Assonance
The repetition of similar vowel sounds in nearby words.
Assonance threads a shared vowel through a line, as in the long “o” of “lone” and “road.” Writers use it to create internal music, slow or speed a line, and bind words together below the level of full rhyme. The effect is subtle, felt more than noticed.
Example
Poe’s repeated ringing vowel sounds imitate the chiming he describes, letting the poem’s music echo its subject.
The Bells · Edgar Allan Poe