In general, the rhyme scheme Coleridge used for “The Rime of the Ancient Mariner” follows the traditional pattern found in ballads. Ballads typically feature an ABCB rhyme scheme, where the first and third lines don’t rhyme, but the second and fourth lines do. As is also often the case in ballads, Coleridge frequently uses internal rhyme in the opening line of a stanza. This use of internal rhyme, combined with the alternation between nonrhyming and rhyming lines, is particularly helpful to those who are listening to a ballad. The pattern establishes a repeating structure that organizes each stanza into a single unit that’s easy for the ear to hear. For an example that encapsulates the ballad standard, consider the following stanza from early in the poem (lines 21–24):

     “The ship was cheered, the harbour cleared,
     Merrily did we drop
     Below the kirk, below the hill,
     Below the lighthouse top.”

Just as is to be expected in a traditional ballad stanza, the opening line features an internal rhyme (“cheered”/“cleared”). The only other rhyme in the stanza then comes as an end rhyme between the final syllables of the second and fourth lines (“drop”/“top”).

Though Coleridge generally follows this ABCB pattern, it’s important to note that he deviates from it quite often. The deviations typically arise in the stanzas with more than four lines. For example, this six-line stanza from Part 2 uses an ABCBDB scheme (lines 97–102):

     Nor dim nor red, like God's own head,
     The glorious Sun uprist:
     Then all averred, I had killed the bird
     That brought the fog and mist.
     'Twas right, said they, such birds to slay,
     That bring the fog and mist.

An even more extreme variation appears this nine-line stanza from Part 3 (lines 203–211):

     We listened and looked sideways up!
     Fear at my heart, as at a cup,
     My life-blood seemed to
sip!
     The stars were dim, and thick the
night,
     The steersman's face by his lamp gleamed
white;
     From the sails the dew did
drip
     Till clomb above the eastern bar
     The hornèd Moon, with one bright star
     Within the nether
tip.

This audacious stanza follows an entirely original rhyme scheme: AABCCBDDB. In this particular case, it’s important to pay attention the relation between form and content. This unusually long stanza finds the Mariner in an emotionally excited state, just before all the other sailors on his ship mysteriously drop dead. Coleridge uses a longer stanza, which he pairs with a more sustained rhyme scheme, to reflect the Mariner’s emotional paralysis at a crucial moment in the poem. Others variations throughout the poem similarly reflect the narrator’s shifting emotional state.