When he was asked for a definition of jazz, Louis Armstrong liked to answer: "Jazz is what I play for a living." And saxophone colossus Sonny Rollins said: "The whole idea of jazz is political, because jazz is freedom." You should not ask jazz musicians for a definition of their music. The matter-of-fact answers, although correct, don't tell you anything about the pleasure of creating, the passion for drive and swing, about the cool sensation after a hot session. A lot has been said and written about jazz, often wrong and sometimes stupid. The music was played in bars and brothels, swing was good for dancing jitterbug, and that's why self-righteous conservatives warned against the hellish rhythm that caused the moral decay of young people. Some jazz musicians were on drugs and that's why many fans and critics believed that good jazz was only possible with the help of drugs. And because Sonny Rollins is right, dictators have always banned the music. Now and then jazz was declared...