And glad not to have invented Such comeliness, we are surrounded: A silence already filled with noises,
Fancy word time: "comeliness" means beauty, in a conventional sense (if there is one). So the speaker says no to inventing an artificial kind of beauty. Why artificial? Because the word "invented" suggests it's man-made, rather than natural. Think of Edward Scissorhands and all the landscaping he did. Everyone thought it was "comely" but it's also kind of artificial, you know, making a bush look like an elephant.
So what can we make of "such comeliness"? Maybe the speaker's referring to the comely beauty of the trees, or nature more generally. Maybe he's thinking about the ways such beauty can be manipulated by man, like Scissorhands.
So, even though the speaker and his partner didn't invent "such comeliness," they're still surrounded. Remember, colons are used to help introduce or list things. In this case that colon could be a substitute for the word "by." Again, Ashbery looks as if he's maintaining a specific kind of form with his use of parallelism via punctuation, rhymedcouplets, etc.
According to line 15, then, the speaker and his partner are surrounded by "a silence already filled with noises." See, it's not as confusing as it sounds, is it?
Let us make it less confusing for you, gang. First, start with the obvious. We have opposites going on here: "silence" and "noises." Why opposites? Opposites attract? The universe is governed by opposites? Is it chemical? Nature has opposites too, like the seasons. All sorts of things come to mind when we think of opposites.
We also have an example of a paradox here ("silence filled with noises"), meaning something that is a contradiction (putting opposites together). At first glance, a paradox doesn't make much sense, but in this context we (hopefully) start to get it a little more. Maybe this paradox is getting at the idea that the world is filled with opposites and, in order to understand one thing, you have to also understand its opposite. Nothing is ever so simple as a neat little definition standing all by itself without other things influencing it. There's always surrounding "noise."
Finally, we get some more enjambment at the end of this stanza, which leads us to the next stanza.