From Keith Richards’ Life:
There’s something primordial in the way we react to pulses without even knowing it. We exist on a rhythm of seventy-two beats a minute. The train, apart from getting them from the Delta to Detroit, became very important to blues players because of the rhythm of the machine, the rhythm of the tracks, and then when you cross onto another track, the beat moves. It echoes something in the human body. So then when you have machinery involved, like trains, and drones, all of that is still built in as music inside us. The human body will feel rhythms even when there’s not one. Listen to “Mystery Train” by Elvis Presley. One of the great rock-and-roll tracks of all time, not a drum on it. It’s just a suggestion, because the body will provide the rhythm. Rhythm really only has to be suggested. Doesn’t have to be pronounced. This is where they got it wrong with “this rock” and “that rock”. It’s got nothing to do with rock. It’s to do with roll.