The poem opens with a brief focus on its key object: the buzz saw. From the beginning, the buzz saw "snarls" and "rattles," hinting at the terrible tragedy that is to come. "Snarled" also implies anger and aggression, and accordingly is part of the way that the poem personifies the buzz saw—as though the saw's waiting for its moment to strike. The alliteration of "saw" and "snarled" combines with the /z/ sound in "buzz" to create a harsh opening sound (this is also known as sibilance). That said, the poem is careful not to overdo the menace of the saw: it does make a harsh sound, but that's only because it needs to in order to fulfill its function of cutting wood.
The consonance of /d/ sounds that run throughout the first line make the line itself "rattle" with that particular sound, as though hinting at the power of the saw and the potential for its human users to lose control. This /d/ sound is emphasized through alliteration and consonance in the second line too. Here are the first two lines:
The buzz saw snarled and rattled in the yard
And made dust and dropped stove-length sticks of wood,
But as mentioned above, the poem doesn't go all out on setting up the saw as some kind of inanimate villain. The wood that gets chopped results in "Sweet-scented stuff" (more alliteration) carried on the "breeze." The mention of "breeze" opens up the poem's idyllic description of the setting: rural Vermont.
Lines 4-6 are pure pastoral poetry (that is, poetry that depicts the pleasures of rural life) deliberately luring the reader into a false sense of security after the vague opening threat of the buzz saw. Contrasting with the opening three lines, the poem uses much gentler /n/ consonance in these lines, also part of the way the first section disarms the reader:
And from there those that lifted eyes could count
Five mountain ranges one behind the other
Under the sunset far into Vermont.
The enjambment between the three lines here creates a sense of bountiful beauty, the long sentence length conveying the way that this natural beauty seems to stretch as far as the eye can —indeed, five mountain ranges are visible all at once "under the sunset."
It's also worth noting that, for all the alliteration and consonance, the poem sounds distinctly prose-like too. The vocabulary in particular is deliberately plain, and the rhetorical devices are used subtly. This is in part about luring the reader into the false sense of security mentioned above, but it's also designed to paint the scene as relatively mundane and everyday. In other words, the poem tries to portray a typical day in this family's life—which will help create the element of surprise with what follows.