It's never occurred to me before to find out what it's plural or singular. I think the former.
lyrics
It is. "Did you hear those lyrics? THEY suck" "THESE lyrics ARE pretty good!"
Actually the singular for Lyrics is lyric, therefore you could use it too.. The thing is, that is more used the plural. Maybe if you're talking about several, and then you wan to pinpoint another you'll use the singualar? I don't really know. I use both! xD