Jazz listening: Is it about the music? Or is it about the sound?

Both.... It's about the sound of the music.

I will say this about albums.
Since I got my Bob's Devices Sky 30 SUT, I've gone back and listened to some albums that just sounded dull, but now many of them seem like they have come to life. What I mean by that is the sound is more lively, the definition and the sound stage have gotten better. It made albums I didn't really care for, listenable. 
I am most impressed.

It's both, no question, and one can have precedence over the other depending on my mood. I'm not a big jazz fan, but jazz  might be the best kind of music to test most hifi systems. Treble, bass and mid-range - jazz contains the entire audio spectrum in abundance. John Coltrane's Blue Train album is a prime example but there are many others.   

I hate spell check sometimes. That was supposed to be discriminate.
Anyway, better systems make everything sound better. You hear the antiquity better. The music and artistry are still there. In order to really understand some artists particularly horn and reed players, you have to hear them early in their careers when they still had lungs. People who shy away from very old recordings and 78s are missing a lot of very important music. Enrico Caruso and Louis Armstrong are great examples.
Both were genetic misfits who had lungs twice the size of ours. Both had no need of a PA system. 

There are people who listen to lame examples of music because it was recorded in a special manner. There are examples of great music recorded in a special manner. Find those.

Both!

I'm also a Bill Evans Trio fan. Big Time. Mitchel's "Song for Sharron" is on now and that's utterly moving to me. 

Isn't that the whole point of all of this; getting an evocative experience over and over or as Ben Sidran said "it's copacetic man" Heck yah. "Jesus Just Left Chicago" or "Blue Rondo a La Turk" (the live at Carnegie Hall version) both thrill.

Recordings of the likes of "Mingus Plays Piano", Teddy Wilson, Red Garland and Django Reinhardt are not amazing recordings but the music shines through.

Jarrett, Peacock and Dejonette on "Whisper Not" playing "Poinciana" is another one that sends me and the recording is good too.

Is sex about the sensations and release? Or about the communication, intimacy, closeness?
Is food about the interesting textures and flavors and how they're put together? Or is it about the emotional and physical satisfaction that results?
Are movies about the pacing, plot, and character development? Or about the immersion, excitement, and adrenaline burst?
To answer one or the other or both or neither is a good Rorschach test for members. It answers a question, "How should one live?" (Those who claim "both" are just as subjective as those who say one or the other, by the way. What they mean is, "For me, both!")

My MRI of the question reveals a philosophical question (as well as a personal and practical one). (And it's not "truly" a philosophical question -- that's just how I take it.)

Kierkegaard wrote a book about this basic question, entitled "Either/Or" in which he portrays two life views. From good ol' Wikipedia:

"The aesthetic is the personal, subjective realm of existence, where an individual lives and extracts pleasure from life only for their own sake. In this realm, one has the possibility of the highest as well as the lowest. The ethical, on the other hand, is the civic realm of existence, where one's value and identity are judged and at times superseded by the objective world.'