> I suspect my definition of classic is the same as everyone elses--namely, a classic is something that was popular before I was born...

There may be another factor, too, namely whatever word comes after "classic." I'm pretty sympathetic to Howard's definition of "classic," dating back to pre-1949 or so, but "pre-1949 classic rock" doesn't really exist.

I'd call 1950s rock-n-roll "classic rock," but I wouldn't call jazz from the same era "classic" in any way. Operas and symphonies and so forth would have to predate anybody alive today by several generations to earn the "classic" label.

Might Black Sabbath be "classic heavy metal," even though it's clearly not "classic rock"?

You're right, though, as much as I'm muddying the waters with more objective criteria, there's no getting around the use of "classic" as relative to one's own childhood. Nevertheless, Ciaran is still wrong.