The relative frequency and importance of composition and improvisation over a given player's life would probably make a study in its own right. In around forty-five years I have changed from regarding written composition as the ultimate objective of my piano music to almost a total embracing of improvisation as ends, means and everything in between. In my twenties and thirties I wrote dozens (possibly hundreds, I haven't counted) of piano pieces and recorded improvisation once every few months. At sixty-three, I have written out nothing for ten years and my present recorded improvisation frequency is about a CD every two weeks and accelerating.
What is gained and lost by writing things out ? By not writing things out ? I think we can dismiss the permanence of pen and paper in the electronic, digital age; that is no longer relevant to the central question. Could a composition perhaps be simply defined as a piece wherein I play pretty much the same notes, the same way each time ? I think so. Whether or not I actually make a visual approximation of the sounds on paper is irrelevant.
In the end I can only comment meaningfully on my own position. Both processes are so intrinsically personal, so woven into my own psyche, that anything I try to say stands a good chance of seeming strange, or even ridiculous, to another player.
My first and main practical problem with composition is rhythm - I cannot write out the spontaneous rhythms which deeply move me in easily transmissible form. I have tried and I don't think it can be done. From what little I have seen and heard of other creators and their activities I doubt they can either. In fact the better known they are the less capable they seem of grasping that a problem even exists; such is the power of two or three centuries of notational tyranny.
The second problem is that everything takes too long. To write out even a fumbling, halfway decent approximation of things I like playing takes on average about a thousand times as long as it takes, not just to play it, but to create it. Taken in conjunction with the average lifespan this fact is a pretty formidable case for improvisation.
Now those two reasons still do not exclude composition in the sense of a more or less permanent, repeated piece crystallising from my playing - whether written out or not. This does not happen like it used to with me. Why not ? I think the reason is the sheer volume of spontaneous ideas. Virtually every musical thought these days is a springboard to another. At every turn there is change, delight and surprise. I wouldn't have it any other way.
Do I not then possess this drive for final structure, a consolidated epitome of some deep-seated psychic state in the form of the polished gems which K implicitly describes as the ultimate creative end ? Yes, of course I do, but with me the "end" is the whole evolving organism itself - my mind, life and its colossal panoply of thousands of hours of piano sound spread over forty-five years (and hopefully a few more). Form exists but after the manner of a collection of organisms, species forever evolving, reproducing, cross-pollinating, according to the chaotic impulses of their environment, not of a static cathedral designed by even an architect of genius. To steal a brilliant allusion from Bronowski, talking about his grandchild in the Ascent of Man, an Easter Island statue is in the end not worth anything compared to a baby's face.
When I asked an old friend about these things many years ago he replied that people crave some embodiment of stasis to offset the truth of their own transience in a dynamic system - so they create things to "make a desperate mark on the wall - I WAS HERE !" I disagreed with him then and I disagree with him now - for myself - but I rather think he wasn't too far off the truth generally.
Topic: "My Favorite Melody" -- improv