I read the wikipedia entry on pitch space, remarkable that people were intrigued by this so long ago. What is fascinating is this desire by so many people to find a way to visually represent and reveal all these relationships that occur in the acoustic realm. "We stand on the shoulders of giants".
By the way, let me congratulate you on your archive of graphics concerning these issues, it saves me an awful lot of messing around.
Observing your spiral graphs I see the limitations as you describe them, in the case of the second spiral where you add a G my requirements for spectrographic representation are different in that I only wish to show the acoustic content of a single instrument. However this is still relevant in the case of those instruments which can play more then one note at a time.
After translating it into 3D I can see the problems arising from the increasing scale. Some comments about this, you will find that the issue of acoustic/spatial relationships being skewed by depth perception are less problematic if you are moving around the object in a 3D space. I consider the second issue of semitones increasing in size being counter-intuitive a bigger concern. It did occur to me originally that this would be a problem, it seems to make more sense if it were the other way around. Interestingly enough, the fact that as you climb in pitch on the finger board on a string instrument your spacings get smaller, is an example of the inverse relationship we experience in the physical realm. So here you have a perfect example of the extent to which visual form can influence the interpretation through preconceived notions of geometric meaning of something which is essentially a consistent mathematical analogy.
One of my criteria for generating my imagery is that the fundamental aspect of an instrument's sound production is represented through the visual entity, hence in DFR each entity looked like a string. My interest in spiral spectrograms is they would be well suited to brass and woodwind instruments, as their shape is generic to the conical aspects of these instruments.
Ultimately I am interested in a variety of styles of spectrographic representation which can be mapped onto different instrumental entities.
I think the most important role of spectrographic content for my needs is figuring out which style of representation will best visually discriminate between the qualities of smooth tones and rough tones, for want of a better description. So those harmonic qualities that manufacture rough harsh sounds are presented in stark contrast to those that produce clean pure tones. Again this is also an information resolution issue. When placed in a much larger 3 dimensional music-structural context with multiple parts playing, there will be an inevitable loss of detail (except for close up shots), so to represent the fundamental principles that influence the tone quality of instruments are perhaps all that is necessary. Extra information which is designed to reveal other more obscure harmonic relationships may not be useful other than for academic purposes.
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