Standing at the edge of a ditch at night, the speaker watches his own shadow slide across the water, and what begins as a simple observation turns, by the final stanza, into a small theory of how art is made. The poem is about the relationship between a person and the image he casts, and about the moment when something external, a patch of light on water, turns out to have come from inside.
The poem moves in a quiet sequence. First comes the shadow, silent on the ditch. Then the frogs, which sit "upon" it and are "blocked off from the stars," a detail that is oddly poignant: the speaker's own darkness shuts out the sky for the creatures below. The third stanza is the strangest and most important. The shadow "demands from my body / Unmoving images." The usual order is reversed. We expect a body to cast a shadow, but here the shadow gives orders, and what it wants is stillness. The speaker must hold himself rigid so that the image on the water can form. If we read the poem as being about making art, which the title invites us to do, this is a striking claim: the work asks the maker to freeze, to become a fixed thing so that something can be seen.
The imagery then shifts from stillness to motion. The shadow "skims the water like a huge / Violet-colored mosquito." The simile is unexpected in two ways. It makes the shadow insect-like, light and slightly sinister, and it adds color, violet, to what we assumed was plain darkness. That colored dusk fits the poem's title, since «Debussy» suggests music built from atmosphere and tint rather than from hard outlines. Whether the poem is meant to resemble a particular piece of music I can't say, but the mood it creates, hushed, shimmering, a little blurred, is easy to hear in that name.
The crickets then arrive. "A hundred crickets try to mine gold / From the light in the rushes." The verb "mine" is wonderfully physical. Crickets produce sound, so the metaphor quietly sets noise against light: the insects dig at the glow as if it were ore, hoping to extract something valuable. The word "try" matters too. They don't succeed, or at least we aren't told they do. It is hard not to see in this a picture of artists, or of anyone, working at something luminous and elusive with only the crude tools at hand.
The ending resolves the poem's puzzle. The light the crickets are digging at is "born in my heart / Upon the ditch, reflected." Until now, the light seemed to belong to the landscape, and the shadow to the speaker. The last stanza erases that division. The brightness in the rushes is the speaker's own inner light, projected outward and returned to him by the water. The ditch becomes a mirror, and the poem's apparently outward gaze turns out to have been inward all along.
Formally, the poem is spare. It is built in short stanzas, mostly two lines each, with no rhyme and no regular meter. The lines are plain and slightly halting, which suits a speaker holding himself still. Notice how often the word "upon" recurs, in the first, second, and last stanzas. It gives the poem a layered, stacked feeling: shadow upon water, frogs upon shadow, light upon the ditch. Everything rests on something else, and the whole structure is a series of reflections resting on a surface.
What makes the poem worth reading is how much it does with so little. In about a dozen lines it gives us a quiet scene, a strange reversal of power between body and shadow, and an image of creation that feels earned rather than announced. It never says "art" or "inspiration"; it lets a ditch, some frogs, and a hundred crickets make the argument. That restraint is the poem's charm, and the reason its final line lands with such a gentle jolt.