Music of the spheres, musica mundana, is the music that the spheres make in their rotations around the earth. (That’s why, incidentally, the first person to put forth a coherent theory of musical intervals was Ptolemy. Just like the heavens could be described in perfect ratios, so could music.) C. S. Lewis explains in The Discarded Image that, like Dante in Paradiso, “if our ears were opened we should perceive” that which makes the universe “lighted, warmed, and resonant with music.” (Discarded Image, 112)
The problem comes in the motion of the spheres. It must, to an Aristotelian mind, come from something that moves but is not itself in motion (hence Aquinas’ cosmological argument in ST 1.2.3). God must himself cause the Primum Mobile to rotate, and then, like Timaeus’ demiurge, PM passes on what it has received from the ineffable God to lower spheres. The problem for the Medieval Model, similarly in Timaeus, is that God himself can’t be soiled with this act of moving or creating. “But we must not imagine Him moving things by any positive action, for that would be to attribute some kind of motion to Himself and we should then not have reached an utterly unmoving Mover.” (113)
So, attempting to “save the phenomena”, Aristotle postulates that God “moves as beloved.” C. S. Lewis explains, “He moves other things, that is, as an object of desire moves those who desire it. The Primum Mobile is moved by its love for God, and, being moved, communicates motion to the rest of the universe.” (113) This is what Dante means when he ends the Divine Comedy with “the love that moves the Sun and the other stars” (114).
It’s a beautiful thought, but Lewis points out that this is not the typical sense in which we refer to the “love of God”. Usually we mean his love for creation, but in this case, we’re referring to creation’s love of him. This isn’t necessarily a point of tension, but the general idea that the ineffable God couldn’t be involved directly in the act of creation is precisely the bone of contention that is picked in the battle between Neo-Platonism and Christianity.
Interestingly, in Tolkien’s play on the idea of musica mundana, he resolves the tension by a sort of “we love God for he loved us first” creation story. Of course, it still comes back to music.
And it came to pass that Ilúvatar called together all the Ainur and declared to them a mighty theme, unfolding to them things greater and more wonderful than he had yet revealed; and the glory of its beginning and the splendour of its end amazed the Ainur, so that they bowed before Ilúvatar and were silent. Then Ilúvatar said to them: “Of the theme that I have declared to you, I will now that ye make in harmony together a Great Music. And since I have kindled you with the Flame Imperishable, ye shall show forth your powers in adorning this theme, each with his own thoughts and devices, if he will. But I will sit and hearken, and be glad that through you great beauty has been wakened into song.” (J. R. R. Tolkien, The Silmarillion, 15)
Here you have many of the elements involved in the music of the spheres, but the theme is declared to them directly by Ilúvatar. He wills it and he has kindled in his angels the Flame Imperishable, much more like the theistic conception than the deistic conception, but at the same time he does delegate, much like the ineffable God of the Medieval Model. This God, however, “will sit and hearken” and is glad “that through you great beauty has been wakened into song.”
Lewis points out that the Medieval Model is hierarchical according to the devolutionary principle: anything derived is necessarily less perfect than the original from which it was derived. That is why man and matter are at the bottom of the Hellenistic totem pole (ha, ha). Every middle-man creator that has created has lost more and more of that original ineffable God, and man and matter are the last to be created. Tolkien’s universe, though, is hierarchical still, but not according to the devolutionary principle. The theme is first explained by Ilúvatar, but is inevitably harmonized upon and adorned by the Ainur, “each with his own thoughts and devices.” It is through them that great beauty has been wakened into song. Just as the boss who takes a personal interest ends up getting better work out of his employees, Ilúvatar is intimately involved in the music making—not distant—and so, through his Ainur, the music doesn’t devolve but evolves. Instead of corrupting the original, the Ainur crown it.