"slaves throughout the English-speaking South were absolutley prohibited from gathering to drum and dance in their own tradition"

To say that it was "absolutely" prohibited implies that it didn't happen - according to a book I once read called The Peculiar Institution, there was a great deal of sneaking off at night to surreptitious gatherings with slaves from other plantations, where drumming and dancing indeed took place. More generally, this book described an active underground, subversive African-American culture that developed in the South during the slavery era.

Having to do with New Orleans, though, I read somewhere not too long ago that there was a customary and tolerated gathering of slaves and free African-Americans at a certain square on Sunday afternoons, with music and dance for entertainment and amusement.

It should be remembered as well that there has long been a great deal of mobility of European and North American musicians, entertainers, and people generally, such that a musical innovation that comes about in New Orleans might not take very long to reach other centers - and backwaters. There was, apparently, a touring jazz band that played in Winnipeg, Manitoba, in the early 1900s. Two African-Canadian brothers moved from Toronto to - Memphis? - and opened up the Maple Leaf Club at which Scott Joplin would play, and after which he named his famous rag. During the slavery era, there were slaves such as Josiah Henson (not a musician, but he left a written account) whose adventures and misadventures would take them all over the eastern U.S., from Ohio to New Orleans, and beyond. So - influences all over the place, no doubt.

Okay - that's just some midnight rambling.