rhyme, vowel
韵 centers on the musical quality of language: the matching of sounds in rhyme and the resonant flow of vowels.
韵 is a variant form of 韻, combining 音 (sound) with 匀, which likely contributes a phonetic element. The exact historical development of the 匀 component is uncertain.
Sound 音 on the left and a balanced, even shape 匀 on the right suggest sounds that match evenly—like rhyming words or flowing vowels.
For イン, imagine the sound of a rhyme echoing in an inn: inn -> イン, and the vowel sounds resonate through the room.