I distrust anything that you don't hear.
You write it down because finally, when it's written down you do get it out of your system somewhat.
In writing music, the structure of each piece is a very important factor.
But in the end, music is ultimately an aural art, pure and simple.
Of all the arts, music is really the most abstract.
A person improvising is sometimes very fortunate that just at that second things coincide.