it could be argued that improvisation is nothing more than the spontaneous regurgitation of what one has already learned.
but as sam harris says - he doesn't even know what he is going to say next or what the next thought will be.
as such, that could be what improvisation is.
not knowing what will come next
not containing what will come next.
it isn't so much the pattern that one plays.
but it is the spacetime of that pattern.
same with words.
we don't "invent" words on the spot. that is nonsense.
it is the usage and quantization of those words.
a book is controlled text on paper.
a good conversation is a spontaneous challenge of words that one cannot preplan.