First of all, what do we mean by rhythm in poetry? It's more than just the beat, which is where we find rhythm in music. It's the flow of sounds, the patterns of emphasis, in the poem. But perhaps it's easier to understand rhythm by the mechanisms which contribute to rhythm. One is the repetition of words. Another is the patterns of sounds, of stressed (emphasized) and non-stressed syllables, in a poem. This second kind of pattern is the one most people refer to when they talk about a poem's rhythm. This rhythm comes from the interaction of the poem's meter and the way we we would normally pronounce the words/sentences. There are three major systems of meter in poetry:
strong-stress or accentual system (focuses only on stressed or accented syllables)
accentual/syllabic or syllable-stress system (takes into account both the number of syllables and which syllables are stressed or accented)
syllabic or quantitative system (counts only the number of syllables with no regard for stress)
The strong-stress system was the first used in English poetry. It was used in Old English or Anglo-Saxon poetry. The Anglo Saxon line was typically divided into two halves; the space between the two halves is known as the caesura (actually, any pause that falls near the middle of a line is known as a caesura; it isn't confined to Anglo-Saxon poetry!) In the following Anglo-Saxon poem, note how each line has four stressed or accented syllables (in bold), two on each side of the caesura.
I have la bored sore and suf fered death ,
and now I rest and draw my breath ;
but I shall come and call right soon
hea ven and earth and hell to doom ;
and then shall know both de vil and man ,
what I was and what I am .
You can read "Western Wind," another Old English poem, the same way:
Wes tern Wind , when will thou blow ,
The small rain down can rain ?
Christ ! If my love were in my arms
And I in my bed a gain !
You may note that the meter looks like iambic (an unstressed syllable followed by a stressed syllable) at many points in this poem; this is no doubt because iambic is the meter that we use most naturally in our speech. Note, though, that this meter doesn't seem to worry about how many syllables are in each line or half line, or whether the stressed and non-stressed syllables follow a regular pattern. What is regular, though, is that there are two strongly stressed syllables in each half-line.
However, we don't see much poetry metered this way except Old English poetry and poetry by poets who imitate the Old English style. Most poetry we read (until the twentieth century, anyway) tends to use the accentual/syllabic or syllable-stress system. This system counts the number of syllables and the pattern of stress or accent. The basic unit used to measure meter in this system is the foot. A foot can consists of two or three syllables. The most commonly used foot is the iamb, which consists of one unstressed and then one stressed syllable. It's denoted by the symbols U / . As we've noted, this is the stress pattern which we most often use in normal speech: I'd like to know ex act ly what she said .
The iamb is said to be a rising rhythm, because energy builds up toward the second half of the foot. The second most common foot is the trochee , which is the opposite of the iamb, a stressed or accented syllable followed by an unaccented one: / U . The trochee is a falling rhythm, because energy is concentrated at the beginning of the foot and falls away toward the end. Poe's poem "The Raven" makes use of a basically trochaic meter:
Once up on a mid night drear y, while I pon dered weak and wear y,
O ver ma ny a quaint and cu rious vo lume of for got ten lore --
You could argue that the falling meter parallels the speaker's weak and weary state.
However, so far we've only accounted for the stresses or accents, not the number of syllables. The number of syllables are also counted in feet; for example, a 10-syllable line composed of iambic feet would be called iambic pentameter (pentameter for five feet). Lines with only one foot are in monometer ; two feet, in dimeter ; three feet, in trimeter ; four feet, in tetrameter ; six feet, in hexameter ; and seven feet, in heptameter. The Poe lines above are in octameter (eight feet). Keep in mind, though, that not all feet have two syllables! If you look at the table on p. 733 of your textbook, the anapest U U / and the dactyl / U U are basic feet made up of three syllables. So if a line were in anapestic meter, and had twelve syllables, it would be in tetrameter (four feet), not hexameter (six feet).
As you may have already figured out, most poetry does not follow its meter strictly. If it did, it would sound monotonous and sing-song. Alexander Pope, in his eighteenth-century "Essay on Criticism," (really a long poem), makes fun of poems which stick too closely to an iambic pentameter:
And ten low words oft creep in one dull line :
While they ring round the same in var y'd chimes ,
Note how he duplicates the sing-song of the strictly followed iambic pentameter in his lines.
So how does poetry avoid a monotone? It does so by the way the meter interacts with the rhythms of natural speech. This interaction can also be referred to as "variation," or "tension." My favorite description for it is was given by one of my professors, who called it "the space between speech and meter where poetry exists."
Let's look at the first two lines from Wyatt's "They Flee from Me."
They flee from me that some time did me seek
With na ked foot stalk ing in my cham ber.
Although the first line falls easily into iambic pentameter, the second does not. It sounds quite awkward to say "stal king" or "cham ber," as a strict adherence to iambic pentameter would require. Stressing my seems to be optional - it just depends how you would say it. This tension between the initially established meter and the rhythms of normal speech are what give the poem a unique, interesting rhythm.
Many contemporary poets use no preordained meters, but instead let the poem fall into a less regular, arguably more natural rhythm. This practice is known as free verse. ( Blank verse is poetry which follows a regular meter but does not rhyme.)
Walt Whitman's poetry is a good example of free verse.
Of course, the big question is why pay attention to meter at all? The answer is that it's important to be able to tell if the meter contributes to the overall meaning of the poem. As described in the Bedford Compact Introduction to Liteature, a good example of meter corresponding with meaning can be found in Timothy Steele's "Waiting for the Storm." In this eight-line poem, the speaker is waiting beneath an upturned boat as a storm begins. The poem is primarily in iambic trimeter, but there are some significant variations. Perhaps the most important one occurs in the last two lines:
Then the first rain drops sound ed
On the hull a bove my head.
We get four stressed syllables in a row with "first rain drops sounded," paralleling the heavy beating of the raindrops on the hull above the speaker's head.
Still other factors contribute to rhythm. One is the interaction between sentences and the ends of lines. If the poem's line endings tend to correspond with the ends of or breaks in sentences (signalled by some sort of punctuation), they are known as end-stopped. This type of line makes it easy for the reader to pause at the end of the line. If the sentence does not stop or break at the end of the line, but instead moves the reader quickly to the next line, it is called a run-on. In the following excerpt from Auden's "Musee des Beaux Arts," the first and fourth lines are end-stopped, but the second and third are run-on.
About suffering they were never wrong,
The Old Masters: how well they understood
Its human position; how it takes place
While someone else is eating or opening a window or just walking dully along;
Perhaps the two run-ons combine with the comparative length of the fourth line to give a sense of how most of us just move quickly along in our everyday lives, while terrible suffering breaks short the lives of others (as the comma at the end of the first line abruptly separates "About suffering they were never wrong" from the phrase to which the "they" refers, "The Old Masters").