Rounds gives us a quiet scene at the end of the day: an old harbor, the sun going down, and the shapes of trees along a sandy shore. The opening lines set up a puzzle. "Darkest black" and "whitest gold" push each color to an extreme, and the contradictions feel right for dusk, when light and dark blur together. Then the poem shows us what that looks like. The sun "bleeds gold" across the water, a slightly painful image, while the trees become flat black shapes, as if someone has painted them in.
The speaker seems to be watching alone, and the poem never says outright how they feel. But the mood is calm, a little wistful, and lonely. The harbor is "forgotten," and the final line makes the point plainly: "No one sings with it." The dusk performs for nobody, and the speaker's quiet attention may be the only audience it has. That makes the moment feel intimate, almost secret.