...whatever its creators wanted it to be.
There are no "rules" in rock--that's what made it so dangerous AND pleasurable. It was what someone listening to it SAID it was.
Rock survived the corporate monster but died by suicide, when its creators grew up (or at least aged) and decided they wanted respectibility. The Rock n Roll Museum is its tombstone.
I remember when The Kinks were inducted into the R&R HOF, Ray Davies said, "Seeing everyone here made me realize Rock and Roll has become respectable. What a bummer." I agree.