Frederic Rzewski spoke at my college today, and said something I was pleased to hear (a lot of things, actually). Rzewski is one of the leading composers who’s also a fantastic pianist improviser, right? One of the greatest of our time. He said (I’m paraphrasing from memory), “When I was young, I believed in the statement that ‘Improvisation is composition in real time.’ But as I’ve gotten older, I’ve come to realize that improvisation and composition are not only different mental processes, but even opposed to each other. In composing, you’ve got to remember every detail you write in the piece. But improvisation is just the opposite: you have to constantly forget what you’ve just done so you’re free to do something else.”
I’m not an improviser myself and so couldn’t speak with as much authority, but, likewise, I’ve never bought the line that the only difference between improvisation and composition was speed. For me, composition involves loads of revision, and often a kind of backwards way of thinking, whereby you’re always changing was you wrote before in light of what follows it. Free improvisation is, by contrast, completely one-directional, because you can’t go back and change anything.
Rzewski also said, at the end of the talk, “We’re living in a totalitarian society, with the added disadvantage that we don’t realize it’s totalitarian, we still think it’s some kind of democracy. We’re controlled by forces that we don’t even know are out there.”