Rock n roll is a definable thing. It may be a broad catagory (Elton John vs Metal, for example), but it is NOT all inclusive.
Maybe a distinction between rock n roll and plain rock is in order?
Rock n roll was what it was originally called. It was mainly white boys playing ripped-off boogie-woogie blues and singing about holding women's hands inappropriately and other stuff that was frowned upon back then. The early pioneers explored the other two crucial elements of the rock n roll trinity, namely sex and drugs and the heroes were the ones that took all three TO THE WALL. Some of them died, some completely defied medical science and actually survived.
This became the benchmark - sing songs that upset parents while showing the kids how to party like you mean it. Of course, every generation it becomes harder to upset the parents, since they were brought up listening to the shit that upset the hell out the previous generation of parents. You have to push it further. Louder, noisier, more sex, more drugs. Our great great grandchildren will attend concerts where the lead singer swallows 8 kilos of crack and then fucks a bunch of farm animals while screaming incoherently until his liver explodes.
Sure you could probably buy a ticket for this gig right now but you'd have to go to Tijuana or Eastern Europe. In another couple of decades it'll be mainstream. Grade schoolers will be practicing "Fuck this sheep til my liver explodes" to sing to the parents at the school concert. The next generation will probably have to start killing people just to raise the bar.
The "roll" part was dropped in the 80's when Metal came along. Roll is too soft for a moshpit. No one rolls in there. You Rock, that's what you do.
