I missed Art's question in post #3 above, but checked back after reading Martin's reply. I have something to add ~ it might be more speculation than verifiable historical fact, but here goes anyway:

New Orleans, as an international port, has always been a fairly cosmopolitan city, and has had a sizable Jewish community as long as any American city has. During the years when jazz developed, there were Klezmer bands active in the city, and there certainly must have been Jewish musicians with Klezmer backgrounds playing in the popular dance orchestras that were part of the breeding ground for jazz. Indeed, it is very likely that (as always) some musicians played in more than one band at a time, and perhaps even more likely that one or more hotshot clarinet players held positions in Klezmer and general-interest outfits simultaneiously.

There certainly is a similarity between the clarinet parts of Klezmer recordings and early jazz recordings like those of Sidney Bechet, just as Art noted above. This approach probably predates Sidney, going back to the times before recording technology.

I've also heard and read that there are parallels between the makeup (instrumentaiton) of the typical Klezmer group of the 1880s/1890s and the classic trad-jazz lineup. I can't elaborate or argue this point, just pass it along. The prominent role of the clarient in both genres is pretty obvious, of course. The violin/fiddle seems to be much more important in Klezmer than in jazz, but some writers ahve pointed out that violinists were important figures in the early days of jazz.

So, maybe jazz and klez did NOT develop "separately but equally." There is some evidence that Klezmer musicians were involved, to some extent, in the development of jazz in New Orleans (where, as we all know, jazz first emerged).