The Beatles are rightly considered one of the most progressive rock bands of all time. So it is easy to look back at their salad days and point out John Lennon, Paul McCartney, George Harrison and Ringo Starr as the early 1960s version of a boy band. After all, the group were well-marketed and hit the top of the charts with startling consistency. But, within a few years, they were already changing the game. After their album Rubber Sul, the group confirmed themselves as the rock icons they are now revered as. Not only did they begin expanding their counterculture...