From the opening chapter of Boethius’s On Music (De institutione musica). He says why the “judgment of the ears” belongs among the four “disciplines of mathematics”, which later writers call the quadrivium. Boethius’s treatise was the standard Latin text on the theory of music through the Middle Ages.
Read in contextThe same can be said of the other sensibles, and most of all of the judgment of the ears, whose power so catches sounds that it not only takes judgment of them and knows their differences, but is also often delighted if the measures are sweet and fitted together, and pained if they strike the sense scattered and incoherent. Hence it comes about that, whereas there are four disciplines of mathematics, the others labour in the investigation of truth, but music is joined not only to speculation but also to morality. For nothing is so proper to humanity as to be relaxed by sweet measures and braced by contrary ones, and this does not confine itself to single pursuits or ages, but is spread through all pursuits; infants and youths and also old men are so naturally joined to musical measures by a certain spontaneous affection that there is no age at all that is separated from delight in a sweet song. Hence it can also be discerned that it was not said by Plato without reason that the soul of the world was joined together by musical concord. For when by that which is joined and fittingly fitted together in us we take in that which is aptly and fittingly joined in sounds, and are delighted by it, we know that we also ourselves are put together by the same likeness.