Hey, Tim. I just ran across this post and honestly, it perplexed me given your experience and the past posts I have ran across here at the WBF. You mentioned that, "Instrument location only needs lateral and depth information". I quoted your entire post here, instead of honing in on just that one phrase. This way, things won't be taken out of context.
So, instead of a 2-D vertical plane of width and height (which I call musical wallpaper), you are saying that the musical wallpaper needs to be tilted 90 degrees toward you, and that's all that is needed? Like a horizontal line of sound with no height? If I am understanding you correctly here, that is still 2-D. It's just looking at it from a different perspective. A strange one to me, honestly, but that's besides the point.
In order for one to achieve a true 3-D sound stage, wrap around and room filling sound, are you arguing that height isn't a part of the reproductive effort? If so, if you would be so kind, please clarify. I know that a recording differs from the reproductive effort, but after mastering, all 3 aspects are introduced. Instead of 2-D wallpaper, regardless of which plane it's on, wouldn't one ultimately want the final product of 3-D sound?
IMO/IME, truly palpable spatial locationality cues only come from a system that offers all 3 dimensions. Lose one and you lose the aspect that so many people who aren't audiophiles almost never get to experience. Ya' gotta have all 3. Bonus points for perceived sounds being able to whisper2" away from your ear or well behind (read 40') your listening position. I often look out toward an object, nowhere near the speakers, and I can "see" the vocalist or instrument there. I can look up, well above the speakers and very easily and distinctly follow the sound as it travels. Listening to a studio recording, then switching to a live recording (even bootleg) of a large church....you can clearly tell the size of the venue from the ambient cues. Without the 3 dimensions, this would be unattainable, no?
Tom