The poetic form of the dirge comes out of the early Christian Church when Christians would say morning prayers for, among others, the dead. But the poetic form came to mean any mournful song for the dead. (The dirge eventually evolved into a drinking song, but for our purposes that’s neither here nor there.) Whitman thought of his poems as songs, and “O Captain! My Captain!” is a piece that is closer to a song than any other written by Whitman.
Broken into three stanzas, each stanza contains a verse (in this case, these are the longer lines describing the arrival of the ship) and a chorus (here, the shorter lines describing the scene of the dead captain and the sailor that loves him). The verse sections are rhymed couplets, or two lines that finish with end rhymes and are related in their content.
Some of the couplets rhyme perfectly, like lines 1 and 2 (“done” and “won”) and lines 17 and 18 (“still” and “will”). Others like lines 9 and 10 have near, or slant, rhyme (“bells” and “trills”), meaning that the end words rhyme, but not so closely.
Why would Whitman mix up the rhymes this way? It wasn’t that he misplaced his rhyming dictionary. Remember that a dirge may be a song, but it’s a song for the dead. Sure, it may rhyme some of the time (see what we did there?), but it’s not a happy sing-a-long. It’s a sad song of remembrance, and these slant rhymes are there to remind us that it’s not all high-fives and good times going on here. The death that is the subject of the poem has upset the order of things, including the very rhymes themselves.
The last four lines in each stanza also represent a break in the pattern. They’re much shorter than the first four—about half as long, actually. Still, notice how if you treat lines 5 and 6 as one line and 7 and 8 as another line, then the rhyming couplet pattern continues throughout the entire poem. So if you were hearing the poem, you probably wouldn’t know that lines 5 through 8 were shorter than lines 1 through 4.
Visually, though, these lines of the chorus break off from the narrative, longer lines of the verses. They are shorter, choppier lines in which the speaker is introspective, reflecting on the loss of the captain. It’s as though his grief is responsible for the interrupted flow of these indented lines.
That choppiness carries over to the meter of the poem, as well. Mainly, the meter of the poem is in an iambic meter. What the heck is that? Well, an iamb is a two-syllable unit in which the first syllable doesn’t get much emphasis, but then the second one does. Say the word “belong” out loud (make sure nobody’s looking first). Notice that sound? Be-long. The second syllable gets the stress.
The same can be said for much, but not all, of this poem. Check it out:
our fear ful trip is done
Read it out loud, and you should hear da-DUM da-DUM da-DUM. That, friends, is the rhythm of the iamb. It propels you along in the poem with a purposeful beat, and can be found in the second half of lines 1, 9, and 17, as well as throughout lines 2, 10, and 18.
Notice, though, that this iambic rhythm repeats only in certain places of the poem. Each stanza is joined by keeping the same rhythmic structure, which makes sense because, after all, this is meant to evoke a song, right? Still, within each stanza there are other rhythms that compete with the iambs.
We’re talking mainly about the rare, exotic amphibrach here. Rarely seen in its natural environment, the amphibrach is a measure of rhythm that is an unstressed syllable, followed by a stressed syllable, followed by another unstressed syllable. For example, say the word “allowance” out loud. You should hear a rhythm like da-DUM-da. And you should also hear that same pattern in this poem, too. Check it:
O Captain! my Captain!
Notice how "Cap" is the only syllable that gets the stress in that phrase. Really, what Whitman’s does here is put not one, but two amphibrachs together. Right after this, we get the regular iambic pattern:
our fear ful trip is done
We also get amphibrachs at the end of lines 3, 4, 11, and 12 (check out the last three syllables of each of those lines). So, ol' Walt is mixing and matching his rhythms here. Again, why would he do that? Well, just like he varies his rhyme from perfect to slant, he’s using rhythmic variety to keep the reader on their toes. The most varied rhythmic patterns are saved for the indented chorus lines (no, not that kind of chorus line), where the speaker uses choppy lines to convey his sense of loss and grief. In short, this ain’t no sing-a-long. It’s a sad song that shifts around—both in terms of rhyme and meter—to remind the reader that there is something powerfully amiss.