I just finished reading a very interesting book called "How the Beatles Destroyed Rock and Roll," which despite its title is not just focused on the Beatles; in fact only chapter is devoted post 1960s music. It's a general survey of popular music from 1900 through 1970.
The author's basic premises is as follows: From 1900 on musicians played a variety of styles and white musicians and african americans borrowed from each other, generally the white musicians borrowing more and getting the credit, such as in jazz. What they had in common, however, was that to eat you to play at dances and entertain people, who generally didn't go to a venue to sit down and watch music but to dance to music. Musicians had to know a variety of styles from jazz to foxtrots, etc. because that's what the public demanded. They wanted to dance to it. That is how musicians earned their living.
This generally held true, more or less, until the mid 50s because even though rock was developing (Bill Haley, etc.) it had to be danceable. However, the way people danced was changing, from dancing to one another arm in arm to the twist, etc. Music was still being developed jointly, with borrowing back and forth, african american musicians and white musicians influencing each other. It was a very symbiotic relationship. For example, Elvis was a toned down version of what was called "race" music where people like to listen to all kinds of music.
The advent of the Beatles and folk rock changed things. Where before you had to play for the people to earn your living, the white rockers who developed in the 60s, particularly from 1965-66 on decided they were going to play for themselves and not the audience, figuring they would still have an audience, plus they spurned the relationship that had developed with black musicians, who couldn't afford or have the luxury to play or write things they wanted to do. A good example of this is the Beatles decision in 1966 to stop playing before audiences and to just make records for themselves.
The end resul of this was that african american music and rock went their separate ways (e.g., development and growth of soul), probably to the detriment of white rock and roll. If you look at rock and roll in the late 60s on, you don't see a lot of african american musicians, the most notable exceptions being Hendrix and Sly and the Family Stone. This split led to the development of disco (i.e., it was danceable) and ultimately to rap, etc.
It's a small book (250 pages) and I recommend it.