The Twelve-Stringed Lyre

How from the connection of the diatessaron: the interval of a perfect fourth and the diapente: the interval of a perfect fifth, twenty-four species of the diapason: the interval of an octave are made, of which twelve are rejected and twelve are accepted, Chapter III.
How from twelve species of the octave only seven are produced, Chapter IIII.
What our age seems to have changed in these modes, and to what extent this is permitted to be done, Chapter V.
That it is necessary to establish twelve modes, since our eighth mode has been correctly separated from the others, Chapter VI.
On the order of the modes and their naming, Chapter VII.
On the low pitch original: "gravitate" and high pitch original: "acumine" of the strings, and their naming according to those qualities, Chapter VIII.
In what way the modes are to be taken, and which is the first string of all the modes, Chapter IX.
Several passages from authors discussed which seem contrary to the precepts we have handed down so far, Chapter X.
On the mutual changing or permutation of the modes, Chapter XI.
Why the number seven is so frequent among authors in musical matters, Chapter XII.
Two opinions on the sound in the heavens A reference to the "Music of the Spheres," the ancient theory that planets produced harmonious sounds, and therein passages from Cicero and Pliny Pliny the Elder and Cicero were primary Roman sources for the idea of celestial harmony are examined, Chapter XIII.
What is to be understood by the nine Muses, Chapter XIIII.
A brief summary original: "Anacephalaeosis," a Greek term for a recapitulation or summary concerning the division of the modes, Chapter XV.
On the first species of the octave and its two modes, Chapter XVI.
On the Aeolian mode, Chapter XVII.
On the second species of the octave and its one proper mode, Chapter XVIII.
On the third species of the octave and its two modes, Chapter XIX.
On the Ionian or Iastian mode, Chapter XX.
On the fourth species of the octave and its two modes, Chapter XXI.
On the Hypomixolydian or Hyperiastian mode, Chapter XXII.
On the fifth species of the octave and its two modes, Chapter XXIII.
On the Hypoaeolian mode, Chapter XXIV.
On the sixth species of the octave and its one proper mode, Chapter XXV.
On the seventh species of the octave and its two modes, Chapter XXVI.
On the Hypoionian mode, Chapter XXVII.
On the connection of the modes and their sharing via the fifth original: "diapente", Chapter XXVIII.
On the 1st connection, which is from the 1st and 4th species of the octave, Chapter XXIX.
On the 2nd connection, which is from the 2nd and 5th species of the octave, Chapter XXX.
On the 3rd connection, which is from the 3rd and 6th species of the octave, Chapter XXXI.
On the 4th connection, which is from the 4th and 7th species of the octave, Chapter XXXII.
On the 5th connection, which is from the 5th and 8th species of the octave, Chapter XXXIII.
On the 6th connection, which is from the 6th and 9th species of the octave, Chapter XXXIIII.
On the 7th connection, which is from the 7th and 10th species of the octave, Chapter XXXV.
That the modes are best known by the mediation of the octave, which is done through the consonances of the fifth and the fourth, Chapter XXXVI.