Rhyme, like rhythm, sets up an expectation and then fulfills it.  In the following light verse, "The Hardship of Accounting," by Robert Frost, we see how rhyme works first to capture interest, then to arouse expectation, satisfy it,and secure meaning in a memorable way.

Never ask of money spent
Where the spender thinks it went.
Nobody was ever meant
To remember or invent
What he did with every cent

Never ask of money spent
Where the spender thinks it went.
Nobody was ever asked
To remember or make up
What he did with every penny.

The pleasures of fulfilled expectation need not be simple.  Rhythm establishes a beat and may then expressively skip or misplace it.   Rhyme announces a consonant-vowel pattern and then echoes it exactly--or on a slant.  We should not make the mistake of identifying music solely with harmony.  As the great Canadian critic Northrop Frye once pointed out, music is even more dependent on discord than on harmony.  The most truly musical poets, Frye says, are those who know how to create tensions and not merely soothing monotonies of sound.  Varieties of rhyme, other patterns of word sound, and cacophonous as well as euphonious combinations of sound contribute to a poem's music.

TYPES OF RHYME

An exact rhyme is a sound identity following an initial difference. A word that is an exact homophone of a prior word, or a repetition of it, does  not rhyme with its predecessor because there is no difference.    Die and dye are not exact rhymes, but die and fly are.  Note that rhyme is based on the word's sound, not its spelling, though sometimes the sound has changed in modern times from what it once was.  Such formerly exact rhymes can be called "eye rhymes," or they may be varieties of slant or half rhyme.  Rhymes that involve single syllables (fuse/use, invent/content) are called masculine rhymes; rhymes that involve two or more are called feminine rhymes (master/faster; hilly/silly; portentous/prevent us; quivering/shivering); some prefer to call rhymes involving more than two syllables "multiple" rather than "feminine."  Feminine, and especially multiple, rhymes, since they tend toward overemphasis and suggest an indulgence in the pleasure of sound for its own sake, are often found in light or humorous verse.  But feminine rhymes are often used seriously as well. Note the italicized examples from W.D. Snodgrass's "Mementos ii":

How proud I was to gain you!
No one could warn
me of the pride or of
the fear my love might stain you
that would turn your face to scorn--
of the fear you could not love
that would tease and whine and haunt you
till all that made me want you
would gall you like a crown
of flowering thorn.
My love hung like a gown
of lead that pulled you down.
 

W may also use the above example to consider how all kinds of  rhyme work to stress the poet's most important ideas and at the same time to assist in the movement of the ideas through the poem.  The final couplet of the stanza, for instance, not only by its powerful image of love as a "gown of lead" but also by the rhyming of "down" and "gown," draws attention to the image of a sad weight.  Another rhyming word,"crown," in the simile "crown of (flowering) thorn" is attached by its sound to the same image.  "Thorn" itself rhymes with "warn" and "scorn," all suggesting painful disaster.  Even "of," not itself a powerful word, links "pride" and "fear" to "love," with which it rhymes.

Rhymes, then, especially if not all the lines in the poem are rhymed, are used to stress important ideas  or to create units within the poem.  For instance, rhymes were often used at the ends of scenes or acts in blank verse plays, to indicate the conclusion of a unit of action.  All schemes, or figures of sound, have these two functions: emphasis, and unit-creation.  End-rhymes are particularly strong markers in many poems because they reinforce or function in tension with another organizing device, the line end.  Line ends are important even in unrhymed verse because they stand out clearly and compel some kind of pause that affects the cadence.

In addition to end-rhymes, the poet may also use medial  (internal) rhymes.  Internal rhyme occurs anywhere within a line, as in "And the bay was WHITE with silent LIGHT."

Compared to languages like French and Italian, English is not rich in exact rhyming possibilities.  There are many common English words for which there is no exact rhyme: for example, circle, desert, month, wisdom.  Weak poets may succumb to hackneyed rhymes like moon/June/tune, or mispronounce words, or (worse yet) distort meaning to fit whatever rhymes come to mind.  Strong poets come up with fresh solutions, for example, renewing an old rhyme in a next context.  Or they invent a new type of rhyme.

