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

Devil music.  Switch to rock.

@jdmccall52 Thoughts and prayers are with you!

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.