Well, because everything's on paper and you don't get any more sounds or anything. I think it's best, especially in jazz, for a musician to learn to feel everything and teach himself. If he's going to play the classics - like one summer I went to a teacher for about 2 weeks and I knew what to do, you see, but there's a danger in losing the feeling in jazz because It's a self-taught music and since I was going to play nothing but jazz I benefited by not studying...