The existence of feedback is absolutely essential to art. For instance, it is in accusations that contemporary composers pay no attention to their audience that the most serious potshots are delivered. Leaving aside the viability of that criticism, it is communication at some level which facilitates relevance of any kind, and it is a chain of mutual communication which is necessary for transcendence. In other words, without some sort of feedback process, a one-step communication attempt can go only so far. This idea is an obvious one, but one which is applicable to many areas of musical endeavor. Some people seem more than happy to break the chain, or as my grandfather used to say, "There's what he's thinking, there's what you're thinking he's thinking, there's what he's thinking you're thinking he's thinking, etc." I run into too many computer-oriented people who will say "I knew what you meant, but I know you didn't know I would" when they are quite wrong on the latter. It is a failing of a certain kind of personality, and absolutely anathema to high art. To have real communication, let alone to have a mutual transcendence, these levels of thought must align, or at least not be deliberately broken by one side. Perhaps more illustratively, if these levels can align, one no longer has a one-step or two-step communication chain, but one which might become continuous rather than discrete. The shift from discrete to continuous thought is one marker of transcendence, and a process which mathematical feedback relationships can illustrate.
At its most tangible level, artistic feedback involves simply giving an artist one's impressions, whether critically or just off-the-cuff. Of course, the need for feedback is one area which informed criticism is intended to fill, i.e. it is intended to be beneficial to art. Criticism at its best can also help other audience members better appreciate something, since as the various factors are better understood they can both be more thoroughly enjoyed as well as included more strongly in the feedback loop. There is a fear in some circles that reading criticism will diminish one's enjoyment, but the fear is only justified in the following way: If the criticism is poorly articulated, or simply not easily understood, one can become disoriented by it, such that one's mind is attempting to understand the criticism rather than appraise the art. This danger is always present, and the same can be true of an artist's apprehension of criticism. In some cases, of course, the feedback is simply worthless. If one understands that it is worthless, it can be casually discarded, but not if one has lingering doubts. In that sense, particularly for an artist, there are times to withdraw from feedback, especially if one becomes confused by it or simply wants some silence in which to order one's thoughts. Withdrawing permanently from feedback can never work, although some people prefer responses in more indirect forms, and to their credit that approach can sometimes yield more honest reactions.
Beyond ideas of transcendence in the highest art, feedback can be necessary just to get to the first order of understanding, and indeed it can shift the locus of the entire process, especially when embarking upon something truly new. There are issues of credibility in that case, and various cases of "can't get there from here." In other words, one can make an initial attempt at composition or interpretation which would ultimately be accepted if it had culminated some more obvious path, but which is rejected as too bold. Maybe later someone will think you are ahead of your time, but really, one wants to be in one's time in order to avoid some rather substantial frustration. How silly is it to make partial attempts at articulating an idea which one already has fully formed in reserve? In some ways, very silly, but in terms of allowing the feedback process to catch up (or precess as I have termed it), it might be necessary or be performed eventually by someone else who has no cognizance of the result. Feigning ignorance is, after all, a particularly delicate task. One thing I learn again & again is that one can lead one's audience, but not from too far in front. This fact is highly significant for understanding the "classical coincidence" (as I have termed it in one of my more indignant rants), as the aims of composers and a new class of listeners aligned in a particularly strong feedback relationship for an extended period of time in order to produce what we have come to call "common practice" music. The older music was basically too intellectual for the new audience.
Especially in the electronic age, feedback in music takes on another layer of meaning. Amplification and explicit feedback relationships have continued to appear sporadically in avant garde music, and of course electronic amplification is integral to the way most people hear most music. Bizarrely, Carnatic concerts are usually amplified heavily, and the plethora of speakers makes the idea of feedback quite (sometimes painfully) explicit. Yet, a top artist will "play" the whole ridiculous conglomeration to good effect, including looking at the audience (on whom it is usually asked that lights continue to shine). Because precise interval relationships are so important to Indian classical music, this sort of aid to interfacing with varying (and frequently substandard) architectural settings begins to make some sense. The issue of architecture and acoustic feedback has also become increasingly significant to medieval music today, both for its concrete applicability to touring artists (also frequently in poor facilities) and on account of suggestions regarding how acoustic feedback may have affected early musicians & their choice of tuning. This is a particularly exciting, although speculative area, including the way cathedral reverberations affect rhythm & tempi. Indeed, physical examples of feedback of this sort help one to ponder the relationship between sound and larger cosmology, and so we are back to general alignment and transcendence. The notion of making acoustic feedback more explicit in postmodern music, via amplification and/or spatial effects, is at least partly a reaction to this relationship. The key to making it work is, of course, bringing the chain of feedback into the human domain through listener apprehension.