Music is naturally abstract, for the most part. Vision is inherently concrete. Music constructs an internalized world, whereas vision expressed the world around us. These characteristics further complicate the task of translating music to image. But during the course of this investigation, I was struck by two things that may help to bridge these differences.
First, I was astonished to see that the grouping principles that are used for parsing visual and auditory input were so similar. This implies a stronger link between visual perception and auditory perception than I had expected. It seems very likely that similar neural structures are at work, at least in this very important process of segmenting and grouping. And if similar structures are at work at this level, then it seems likely that there is some further similarity in earlier parts of the perception process, at least at the point of preparing sensory input to be presented for grouping. A further implication of the presence of the perceptual act of closure in both vision and sound, is that both senses can invent and inject material into the experiential stream. Both senses present an experience that is substantially based on guesswork, assumptions and fabrication. That the path from sense organ to sensory experience is this convoluted and constructive seems to allow for greater possibilities of alternative paths to generating this experience.
The other thing that I was struck by is the inherent plasticity of the brain. The brain has remarkable abilities to modify its own function if presented with the right kind of input. Some research has suggested that the some of the visual cortex in blind people and some of the auditory cortex in deaf people comes to participate in the other active sense. It is widely known that our visual system can adjust to seeing upside down through image-inverting glasses over the course of two weeks. It is therefore not unreasonable to suggest that the brain might meet well-designed attempts to express music visually halfway. This would require significant exposure to the appropriate stimulation. This is only going to happen if the visual translation of music has an inherent and sustaining aesthetic value.
Certainly musical information can be encoded, and the code can be learned. But I believe that if it actually is possible to convey the experience of music to someone who is deaf, it will not be achieved through cognitive association alone. While music may not be specifically bound to hearing, it does appear that hearing induces neural structures that are receptive and responsive to music. It seems to me (unschooled in this field though I am) that the experience of hearing and the experience of vision, reside neither in the sense organs, nor in cognition, but in the intermediate space of the neural structures of the perceptual cortices. An integrated experience of music would require the development of appropriate neural structures. We do not spend a lot of time engaging with dynamic abstract visual stimulation, and so music-related structures might not be naturally encouraged in the pathways of visual perception, as visual perception reaches towards the recognition of concrete forms in the world. However, one senses in the fervour of those who have chased after this notion of Visual Music over the centuries, that some people naturally develop a sense of visual musicality and that this unique experiential world expands under extensive exposure.