So, what's the basic definition? I personally define Rock and Roll as music that is based in a heavily syncopated beat. What is that, you ask? Well, anytime you have a beat pattern, certain stresses fall on particular beats. Count off to yourself, 1-2-3-4, 1-2-3-4. Did you notice what beats your voice naturally stressed? Most likely, there was a big emphasis on 1, and then a slightly smaller stress on 3 (1-2-3-4). Beats one and three, in a 4 beat pattern, naturally get the stresses, because it's what our bodies want by instinct. Syncopation, is a deliberate frustration of this natural instinct. Although we want to hear the stress on 1 and 3, syncopated music puts the stress on 2 and 4. Try counting 1-2-3-4, 1-2-3-4. It's a little bit harder, right?
If you listen to any Rock song, you will hear this syncopation as it's rhythmic basis. It's what gives the song a drive that makes you tap your feet, and causes you to listen more closely. By frustrating what you naturally expect to hear, it captures your attention, and forces your senses to work harder to make sense of the strange beat. I theorize too that this is why Rock stereotypically atracts teenagers and those of rebellious mindsets. It's very beat goes against the norm, and rebels against what is natural, just as so many teens and outsiders hope to do.
So, there is a little peak into the history and make-up of Rock and Roll. To illustrate, I have a fun song for ya, courtesy of the Rock legends, the Red hot Chili Peppers. In this song, the percussion lays down a strong clear 4 beat, but hits the cymbal on every 2 and 4 beat for emphasis. You should hear it, and I guarantee that your toe should start tapping as well.