ASSONANCE.
Consists in the repetition of vowel sounds without repetition of consonants.
The relatively close juxtaposition of the same or similar vowel sounds, but with different end consonants in a line or passage, as in the phrase:
"And looked down one as far as I could".
Looked rhymes with Could in the same line of the verse, although they dont have the same consonants.
Assonance can give musicality to the poem.