Ever get a tune stuck in your head? We're willing to bet you have; some things just get caught on a loop in our brains. But what causes this ever-present ear worm? What makes something catchy?
Two things help: rhythm and rhyme. Over in "Form and Meter," we talk about how Randall's use of both rhyme and meter in this ballad form makes the poem stick in his reader's head. But that's not all the sound action that's taking place here.
We get, for example, moments of alliteration, as in line 14: "For I fear those guns will fire." All of those F sounds strung together almost mimic the force of a bullet leaving a gun. As well, we learn that the mother's eyes are "wet and wild" in line 26. The double W's catch our mind's ear (if you can picture that) and draw our attention to the mother's grief.
In addition to alliteration, we also get some assonance in the final stanza: "She clawed through bits of glass and brick,Then lifted out a shoe" (29-30). The short I in "bits," "brick," and "lifted" has the subtle effect of packing the same sound into our ear in a short, confined space. The sound is trapped, anxious—much like the unfortunate mother who is sifting through the rubble in search of her daughter. Sound, then, works in this poem in subtle ways but to a common effect: to reinforce the horrors of the violence described in the lines.