, not wanting to make them public to others" (43), would have approved.
1. "Johannes de Grocheio on Secular Music," Plainsong and Medieval Music 2 (1993): 17-41; reprinted in idem, Music and Instruments of the Middle Ages (Aldershot: Ashgate, 1997).
2. For an edition of the treatise and facsimile of the tonary, see Sieglinde van de Klundert, Guido von Saint-Denis, Tractatus de tonis: Edition und Studien, 2 vols. (Bubenreuth, Germany: Hurricane Publishers, 1998).
3. Ernst Rohloff, Die Quellenhandschriften zum Musiktraktat des Johannes de Grocheo (Leipzig: Deutscher Verlag für Musik, 1972). The Harley and Darmstadt sources are reproduced in facsimile on facing pages with an edition and German translation of the treatise.
4. A practical guide to modern printed sources and to facsimile editions of chant manuscripts published in the series Paléographie Musicale is John R. Bryden and David G. Hughes, eds., An Index of Gregorian Chant, 2 vols. (Cambridge, MA: Harvard University Press, 1969). Indices of manuscript antiphoners of the Office are available through the CANTUS database hosted at the University of Waterloo (Canada): http://cantusdatabase.org. In his edition Rohloff provided a basic Conspectus cantuum et cantilenarum (199-201), but with only minimal information about the chants.
5. On the bottom row of the chart B-olle should obviously be B-molle.
6. Rohloff suggests for "hereos" the reading ἔρως.
7. Ecclesia enim hec terrestris et militans signum est et ymago illius celestis triumphantis, in qua sunt angeli et archangeli sine fine dicentes: Sanctus... (110).