I think that by including the terms "heretofore unknown" you're getting yourself in to trouble. Any visual medium must have a referent in the known world to convey any sense of meaning. With post-modern abstract artwork, that referent is other artwork. With music, although it does not have a visual referent, it has an auditory referent to sound. While it would be possible, I suppose, to compose a piece of music that had no auditory referent to any known or recognizable sound, it would be utterly unintelligible. It sounds to me like you're just suffering from that age-old photographer's angst - "is what I do 'ART'?". Photos of rocks and trees and even other manmade objects remain at the level of representational records when no effort is exerted to structure that representation in such a way as to ADD meaning to the image. It may be simply a matter of composing the image to emphasize pattern, form, or texture, or it may be viewing the subject from a distinctly unexpected viewpoint. It may be photographing the subject in such a way as to most closely mimic the actual way the human eye sees the subject, and as such, raises questions about the human experience of interacting with the subject.
In short, to me the distinction between art and photomechanical representation is purely one of intent - if you have the intent to do more than create a photomechanical representation, it is art. This says nothing at all about how SUCCESSFUL the artistic endeavor is.