Cradle of Filth, A gothic rock band from the UK, seem to use japanese to fit in with the song. An example is instead of saying goodbye, they say sayounara.
It is sung Saaa--you--naa--ra
As you can see, goodbye wouldn't fit as well- An attempt at making it fit:
Goo-ooo-ood-byee
I have heard it in other rock songs, but it is usually discrete...