Methinks your time-line is misconstrued.
As the Celtic ppl's ran from the powers that be, they headed into the hills of Appalachia, where they found that smoking the blue grass will make you very thirsty for corn drippings.
Meanwhile...well, actually, way before this occured...the slave ships brought the blues to many of the forced immigrants, & they sang them a capella, since they couldn't afford instruments.
As time went by, the newly freed ppl began to alter their beloved blues, mostly because they were bored with them, & things really weren't as bad as they once had been, & jazzier sounds began to erupt from the southern villages as ppl now had enough money to buy instruments.
However, the landholders who once brought these immigrants to the country, FINALLY began to listen to their blues, &, since they could afford instruments, they began to play the blues (poorly, cuz they had little or no real rhythm). This new form of the blues encountered the Appalachian bluegrass sound, which then became country music, with a twist of lime.
The jazzists started to explore yet more musical territory, & found that certain rhythms & dance styles could get them laid, & rock & roll was born in the back seat of an old Dodge when Albert plooked Peggy Sue.
The rhythmless ppls still trying to invent country music got all caught up in trying to get laid, too, & Elvis started thrusting his hips, which drove the girls crazy, for some reason, & rock & roll soon became main-stream.
However, as these music styles continued to evolve simultaneously, they began to fracture into factions - rhythm & blues, the motor city sound, the philly cheese steak, and broken speakers begat distorted sounds for the masses.
Then the country fried rockabillistic poets found drugs, & the entire music scene changed once again. Psychodelica, funky smelly dance shoes, methed-up speed metal, & candy corn seemed to be all the rage with various groups of women (which is the only reason ppl played music at all in those dark years).
Eventually, all of this led to the invention of rap, which calls for geting laid even more than any other music form, as well as bitch-slapping, cap-popping, & serial killing. Also invented was the screamo (which seems to be a direct result of ppl trying to avoid the cap-popper rappist), emo (which bewails the results of said cap-popping), & electro (which has no relation to any form of music at all).
Somewhere in there, there was a fusing of classical with the more modern instruments, & the more modern lack of actual creativity or ability to play one's instrument, & new age was born & died quickly, except for the undead Yanni.
SMILE - it's the safest way to spread your cheeks!
