A chorus of smiles, a winter morning. Placed in a puzzling light, and moving,
Don't look now, but there's more parallelism too here, going back to lines 15 and continuing to lines 16 and 17 with the same beginning structure: "A silence […]," "A canvas […]," and "A chorus […]." Check out "Form and Meter" for more on all these parallel shenanigans.
So what emerges from that canvas? Why, it's a chorus of smiles. Of course it is. It looks like we're working with a set of images in line 17 that's getting at the common sorts of things we experience during the course of our lives.
But why a "chorus of smiles"? It's a strange sort of imagery that seems to be bridging the gap between sound ("chorus") and image ("smiles"). Again, things are working together here.
A "winter morning" seems to be doing the same sort of thing because when we imagine winter mornings we often think of things looking and sounding rather quiet, right? Winter is a whole lot less noisy than summer, for instance. People tend to stay put indoors and the snow acts as a pretty good muffler.
So Ashbery seems to be working with lots of different ideas in these images. Some relate to sound while others relate to image.
Notice that line 17 ends with a period? We should take a minute to kind of let those images settle in our minds and think about the things we associate with them.
Line 18 tells us it's okay to be confused. (Gee, that's a relief.) "Placed in a puzzling light, and moving" seems to really drive the point home that being confused by what we see, feel, and hear is all part of the experience.
But let's look even closer at line 18. We might consider the idea that the more we try to make sense of something, the more it seems to "move" out of our grasp. Meaning's a slippery little devil that doesn't want to be put into a box.
And much of our understanding of experiences, especially relationships, works in a similar way. We just can't get why Sandy doesn't love us like we love her, or why Bobby always gets the girl even though he's a total bum? The more we try to figure these puzzles out, the more miserable and confused we get.