Thank you for one of the most insightful posts I've seen on Head-Fi in a long time.
There is much to think about and ponder. However, I'd like to raise one point for consideration.
We tend to think of the perceptual process as a one-way street. That is, there are a set of stimuli out in the world. They impact our sensory receptors, travel to the brain, and are eventually interpreted. If we can find the rules that our brains use for interpretation of those stimuli, we approach a language of subjective experience.
However, the particular process described above, the path from receptor to brain, is only one part of the perceptual process. We would call these "bottom-up" processes, as they start at the lowest level in the sensory chain (the receptor) and go to the highest (the brain). However, there is another class of sensory process that goes in the other direction. The brain can affect not only how we interpret messages from receptors, but can actually affect what we are able to perceive. Experience can actually alter the very messages sent from the sensory receptors. This class of process, whereby the brain affects the ability to perceive, can be called "top-down" processing.
A small implication of this is that there may need to be a Fifth Depth cue, relating to the expectation of depth. The perception of depth may depend as much, if not more, on top-down processing (the actions of the brain) than the actual physical stimulus.
Another problem then arises, since the brain does indeed affect perception at a level much farther down the line than just interpretation of the sensory signal, to what degree to our expectations of what something sounds like actually alter our perceptions and mold it to that image? In creating a language to describe the sensory experience, are we communicating a common experience, or actually limiting the experience to the dimensions of the language we have assigned to it?
