Modern Dominican books reproduce the shape of the neumes in the medieval manuscripts of our music, which were based on the Humbert of Roman Codex exemplar of 1254, which still exists as MS 1 in the Domincan Archives in Rome. In order to sing our music properly, cantors need to know the system of interpretation explained in the treatises of Jerome of Moravia (d. after 1271. probably Scottish), a Dominican musicologist, who codified traditional practice. An image of his treatise De Musica, copied at the beginning of every medieval Dominican Antiphonal, is at the top of this post. It is from the fourteenth-century Poissy Antiphonal.

His system for rhythm is presented in an accessible, albeit Latin, form in the Dominican Processionarium of 1949. The Dominican system of adapting psalm tones to the psalms found in that book was suppressed in 1965 [emphasis added] with the publication of the post-Vatican II Regulae Cantus in favor of the Benedictine method, although the Dominican melodies of the tones were left unchanged. But for all other chants, the thirteenth-century system continues in use today, in continuity with the living tradition of chant extending in an unbroken line back to the earliest days of the Order. The most important section of the Regulae Cantus for interpreting the chant is Section III, "De pausis et earum signis et proportione." I have adapted that section for use by choirs, and will present it in another post, but first singers need to know certain things.