Your reference for "the absolute" sound?

Yeah, the absolute sound is live music, or any non-reproduced/non-regurgitated sound for that matter.  The crowd at the baseball game.  Kids playing.  The neighbor screaming outside.  Sidewalk buskers.  A lawnmower.  You can choose between hand-powered or gasoline-powered.   A Harley blatting by.  One of the best sounds I ever heard was a 1960's V-12 Ferrari careening its way down Sunset Blvd. in L.A.
When it comes to music, the best live sound I ever heard was courtesy of Herbert von Karajan and the Berlin Philharmonic at the Dorothy Chandler Pavilion in L.A.  I worked at Tower Classical Records at the time and the Polygram Rep laid a Founder's Circle ticket on me.  Then there are the jam sessions I've sat in with at various low rent bars & pizza joints.  Though my wife denies it, I like to call myself a fiddler.

edcyn, glad you mentioned the V-12 Ferrari sound.  I was lucky enough to have raced at Road America in Elhart Lake, Wi. and that sound is music to my sports car loving ears.  This has nothing to do with audio, but once at a Formula Ford and other events race at Road America there was a man that had a semi tractor trailer with a half dozen classic Ferrari's in it with his own crew to care for them.  And it seemed that the young lady on his arm was not likely his daughter. 

The absolute sound? Hmm. Hard one. But on the top of my personal list would be Sonny Rollins at the Bottom Line in Greenwich Village. He extended "Don't Stop the Carnival" for what seemed 15 minutes. I've been blessed to hear lots of great musicians, but that remains a highlight. oh yes, 15 feet from the great man's horn.

On the complete other end, when music quality was not the point, mosh diving at CBGB's with the DK's on the stage...

Elastic. Temporal...Points in time. Memory and Age dependent, etc. There isn’t one, even at the individual level.