De institutione musica I.2: Tres esse musicas; in quo de vi musicae.
To one beginning, then, to discourse on music, this must meanwhile seem to be said: how many kinds of music we know to have been comprehended by its students. There are three. The first is the music of the world, the second human, the third that which is set in certain instruments, as in the cithara or the pipes and the others that serve song. And first, that which is the music of the world is chiefly to be perceived in those things which are seen in the heaven itself, or in the framework of the elements, or in the variety of the seasons. For how can it be that so swift a machine of the heaven is moved in silent and quiet course? Even if that sound does not reach our ears, which must happen for many reasons, so very swift a motion of such great bodies cannot yet cause no sounds at all, especially as the courses of the stars are joined by such a fitting together that nothing so compacted, nothing so joined can be understood. For some are borne higher, others lower, and all revolve with an equal impulse, so that through unequal inequalities a fixed order of the courses is led. Hence a fixed order of melody cannot be absent from this heavenly revolution. Now if a certain harmony did not join the diversities and contrary powers of the four elements, how could they come together into one body and machine? But all this diversity so produces both the variety of the seasons and of fruits as yet to make one body of the year. Hence if you were to pluck out any of these, which supply so great a variety to things, in mind and thought, all would perish and, so to speak, keep nothing consonant. And as in the low strings the measure of the voice is such that gravity does not descend to silence, and in the high strings that measure of acuteness is kept lest the strings, stretched too tight, break in the thinness of the voice, but the whole is concordant and agreeing with itself: so also in the music of the world we see that nothing can be so excessive as to dissolve the other by its own excess. But whatever it is, it either brings its own fruits or helps others to bring them. For what winter binds, spring loosens, summer parches, autumn ripens, and the seasons in turn either bring their own fruits themselves or supply others to bring them; of which we must discuss more carefully later. Human music anyone understands who descends into himself. For what is it that mingles that incorporeal vivacity of reason with the body, if not a certain fitting together and tempering, as of low and high voices, making as it were one consonance? What else joins the parts of the soul itself among themselves, which, as Aristotle holds, is joined of the rational and the irrational? What is it that mingles the elements of the body, or holds the parts together to one another in a fixed fitting? But of this also I shall speak later. The third is the music said to consist in certain instruments. This is administered either by tension, as with strings, or by breath, as with pipes, or those that are moved by water, or by some striking, as in those which are struck on certain hollow brazen vessels, and from which different sounds are produced. Of this music of instruments it seems we must treat first in this work. But enough of the proem. Now we must discourse on the elements of music themselves.