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Bakazuki
Since: Jun, 2009
2014-01-31 23:28:23
Have you tried looking in the Music Tropes index yourself, particularly the Singing tropes and the Lyrics tropes folders?
I can't seem to find an exact match for what you're looking for (i.e. songs with lyrics switching to various languages), but perhaps you'll have better luck finding something related.
Chabal2
Since: Jan, 2010
Bakazuki
Since: Jun, 2009

Is there a trope for multilingual songs?