I saw some fascinating viewpoints in this area and have a somewhat unique one myself that I would love to share. This is, of course, a very personal viewpoint. I hope it touches on some issues thatothers grapple with as well ;-). Somewhere deep inside of me I tend to view my music as something to be performed for an "audience", but my definition of audience sometimes changes. Most of the time, while I am even practicing scales, I imagine that someone is listening to what I do. This helps push me to "perform better". It sort of keeps the stakes a little higher.However, there are times - particularly when I pick classical pieces to practice - that I simply play for myself. Every once in a while this will include something from my "foreign language studies" like a tune sung in French or Arabic that I just wouldn't normally perform or play. If I personally want to hear something the audience can be myslef alone, but I also consider a difference between a more anonymous group and one I know relatively well.
I suppose one of the big differences between my general practice where I am considering performing in front of people and these special moments is the committment to composition. I can be entertained fairly well by beautiful music and certain compositions - like Bach or a pretty melody - just "please me" to play whether someone is lsitening or not. On the other hand, much of my practice is geared towards jazz that his less devoted to the composition itself. So, during my practice I am often doing my "own thing" and not paying attention to someone else. It is best said that when I stop concentrating on what I am "doing" and concentrate on what someone else has "done" I find it personally very satisfying and entertaining to play these things for myself. This is when I can be an audience at the same time as being the performer. I would still say that 80% - 90% of my practice is really devoted to preparation for performance.
Performance, for me, has hit a rather insteresting stage. Most of my life, as a member of an orchestra, jazz band, marching band, choir, Bar mitzvah band or something of the sort, I have been performing regularly in groups of various sizes. Rarely has this focused much on myself, but you do get used to being in front of "people" as a result. I also took some time out to play in a group in which I was the "lead" for a while with some of my jazz. The truth is that the most exciting "audience" to me is people that I know that share an interest in what I do. You might say that an "anonymous" audience simply has less of a link to the performer, but I really enjoy playing in front of members of the band itself. The reason is (I think) that I perceive the "normal audience" to be more devoted to being entertained than to what I am actually doing. Other harmonica players and other jazz musicians tend to carry an inherent curiosity about each other does and are far more capable of picking up the subtelties of what is going on. They are less demanding about being "entertained" with my very best licks and more into how I handle the fuid situation we call the "moment" ;-).
Constantly playng my jazz to entertain is something I find a little taxing at times. As a fanatic about jazz I am freely ready to admit that there is an element of the music that is geared towards the musician and not necessarily the audience ;-). Jazz "can be" self serving. There certainly are very informed jazz fans out there (many who know and have experienced much more than myself), but the musician is given tremendous leeway just to "get his rocks off". Thus, there is an element that is shared amongst the artists that goes beyond entertainment. This is aprt of what is a performance art and can be very fascinating - but also extremely subtle. I do believe that there is and "art to entertaining" and that this is a part of, but somewhat distinct from the art of music itself. Entertainment is geared towards the audience as well as the medium and subtlety is a technique that can exclude a part of the audience in this context. Some situations don't lend themselves to subtle performance art and are more amenable to good entertainment - to which there is an art ;-).
When I go to "entertain" I often find myself gravitating towards "simpler stuff". I like having vocals, playing tunes people actually can recognize (right Ron!) and things that stir the memory of members of the audience. With jazz, some folks will like it and others not. With pure entertainment in mind it is more choosing things that can spur a large "cross section" of the audience and help create a really strong bond with them. A good singer, a few blueses and an old standard or two usually make for a nce "Things Ain't What They Used to Be" type of performance in comparison to the totally instrumental and specific style of jazz I usually play. this allows larger cross sections of the audience to connect in some way with what is going on.
So, if a tree falls in the forest and nobody is anywhere near it, I am reasonably sure that something occurs that would meet a scientfic definition of "sound", but I am not always sure it makes "noise" ;-). Much depends on your personal outlook. There are times when playing is merely for my own personal pleasure; however, for the most part, I need to share it with someone to make the cycle "complete". For me personally, I tend to get more artistic pleasure out of playing things that broaden my perspective by myslef than things I do regularly. I also get a real sense of accomplishment and gratification when I am able to entertain as well as just perform. It is from this perspective that I have begun to use the phrase "the art of entertainment". Some things are for me personally, others are for me to share with my "peers" and, finally, there is some for me to share with "anyone" as well. I don't think art can happen in a vacum or without any sesnsory input at all, but I do believe that some art is very "personal" and less important to share. Once you know what or who your audience is it is much easier to go out there and "make art" - even if the audience is just yourself ;-).
In the end, my favorite way of sharing my jazz with others is at jam sessions. Here is where I can do what I "like to do" in a setting with others who have devoted much time to the same sort of thing. SPAH was an exceptional experience in this sense. Everyone around was interested in what I was doing and had something to share "in return", making the dialogue aspect of it very exciting. What resulted may not have been a carefully framed picture that stood the test of time, but there is an element of jazz that is created and then "immediately destroyed" in the sense that once the moment passes the actual art is forever "lost". Not everything is meant for posterity. This is why art can take place for a single individual at a single moment playing in their stairwell for sound ;-). Anyway, hope you enjoyed my take on the issue.