Assonance, a writer’s best friend.
Assonance is one of my favorite literary devices. It is the repetition of a vowel sound. Like bike and white. They bear some resemblance to a standard rhyme, yet is much more freeing. Well used it can help sustain rhythm and add to the musicality. Take the opening lines from Dylan Thomas’ Fern Hill: Now as I was young and easy under the apple boughs / About the lilting house and happy as the grass was green, The assonance is in some cases strong, on the forefront of the poem’s sounds, and others it’s more muted. The “ow” sound of boughs/about/house is very present, but the subtle /a/ of and/happy/as/grass and perhaps even apple are also there. And depending on how deeply you want to look into the line, the “uh” of young/under/was.
Is that looking too deeply at the lines? Perhaps. I always wonder that, but as an experiment I’ll grab the opening lines of a Billy Collins poem, “Fishing on the Susquehanna in July”: I have never been fishing on the Susquehanna/or on any river for that matter . There’s the been/fishing/river, subdued assonance, but for the most part the sound is loose. Not to say the poem isn’t good, because I’d be the first to argue on the contrary, but the musicality isn’t as dense as that of a lyric poet like Dylan Thomas. Not every poem has to be dense, but it is always nice to catch your reader’s ear once in awhile. Slight rewordings during the editing process is a wonderful little bit of tweaking that greatly benefits the poem.