The function of onomatopoeia in poetry is to create musicality in the spoken words, and reinforce the overall theme of the poem. Onomatopoeia is the literary term used to describe words that approximate their meaning with their sound. The word "pop," for example, may be used to describe the loud, jarring sound a cork makes when a bottle of champagne is opened. This literary device may be used in conjunction with other techniques to produce music through words alone. It can be used to force the reader to speak the poem in the exact manner the writer intended to illustrate the complete meaning of his piece.
Onomatopoeia in poetry is often used to create the rhythmical cadences of music, without the addition of actual instrumentation. Edgar Allen Poe's The Bells uses onomatopoeia in combination with repetition to call to the reader's mind the myriad of sounds made by sleigh bells jingling on a cold winter night. He first asks the reader to "hear the sledges" (line 1) decked with bells, and promises that their sounds promise a "world of merriment" (line 3). As the sleighs move over the frozen ground, the "silver bells" (line 2) tied to the sides make a "tinkle, tinkle, tinkle" (line 4).
The word "bell" itself, which is the focus of the poem and gives it its title, is also onomatopoetically used to suggest the full resonant sound a bell makes when it is first rung. The word itself is repeated ten times in the first stanza alone. The final six lines of the poem feature the word "bell" repeated 13 times to create the sense of a great symphony of different bells ringing as the speaker finishes his tribute to their music.
The use of onomatopoeia in poetry may also be paired with other literary devices to create theme. The musical sounding words when spoken aloud can repeat the primary concepts addressed by the actual words of the poem. Wilfred Owen mockingly pays tribute to those who die young unnecessarily in Anthem for Doomed Youth. He asks if "passing-bells" (line 1) will play for those who have needlessly died, and answers his own question by stating that only the "stuttering rifles' rapid rattle" (line 3) will play for such unfortunate ones. The word "rattle" calls to mind the sound a gun makes when it is being loaded with a bullet and prepared to fire.
The word choice of the onomatopoeia in poetry can be lyrical or harsh in nature. The word "bell" used by Poe is soft, drawing upon an open vowel sound to reproduce the swelling music that is central to the poem. In contrast, Owen chose a harsh "t" consonant to denote disapproval and disgust with the situation which claims the young. When combined with the consonance created by the guttural three repeating "r" sounds, the picture is created of many guns being loaded and fired, as the reader might see on a field of battle during a time of war. This grisly scene of death lends to the overall theme of the poem that war viciously and ruthlessly claims too easily the lives of young men.