Good points, Lox--admirably comprehensive, yet concise and to the point. Given the tensions between fans of the different schools of jazz, there is more potential for conflict here than in the tedious discussions about "what is folk music?"

Duke Ellington once said something to the effect that there is a lot less improvisation in jazz than is generally imagined--and the "jazz" of the jazz age was played from arrangements, and over time, though the improvisations of soloists seem to define jazz, what it sounds like really has more to do with the arrangers, like Don Redman and Gil Evans, than anything else.