I mean heavily accented singing. Like the one I posted below (used mandarin pronunciations for certain words and hybrid sounds for others)
Not only mandarin speaker in Cantonese, but also like Cantonese accent in mandarin or Japanese or English, or another accent in another language.
I guess it would only come into play if itís in a language you are fluent in. I think the guy in this file is pretty good, but I find heavy the accent a little distracting so I couldnít really get into the song.