Among different extant written sources of Tibetan music, namely, theoretical works, notations and manuals, the “Treatise on Music” written in the thirteenth century by prominent Tibetan scholar Sa skya Paṇḍita Kun dga' rGyal mtshan (1182-1251) is the earliest and most informative one. As this work includes three chapters almost entirely dedicated to the theory of vocal music production and composition techniques (with a small part relating to musical instruments), the treatise seems to be very important for getting deeper knowledge of the medieval Tibetan vocal tradition. The translation and multidisciplinary analysis of this source, aided by consulting other written sources of Tibetan music and main research conducted in that scientific sphere, displayed various features of Tibetan vocal system as it was perceived by Sa skya Paṇḍita, e.g. close relations between articulated phonemes and melodic movement, lack of scale or mode system, rhythmic structure utterly dependent upon the poetical meter, and many others. Taking into account highly developed vocal (and musical) systems of the neighboring countries in the period under consideration, the tradition of singing described in detail in the “Treatise on Music” seems to have been a unique product of the Tibetan world. Archaic as it was, this tradition would have had little opportunity to become known to the scholars of the modern times if it were not a Tibetan Buddhist scholar trained in the lines of Indian scholastic tradition who described it in his treatise. As there is still not so many scientific works dedicated to the history of Tibetan music, these findings can contribute to the construction of consistent narration about the development of musical art in Tibet. Used in worldwide context, they may help to define some general trends in the history of music of various ethno-cultural societies.