You might wish to think again if you really believe you know even the least bit about jazz when you look at the preponderance of “style-within-a-style” genres. These sub-genres may have greater currency than you think. ‘Jazz’ these days is more a general term than a truly specific one. The style-within-a-style designations oddly have more usefulness (you know a little bit more accurately what it is you’re hearing) even if these constituent musics rarely reach audiences beyond their own communities.
Smooth-jazz
Most general jazz listeners won’t be aware of new developments in these areas until the sub-genres go overground to emerge blinkingly into the bright lights before often disappearing again to become the music of a narrow fanbase once more. Look at specialist websites and you’ll quickly understand why style-within-a-style artists stay close to home. Their music is largely unknown to general jazz fans and mainstream jazz media, in the same way that metal has a big following usually ignored by the mainstream rock media.
There are elements of older styles such as trad jazz that are also like a closed community. In trad’s case it’s for generational reasons rather than anything else, the music that an older generation knew in their younger days. This becomes music that through time is seen as a period music, and when it’s played by younger musicians it’s done as a homage to an era only not as a living and breathing resource unless it’s deconstructed. So “Rat Pack swing” and “Jazz Era” 1920s styles are the musical equivalents of costumes in a fancy dress shop. Where sub genres or a style-within-a-style have potency is when they come with their own language that no one really can speak because it’s so new. Prog-jazz is an example of this. Yet most of the prog-jazz artists are scarcely on the radar of more mainstream jazz fans apart from one or two of the pioneers of the genre, WorldService Project and Troyka.
Trad-jazz
The idea of “style-within-a-style” genres to its critics fosters a cult-like reverence that ultimately limits the audience unless that style-within-a style is so large that its narrow focus isn’t an issue. The language of smooth jazz will stick around and has already been rewritten through parody, homage even and more than surprisingly than you'd think paraphrase to flow into other styles that one day too will become styles-within-a-style. Jazz is too big and general a term to be useful any more, so boxing up jazz that bit more might actually serve a useful purpose for once.