Harmony and music: the cosmos as a chord

For the ancients and for the people of the Renaissance, harmony was not merely a matter of pleasant sounds. It was the law that held the cosmos, the soul and the body together. In the second book of the De occulta philosophia, after numbers and figures, Agrippa devotes several chapters to music and harmony, regarded as a branch of mathematics and therefore part of celestial magic. Sound, for him, is number made sensible, and for that very reason it can connect the earthly world with that of the stars.

Pythagoras and the music of the spheres

At the centre stands the Pythagorean tradition. A famous legend, told by Nicomachus of Gerasa and handed down by Boethius in De institutione musica, relates that Pythagoras, passing a blacksmith's shop, noticed that the hammers produced consonant chords when their weights stood in simple ratios. From that discovery, according to the story, came the proportions of the octave, the fifth and the fourth, the foundation of ancient music theory.

Plato, in the myth of Er that closes the Republic, had imagined the celestial spheres each surmounted by a siren singing a single note, and Cicero, in the Dream of Scipio, had described the sound produced by the motion of the heavens, too powerful for the human ear to perceive. Agrippa takes up these images and assigns to each planet a musical interval and character, following schemes already discussed by medieval theorists.

Music and the soul

If heaven is harmony, so too is the human soul, because according to the Timaeus it is built from the same proportions. This, Agrippa explains, is why music acts on us so deeply: the spirit, airy and mobile, receives the motion of sound and passes it on to the soul, awakening its correspondences with the heavens. It is a theory that Ficino had developed in the De vita, where he described song as a means of attuning the spirit to the stars.

In support of this idea Agrippa gathers famous examples. The Bible tells that David soothed with his harp the evil spirit that tormented King Saul. Greek tradition credited the musician Timotheus with the power to rouse and calm Alexander the Great with the different musical modes. Of Pythagoras it was told that he had calmed a young man seized by rage by changing a player's melody. These are ancient stories, presented as evidence of the power of sound.

Proportion and the harmony of the body

Harmony, finally, concerns not only sounds but also proportions. Agrippa extends the concept to the human body, whose measurements were held to be governed by the same ratios that rule music and the cosmos. This idea prepares the chapters on geometric figures and on human proportions, illustrated in the 1533 edition, and links musical reflection to the doctrine of the microcosm.

The theory of universal harmony had a long life. In 1619 Johannes Kepler published Harmonices mundi, in which he still sought musical ratios in the motions of the planets, though on new astronomical foundations. Agrippa's pages belong to that same tradition and remind us how long music, mathematics and cosmology were considered parts of a single science. As late as 1650 the Jesuit Athanasius Kircher, in his Musurgia universalis, would take up many of these ideas.