Russian music theory has a strong foundation in Greek and Latin source studies. This status quo is preconditioned by a rich tradition of instruction of the Greek and Latin languages in the Russian pre-revolutionary culture, as well as by some powerful relations of the Russian Orthodox theology with the Greek and Byzantine history.  During the 1980s and 1990s (1985), several dissertations dedicated to the Western early music theory were successfully defended at the Moscow Conservatory. Most of them appeared under the influence of Prof. Yury Kholopov. During the most recent years, two books came out from Moscow Conservatory. One is the bilingual edition of Boethius' Fundamentals of Music (2012) by Lebedev, and the other is Ptolemy's Harmonics (2013) translated by Vyacheslav Tsypin. The latter incorporates a translation of Porphyry's Commentary to Ptolemy's Harmonics — the first translation of the Commentary into a modern language.
This paper will touch upon some closely interrelated fundamental categories of the early music and reveal the discrepancies between Western tradition (Boethius, Ingemar Düring, Frieder Zaminer, Andrew Barker, Thomas Mathiesen, Calvin Bower, Jon Solomon etc.) and the Russian one (mostly scholars from the Moscow Conservatory). Ptolemy's famous definition at the very beginning of his Harmonics is the definition of ‘harmonia’ rather than that of either ‘harmonic science’ or ‘harmonics’.  Another point of discussion is the author's observations over the term ‘modulari’ and its derivatives (‘modulatus’, ‘modulandi’, ‘modulatio’, ‘modulamen’) in Boethius' early treatises. The author conceives these two new interpretations—the most comprehensive understanding of ‘harmonia’ as a pitch system of some type and ‘modulatio/modus’ as two paradigms of an early comprehension of the notion of ‘lad’—in order to render further support to Yury Kholopov’s  universal concept of harmony.