A Dust of Syllables

I took a walk in the woods last week. The snow was thick and rather wet that day, and as, near the end of my walk, I stopped my crunching footsteps to listen, I heard crows cawing to each other, a repeating music, punctuated occasionally by the plop of wet snow off a branch, and then by a cascade of flakes following. There in the stillness, a tiny poem of Frost's came into my head:

Manuscript copy of "Dust of Snow" signed by Frost

In the quiet whiteness of the snow, with no distractions or hurry, it came to me syllable by slow syllable, so precisely balanced between them that I noticed again how few syllables there are. And in particular, I noticed how few EXTRA syllables there are—none at all, until the fourth line, halfway through the poem:
The way a crow
shook down on me
the dust of snow
from a hemlock tree
That extra syllable ("from"), hit me, among the trees, as a dust of snow itself, falling from the line above it, down through the poem.
And, just as real snow is likely to hit at least another branch on its way down, so the dust of this syllabic snow impacts the line below it:
Has given my heart
before the poem remembers and rights itself:
a change of mood
and saved one part
and here the self-consciousnessness of memory comes back in, and the branch shakes a final time:
of a day I had rued.
The exact tone of that last line has been a mystery to me as long as I have known this poem. Last week, I realized that these may be the most melancholy two anapests I have ever read. They dwell too long on the gift of the single anapest, and so they taint it, unnecessarily. The gift, examined too long, turns sour. And yet the poem retains its freedom; the syllable "had" indicates, so quickly it is almost a subliminal suggestion, that the rueing is over, and with the lightness of "rued" as opposed to "mood," the poem ends in a syllable of possibility, the branch freed of the weight of its snow, and open to be moved again.