"The Voice" is one crazy-sounding poem, and that's what makes it awesome. There are a few interesting things about the poem's form, and we'll take them one at a time.
First up, we've got ABAB rhymes (also known as ballad rhymes) throughout the poem. Many, though not all, of the poem's rhymes are triple rhymes (in which the last three syllables of the lines rhyme with their partnering lines). For example:
Woman much missed, how you call to me, call to me,A
Saying that now you are not as you were B
When you had changed from the one who was all to me, A
But as at first, when our day was fair. B
The rhymes of lines 1 and 3, of "call to me" and "all to me" are triple rhymes. They sound a bit overdone to us, like the speaker is going over-the-top in his rhyming. Triple rhymes here sound artificial and fake (especially in rhymes like "listlessness and "wistlessness"), and this artificiality jives with one of the big questions of the poem: is the voice real or imagined?
In addition to all of the rhymes at the end of the lines, we've got tons of general sound-y-ness (yes, we just made that word up). There's alliteration in phrases such as "faltering forward" (13) and "thin through the thorn" (14). There's internal rhyme in words such as "you" and "view" (5), and assonance in words such as "mead" and "me" (10).
All of these repeated sounds that exceed the regular rhyme scheme make the poem incredibly dense. The repetitions make us feel like the speaker can't get out of the vicious cycle of grief that he's in. He keeps hearing voices, and he keeps reusing his own vocal patterns. There's no escape from sound in this poem.
The third important thing to know about the poem is its meter (or rhythm). "The Voice" is written in… quatrains (four-line stanzas) of dactylic tetrameter. Wait—don't run away scared! We promise we'll explain!
Dactylic tetrameter means that each line of the poem has four feet (that's the "tetra-" in "tetrameter"), and that each of the poem's feet (which is like a unit of rhythm) is a dactyl. A dactyl is a foot that's made up of a stressed syllable followed by two unstressed syllables. For example, if you say "penalty" out loud, you'll hear a dactyl: DA dum dum. So, when we scan (or figure out the meter of) the first stanza of the poem, we get this pattern:
Woman much missed, how you call to me, call to me
Saying that now you are not as you were
When you had changed from the one who wasall to me,
But as at first, when our day was fair.
The effect of this uncommon meter is a waltzing, lilting feel. It makes us a little dizzy, so don't worry if you're feeling dizzy, too. And what is especially dizzying is that the even-numbered lines are two or three syllables shorter than the odd-numbered lines. The unevenness makes us feeling like we're teetering on a ledge, about to fall over. And in case you haven't noticed, we're in the exact same predicament as the speaker. We're unsure and we've lost our footing—and maybe even our connection to reality. The dizzying form forces us into the position of the speaker. Yikes!
The last important formal thing to think about with "The Voice" is the final stanza of the poem, which shrinks, quite literally. Hardy condenses his weirdo form into something even weirder as he breaks his own patterns. It's almost like the speaker of the poem gives up in the final lines, and he surrenders to the natural sounds of the words, instead of keeping to the strict meter. We read this last stanza as a kind of surrender (both in terms of form and content) to the mysterious voice. The speaker's rhythms no longer matter—it's all about the ghostly voice.