The message is instantly statable: there are three kinds of jazz variations. Rhythmic; embellishment of melody, or paraphrase; and those which are new melodies upon famous old chords. (There is also the new ""free form"" jazz in which each musician is independent both of a given melody or chord sequence and of the other musicians.) The point is, if you find yourself facing some totally improvisatory musician, to listen, enjoy and not expect cliches. Williams is currently editing a marvelous Jazz Masters Series for Macmillan. His Pantheon expedition into the heartland of noncomprehension is much less than a marvel. His best squibs are about recording sessions, his best chapter about Horace Silver. He knocks Oscar Peterson, Dave Brubeck and Gene Krupa, all justifiably. His highest praise is for most-mentioned Louis Armstrong, who deserves every word, Monk, Ornette and Miles. There are excellent lists of good records to buy, and a fine chapter on a night at the Five Spot. However, as a writer--here at least-- Williams has none of the qualities he expects from musicians; he is styleless, and worse, not inspiring.