Interesting takes on "holographic.
I would suggest a combination of both imaging and soundstaging for a true re-creation of holographic.
There would need to be width, depth and height of the soundstage itself, independent of the "image" factor.
There would need to be actuall depth layering, which is quite different than depth. Depth layering is more of a sense of instruments ranked behind each other - CLEARLY! - and not whole rows of instruments bunched up with each other so that you cannot determine if the flutist is behind or beside the trumpet.
Then, there is the imaging factor. The images must be very 3-dimensional: not just a bas-relief picture, but a sense of an invisible human being with a front and a back to their body. Or, in an orchestra, a sense of actually "seeing" the violins, bass drum, cellists, etc. In order for this to be complete, the instruments need to sound as though they have weight [e.g., the violinst sounds like he/she weighs 100 pounds, not 30 ounces] and are simply invisible, or, as has been written in TAS, "palpable." Touchable. And you can see the outlines of the way the instruments face: are they facing you, the listener, or are they facing each other, as perhaps in a string quartet. For this to be complete, one requires imaging specificity, which nobody talks about. Specificity means that the actual images' orientation is obvious, and I do mean, OBVIOUS! No guessing which way they're turned. Specificity combined with dimensionality and palpability create a solid "presence" in your room.
For the presence to be believable on a higher scale, it must then be placed into the recorded acoustic, replete with the air that obviously exists within the room. And the air must be light enough to "spread" when the instruments begin to bow, blow, strike, squeak or squeal. When the air moves around the instrument and the notes it creates in the air surrounding it, and these other factors are present you have a very high impression of holography.
The best imager I ever had was the WATTS -- back from 86-1992, when Dave was in the San Francisco Bay Area. The next best -- for me -- were the Avalons (Eclipse or Ascents; I only owned the Eclipse). In fact, after the WATT, nothing was quite as "right there! There! R-I-G-H-T THERE!" That was a combination of the WATTS (mine), the ARC SP-11(mine) and the Rowland Model 5 (mine) and 7s.
I also thought that the MIT speaker cable and interconnects of the time assisted: they had "bloom": the ability to allow the components' harmonics to spread into the air around the instrument -- in your listening room.
That's what Jonathan Valin is talking about when he says bloom: the air spreading outward.
I imagine many components these days image, but how many complete the illusion withe the blooming of the upper harmonics? If you want complete holography, this is a large starting part of the list. There are other factors, too.
