Sound-wise, the biggest thing going on in this poem is the end rhyme of the second and fourth lines in each stanza. Oh sure, you'll find some use of alliteration here ("Boy, and Barefoot," "stooping to secure"), but Dickinson's lines are so short that there are really not enough words to string together to create much of sensation with repeated beginning sounds.
Nope, the real action is with the rhyme, and rightly so in our opinion. After all, Dickinson was nodding (though not bowing) to the ballad form in her poetry (for more on that, check out "Form and Meter"), and rhyme was one of the ways that this form is held together.
Still, how tight is that rhyming ship? First off, only the half the lines in the poem rhyme, and some of the rhymes aren't even that exact. "Rides" and "is"? "Seen" and "on"? "Corn" and "Noon"? "Sun" and "gone"? Now, was Dickinson just a bad poet, or was something else going on here?
Well, one way to look at the sounds here is as slant rhymes. These are rhymes that are nearly, but not exactly, the same sounds, and—this is important—they are used for a reason. For Dickinson, her use of slant rhyme is totally in keeping with the way she takes out a syllable in the first and third lines of stanzas 3 through 6: she's subtly subverting the established, expected pattern. Think about it: in a poem that discusses the shock of expectations being dashed (that whip is actually a snake!), we think slant rhyme is really the best way, sonically-speaking, to get the idea across.