David Grisman on improvisation, 1993

I always think that really the only difference between improvisation and composition is a time factor.... There's a certain amount of what you "improvise" that's part of your shtick--it's the reason you can recognize Charlie Parker, because he is playing the same stuff every time, in a way....

But it's the creative process, and what I'm trying to say is that even though we can say it's improvisation, what we played today isn't totally different from what we played yesterday. I don't think anybody just improvises something that they've never heard before, unless they're somebody like [pianist] Cecil Taylor--I wouldn't really imagine that he knows what he's playing half the time, in other words that he could write it down.

From an interview with David Grisman and Jerry Garcia in the book Rock Troubadours