In English we have some common sounds that are used to fill spaces in songs like "ah" "la" "nah" "oh" "yea".
What do we use for Japanese songs?
So far I think I have only heard
As for the short shouts, Japanese popular songs are influenced by American culture, so you can hear almost anything that you would expect to be shouted in an American or other English songs.
As for the sound used for some length, I think
ら is the most popular one:
A standard song sang in elementary school:
You can hear it throughout this song:
This one is made solely of this kind of sounds, and includes some variaties (
I found one with
Conclusion is that
ら is the most popular (and sometimes even
や), and my very rough guess is that this has connection to the fact that the epenthetic consonant in Japanese is usually a liquid (r) or a glide (y, w) as you can observe in the phonoloical rule applied to vowel ending verbs:
mi-u → miru (見る), classically
mi-u → miyu (見ゆ),
mi-are-ta → mirareta (見られた)