One significant adaptation to the limited reservoir of exact rhymes in English is the use of slant rhyme (also called near-,half-, oblique-, or off-rhyme).  This kind of rhyme usually has the same final consonant, but a different final vowel (or the same final vowel but a different final consonant).  Here is a beautiful example from Walt Whitman, who did not often use rhyme:

Weapon, shapely, naked, wan,
Head from the mother's bowels drawn,
Wooded flesh and metal bone, limb only one, and lip only one,
Gray-blue leaf by red-heat grown, helve produced from a little seed sown,
Resting the grass amid and upon,
To be leaned and to lean on.

OTHER PATTERNS OF WORD SOUND

There are other instruments in the poetic orchestra which are very similar to rhyme, in that the involve the repetition of vowel and consonantpatterns.  One of these is alliteration--the repetition of the same consonant sound in a sequence of words.  If the sound occurs at the beginnings of words, it is called "initial alliteration," or just alliteration for short, since this is the most common and powerful form of alliteration.  But if the repeated consonant occurs in various positions within the word, we may call it medial alliteration or simply consonance.  An example of initial alliteration appears in the first two lines of Robert Frost's "Nothing Gold Can Stay":

Nature's first green is gold,
Her hardest hue to hold.

A sequence of repeated vowel sounds is called assonance.  In Hart Crane's "The Hurricane," this device is among a number of methods the poet uses to try to give the reader a sense of the storm as opposed to a commentary on it:

Lo, Lord, Thou ridest!
Lord, Lord, Thy swifting heart

Naught stayeth, naught now bideth                                bideth = abideth = endures
But is smithereened apart!

Ay! Scripture flee'th stone!                                            flee'th = flayeth
Milk-bright, Thy chisel wind

Rescindeth flesh from bone
To quivering whittlings thinned--

Swept--whistling straw!  Battered,
Lord, e'en boulders now out-leap

Rock sockets, levin-lathered!                                        levin-lathered = whipped by lightning
Nor, Lord, may worm out-deep

Thy drum's gambade, its plunge abscond!                       gambade = leap   abscond = escape
Lord God, while summits crashing

Whip sea-kelp screaming on blond
Sky-seethe, high heaven dashing--

Thou ridest to the door, Lord!
Thou bidest wall nor floor, Lord!

The cumulative effect of the short i sounds, especially in "quivering whittlings thinned," is to indicate the shrillness and sharp, high pitch of the fierce winds.  The imitative effects of these word sounds, however, is greatly dependent on their meaning, unlike those words that have a direct imitative effect, onomatopoetic words (the name of the device is onomatopoeia).

That the poet has at his command a wide and subtle range of means for imitating sound, going far beyond the onomatopetic hiss, buzz, gurgle, and mumble, is obvious.  Consider this passage from Delmore Schwartz' "A Small Score."  The "score" is for the concert that the birds give as dawn breaks:

Bubble, little,
Whistle, pretty,
Trickle, whittle,
Lipping and dripping
. . .
Thus, thus, the little birds sang in charming disorder and full chorus
To greet gravely, sweetly, and most meetly
The blaze of majesty soaring in great oars,
And their twinkling and carrolling grew more and more
    sure as they saw the great roar of awe
        arising surely all over the great blue
            bay above them.

Sound patterns of verse also assist in rendering motion.  Consider the following sound combinations describing the motion of snow in Robert Bridges' "London Snow":

While men were all asleep the snow came flying,
In large white flakes falling on the city brown,
Stealthily and perpetually settling and loosely lying,
Hushing the latest traffic of the drowsy town,
Deadening, muffling, stifling its murmurs failing;
Lazily and incessantly floating down and down
Silently sifting and veiling road, roof, and railing;
Hiding difference, making unevenness even
Into angles and crevices softly drifting and sailing.

Clearly this is no blinding blizzard, but a gentle but insistent, slow, fluttering, long lasting snow fall, almost surreptitiously invading the city.  Indeed, this passage illustrates several effects of verbal music discussed in this chapter.