I am sure many composers simply improvise and used the good bits as part of a composition for inspiration, there's many parts you could take from this recording.
That is exactly how I used to form the large number of pieces I wrote out in earlier years. For piano music at least, I am sure you are right, and that many of the best piano pieces had their origins in improvisation. The fact that famous composers of piano music, old and modern, almost without exception, were fluent and habitual improvisers reinforces this hypothesis.
Some parts of this sound really good like a very passionate romantic piece. I have many improvisations which to me have glimmers of nice and then bits which are like smudge marks
I like those smudge marks and have grown accustom to hear them but on first listening they are always a little interrupting. I use to record improvs through midi and it was real fun going back and cutting out the bits which were no good.
My problem, one of them anyway, is that what I think is good or bad is impossibly unstable. One day I listen to a recording and think, "Those bits are very poor, perhaps I shall delete the whole file." Then the next day the same bits make me think, "That's good, how on earth did I play that ? Was I really going to erase it ? I must have been mad." I couldn't possibly trust a first listening, and certainly not within a day after recording. There are peculiar distortions which take place with me. It seems like five minutes, but I have been playing an hour and am utterly exhausted.
Another, possibly deeper obstacle to crystallising compositions out of them is that I cannot notate most of the rhythms I play which move me most deeply. Indeed, over the years I have concluded that only a small fraction of perceptible, spontaneous rhythm of any complexity can be written unambiguously at all. Whether this is a general truth, or just a reflection of my own lack of training, of course is not for me to say. Thirty years ago, I studied composition with a very prominent local composer. He told me my rhythms were simply out of time, my harmonies were wrong, and that I must start to create my music in terms of notation. I made a sincere effort for some months but couldn't do it. Despite all effort, I still preferred those wrong rhythms and harmonies to his right ones.
A third reason is time. It takes me an hour or more to write out even a poor resemblance of a few seconds of most of the stuff I play. I really hate the act of writing music, it makes me very grumpy. I used to carry a completed piece, even a simple one, around in my head for months sometimes because I couldn't bring myself to the task.
I am not helpless at some types of notated composition, as you know, particularly ragtime, stride, swing and some romantic forms. I have a large heap of it from earlier decades. However, for the reasons mentioned, and one or two more, I feel my sort of brain was somehow built for improvising. My teacher in my youth told me as much, but of course you never take any notice of anyone when you are young.
Anyway, thanks for listening, I always pay attention to what you say.