Even if you're improvising, the fact that beforehand you know certain things will work helps you make those improvisations successful. It really helps to have a certain amount of knowledge about musical structure.
“A trip to the mainland was a big event and happened maybe once a year, although now you can get across in a speed boat in seven minutes but then it was a long way away.”
“Eisenhower is my choice as the American of the 20th Century. Of all the men I've studied and written about, he is the brightest and the best.”