Practica Musicae utriusque cantus, excellentis Franchini Gaffori Laudensis quatuor libris modulatissima

Which method of pronunciation is indeed taught as a law to be placed before children when they are initiated. In the second way, by emitting only the sounds and voices, omitting the letters, syllables, and words entirely, which the practiced cantor easily pursues in this way. In the third way, by pronouncing whatever words—such as antiphons and responsories—and the words of the songs themselves, written below the notes themselves. To these, as to the end, the clerics lead the chosen modulations, as here:

Musical staff showing a rising and falling scale pattern with square notation.

But the notes themselves declare the pronunciation of syllables in this order. For when "re" is sharper than "ut" by a tone, its sound is to be raised by the interval of that tone, and "ut", conversely, is to be depressed from "re" by the interval of a tone in this way:

Musical staff showing a rising and falling interval pattern.

Likewise, the sound of the note "mi" raises from "re" by a tone, and "re" is depressed from "mi" by the interval of the same tone, which is considered with these notes:

Musical staff showing a rising and falling interval pattern.

The "fa" sound is intended from "mi" by the interval of a minor semitone, and "mi" is remitted from "fa" by the interval of the same semitone into the grave, as here:

Musical staff showing a rising and falling interval pattern.

The "sol" syllable, however, intends the sound above "fa" by the interval of a tone, and "fa" is remitted from "sol" by the interval of the same tone into gravity, which these notes declare:

Musical staff showing a rising and falling interval pattern.

The sound of the syllable "la" is sharper than that which is "sol" by the interval of a tone, and "sol" is depressed from "la" by the same tone, which is easily perceived by the arrangement of these notes:

Musical staff showing a rising and falling interval pattern.

Again, "mi" is tended from "ut" in the acute by the interval of a ditone, and "ut" is depressed from "mi" by the same distance into the grave, which happens in two ways: that is, composite and simple. Composite, when it is circumscribed by the interval of two tones with two extreme limits, with a middle term interwritten, as here:

Musical staff showing a rising and falling interval pattern.

Incomposite, however, when the distance of two tones is closed by two extreme limits only, with no middle term interwritten, which is clearly perceived by these notes. Boethius and Ptolemy assigned this to enharmonic tetrachords as naturally harmonious:

Musical staff showing a rising and falling interval pattern.

Boethius
Ptolemy