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

Decorative drop cap 'P'After these things, it is necessary to reveal by what signs the names of notes, their gravities, and their acuteness and extensions are perceived through lines and spaces. For every letter or seat disposed in a lineal or spatial place in the introductory work is called a key, since all notes are enclosed by those lines or spaces. But it is not established that it was necessary to declare every line and space with its own letters and keys, on account of the mutual crowding of the contiguous description. Wherefore, musicians deemed it appropriate to reveal all the strings of the introduction with fewer signs. For, as Aristotle pleases, it is done in vain through more what can be done through fewer. For they are accustomed to distinguish the grave, acute, and super-acute strings of the introduction by two signs, which are called keys. And the first sign indeed (to follow the beginnings of the ancients) is a single line, among four or five, filled with red color; when it occupies a lineal place, they ascribe it to C solfaut the note C; if it is described in a spatial place, it demonstrates F faut the note F grave. If it is described in a spatial place, it declares F faut acute. The second sign is a single line among four or five filled with a sea-green color; when this occupies a lineal place, they ascribe it to C solfaut; if it is described in a spatial place, it will indicate either C faut grave or C solfa super-acute, which is also frequented in Ambrosian notations. Add that the ancients observed that a single string marked with a celestial color and described in a spatial place was understood as B fa acute, but in a lineal place as B fa super-acute. And thus they easily distinguished all other voices and subsequent notes, to be considered through lines and spaces, in the grave and in the acute. But the more recent Gregorians, and those who again describe measurable songs, since they are accustomed to describe all lines with one and the same color, are accustomed to note the lineal key of F faut grave itself with three notes at the head of the line in this order in their writings:

Musicians

Aristotle

Musical notation diagram showing F-clef and notes

And they ascribe two square notes separately to the head of the C solfaut line in this manner:
Musical notation diagram showing C-clef
But B fa acute is declared by the description of the letter itself, as here:
Musical notation diagram showing B-flat

And in this order, the key is described where the first tetrachord of each hexachord is determined in the acute. Nor inappropriately did musicians, with one consent, ascribe a key to that note which would lead a semitone to its nearer grave. For the semitone itself is more friendly, and in proportion and delivery, it is more difficult by nature and art than a tone; hence it is in greater need of demonstration. Furthermore, voices which the notes declare are accustomed to be pronounced in three ways. In the first way, by solmizing, that is, by expressing the syllables and names of the voices, namely ut, re, mi, fa, sol, la, as here:

Musical notation diagram showing solmization syllables