When I Googled rock and roll this definition came up:
a type of popular dance music originating in the 1950s, characterized by a heavy beat and simple melodies. Rock and roll was an amalgam of black rhythm and blues and white country music, usually based on a twelve-bar structure and an instrumentation of guitar, bass, and drums.
Every fan of rock and roll seems to have some built in definition in their minds about what music is or isn't rock. Some especially like to point out that certain music is not rock. Me, I think that trying to define it is somewhat against the spirit of rock music itself. Rock music should knock down barriers, not create new ones. It shouldn't be an exclusive club where only certain performers qualify as members. Me, I hate definitions that limit us from seeing music as music within a broad spectrum broken down only by vaguely defined terms. If anything, rock music is the mongrel of popular music. It is not a pure breed, with easy to follow bloodlines. Some rock music is loud and raucous, but it can also be melodic and sweet.
For me, if there is a guiding spirit of rock music, it is that of freedom and fun. It is pop music. It can be heavy or light, serious or frivolous. It is as disposable as it is important.
Nobody can pin down rock music. It defies definition.