The Birth of Rock & Roll

   This has some interesting reads.....https://case.edu/ech/articles/r/rock-n-roll                                                                                       

Your overview accords well with most of the histories of the era that I have read. 

Some books that I assigned in my Modern America History course that bear on the issue include (never all at once, although it would have been fun to make the course more than 20% about music): Hip: The History (2005) by John Leland; LeRoi Jones, The Blues People (1963); and William Howland Kenney, Recorded Music in American Life (1999). The last supports some of your pre-WWII generalizations, while the other two place youth culture front and center.

Add to these a full shelf of the leading works on American post-war culture and the spending habits of the Boomers when they were children.

I think you have a credible outline that highlights some of the ways that rock music developed.

I might also note that both The Who’s Tommy and Pink Floyd’s The Wall are stories of damaged children whose fathers fought in the war. This theme is not incidental to the music.

Alan Freed is credited with popularizing the term "Rock and Roll" as associated with the new music of the early 1950s. His view was "Rock ’n roll is really swing with a modern name. It began on the levees and plantations, took in folk songs, and features blues and rhythm". Rhythm and Blues is probably the greatest contributor to R&R. I dug up some old songs that may show some of the changes that brought about R&R. The rhythms of these three songs is essentially the same. The beat changes emphasis a little and the sound becomes what I would describe as more raw or rougher as time progressed.

1946 - Sister Rosetta Tharpe
1954 - Bill Haley and the Comets doing a remake of Big Joe Turner
Four years later in 1958 Chuck Berry was making history. The rhythm is still basically the same but the beats and chord structures have changed. Rock & Roll as we know it was emerging.

Here ya go:  https://youtu.be/ZveMYqEqJyI

Who doesn't like Southern rock (other than Neil Young)?

TV had a role in "selling" rock&roll to try and get the loyalty of the young viewers, it's true, but in the early days I think it was more the performance of the artists that sold the genre than either tv or radio.  Jerry Lee Lewis was known as "Killer" because of what he could do to a crowd (though it obtained a different meaning later on), Little Richard was another one that could work a crowd (even though he was "flamboyant", code for gay at the time).  The cross-over with the blues helped to sell it to white crowds, as there were artists on both sides of the Atlantic that were being influenced by the great bluesmen of the 50s.

He's not really around, anyhow...

https://youtu.be/ALR13MJLAs4

Actually I like Neil Young. He's still Neil but at 75 he's no longer Young.

for anyone who didn't get the allusion, Ronnie Van Zandt of Lynyrd Skynyrd wrote (in "Sweet Home Alabama"):

I like both Neil Young and Lynard Skynard...well, that's not quite accurate.  I like a bunch of Neil's stuff including his days with Crosby, Stills, and Nash, and I like Freebird .

Thanks. I'm not an academic, so I try to be circumspect and remain open-minded. My impression is one of a perfect storm where so many things had to happen within a certain time span to create what would become one of the most energized musical genres.  Do you think if McCarthyism hadn't been all but quelled by 1956 that it's tentacles would have also slithered into this nascent musical form before it could establish roots?