Here's why:
* Consonants are usually repeated with the *same* vowel: The most common repetition is *alliteration*, which is the repetition of the *same* consonant sound at the beginning of words. For example: "Peter Piper picked a peck of pickled peppers."
* Vowel repetition has a term: Repeating the same vowel is known as *assonance*. For example: "The rain in Spain falls mainly on the plain."
Example of your request:
You might have in mind something like "sha-la-la" or "ba-da-da". This type of sound repetition is usually considered a musical element or a form of onomatopoeia rather than a specific grammatical feature.
If you can provide a specific example of what you're looking for, I might be able to give you a more specific answer.