I'm not going to write much about this chapter, because while I think it adds a lot to the story, it also seems to be fairly self-descriptive.
Furthermore, I think it follows exactly in line with nearly everything that I've written before. The Marble Lady is like a muse, which according to classical mythology really is an embodiment of artistic inspiration. This is no surprise to me because it is clear to me that women (to put it generally) are the main inspiration for most of the things done by men. Why is the Mona Lisa, one of Leonardo's most famous paintings, a simple portrait of a woman?
But that's a much longer and more important subject than I really want to (or am able to) address. What I will say is that it doesn't surprise me at all because I feel the exact same impulses as MacDonald (through his protagonist Anodos) or Leonardo. Beauty itself, whether that be natural beauty or the physical beauty seen in people, is an inspirational force.
To make one simple comment (in case anyone doesn't notice this), Anodos's song is a description of the Marble Lady's physical appearance, rising from her feet up to her forehead and hair. This song is supposed to match her persistent unveiling as the shadow is lifted off of her.
For the consequences of this song, we read on to Chapter 16.