Producers of the era of the fifties were looking for a white artist who could take the sexy soul of Little Willie John and a horde of other black performers and cross it over.  Elvis did the trick.

In less than a decade, black music was all over the radio, the main delivery system at that time.  Some of it migrated to Europe, where it came back exploded as the British Invasion.  With Elvis in the army in Germany, and the Beatles in Hamburg, it exploded there as well.

However much he wishes to deny it, Bob Dylan added a level of social consciousness or conscience that had never hit the mainstream before.  He wasn't the first, building on Woody Guthrie and Pete Seeger amongst a host, but his explosion was a shot heard round the world.  When he went electric, it presaged the main event.

By the time psychedelia hit the world, the cycle was complete.  The joining of the drug and political cultures affected every art form, from the San Francisco Sound to French cinema.  Sexual barriers had fallen for good, accompanied by overt idealistic politics.

You could also argue that it wasn't long before the industry regained its footing, using glam and the heavier rock sounds to take the revolution back to ego-driven marketing concepts.

But it all really goes back to the melting pot that amurka was, and the influence of the former slaves' music was the primary driver.

The history of New Orleans music is the best example, mixing black-Afro and Carib sounds with the displaced French Acadians, with whorehouses providing the caldrons where the music was mixed.  Even 3rd generation white Texas fiddlers like Bob Wills went there to sop up the mix with their bread, taking Duke Ellington horn charts back to play on three-part (or more) electric strings.

When Peggy Lee turned Little Willy John's "Fever" into required cocktail party music throughout suburbia, the damage was already done.

Then the insane born agains brought abstinence back into the equation, completely forgetting the very sexy "Midnite Rambles" that were the most popular part of every religious tent show.  

Now it's the bedroom produced music of modern technology which will provide the next musical break.

"Life shrinks or expands in proportion to one's courage." - Anaïs Nin