In the absence of any musical score, training in the art of singing is acquired through regular and direct practice during the liturgical office, when the liturgical action places the apprentice in the best conditions for concentration and memorization. The cantors are supervised by a master who teaches them the correct pronunciation of Latin with its proper accentuation, as well as the science of music: modes, melodic and rhythmic formulas, intonations, and cadences.
The art of the cantor is clearly distinct from simple choral psalmody — flowing and sung at half-voice — as well as from the murmurare, in which each person recites the psalm for themselves, yet together with the others. The cantor is responsible for the cantilena, which is not merely a “cantilena” in the modern sense, but encompasses the entire repertoire, the art of singing, and the emotional effect of the music on the sensibility. The cantor derives his noble status from Saint Augustine (354–430) and Isidore of Seville (570–636), whose works were devoutly read, copied, and commented upon. Rules and councils laid down statutes concerning chant.

Here are the famous words of Isidore of Seville (570–636) on cantors: “It is important that the cantor be distinguished by his voice and his art, so as to draw the souls of the listeners by the charm of sweet pleasure. His voice should not be harsh or dull, but resonant; not hoarse but pleasant and melodious; not false but clear and pure, capable of sustaining the high notes of the register. It should produce a sonority and a melodic line in keeping with holy religion, avoiding the resonance of a tragedian’s art. On the contrary, it should manifest in its musical arrangement a Christian simplicity that does not evoke the mimicry of the poet-musician or theatrical art, but which stirs a deeper emotion in the listeners.” (De ecclesiasticis officiis, Book II, Chapter 12).
Nothing could be further from the whispered Gregorian chant than the Carolingian cantor depicted on an ivory plaque preserved in Cambridge. With his sternum raised and his gesture of opening, he sings from memory at full voice. The ideal voice is sonora: powerful and singing. Other texts speak of vox clara, vox strenua, emphasizing a strong yet easy voice, quasi tuba (resounding like a clarion call). Raban Maur (780–856) even writes: vox plena succo virili — a voice full of virile sap. The vox liquida is frank and clear: it delivers the exact intervals to the ear and the precise articulation of consonants. Vox acuta refers to the voice deployed with brilliance in the high register. Vox suavis remains the most frequently used expression. The effect of suavitas arises from the union of the cantor’s sapientia (wisdom) and peritia (technical skill) — from what belongs to taste and what belongs to performance. The vocal deployment through precise intervals pleasing to the ear is called modulatio. Finally, the chant conveys the intention of the text and its nuances; it transmits its emotion. If theatrical art is rejected, is it not because the cantor’s art constantly brushes against it? For he is commanded to sing differentialiter: modo indicantis, modo historici, modo dolentis, increpandis, miserantis…
This vox sola imprints the sung words into the soul of the listener, triggering an intense pleasure akin to that experienced when tasting or savoring something exquisite. The cantor’s voice seduces and gently leads the listener to a delectatio that lowers barriers and dissolves inner resistances.
Amalar of Metz (775–850) compares the lead cantor to a ploughman. His companions, like oxen, pull the plough: “He ploughs who, with the ploughshare of compunctio (which wounds the heart), cleaves the hearts; there is no doubt that, through the charm of modulation, hearts that are still carnal are split open and opened as if by the blade, in loud praise and tears.” (Liber officialis, Book III, Chapter 11).
A current of austerity, embodied by Agobard, Bishop of Lyon (c. 779–840), considered the development of singing in the sanctuary useless and dangerous. In contrast, Amalar opens up a grand horizon for chant: that of building a form of sociality close to the one Charlemagne dreamed of constructing when he had The City of God by Saint Augustine read to him before falling asleep.
The Step-by-Step Sequence (06:11) (in French)
00:00 - 1. The Sound
01:28 - 2. Space and Time
03:30 - 3. Musical Writing
04:48 - 4. The trope