Eric Salzman, associate music critic of the late New York Herald Tribune, has written an introduction to twentieth century music that shouldn't put off any interested party, which, in view of the complexity of the subject, is saying quite a lot. He has accomplished this by simplifying to a single theme, the evolution of tonality, from earlier to contemporary music. It is a theme with variations: the awareness and mention of other musical elements such as rhythm, for example. While twentieth century music has its roots in what came before, it also has a ""pervasive unity that distinguishes it from its past"" based on the breakdown of traditional tonality. Mr. Salzman inspects first the ""functional tonality"" of the period from 1600 to 1900, turns then to its dissolution in the nineteenth century (Wagner's chromaticism), the revolution in Paris (Debussy, Le Sacre du Printemps), Vienna (Schoenberg, Berg, Webern). He then explores Stravinsky's neo-classicism, movements outside France and in other nations, in musical theatre; the vanishing scale and the diffusion of Schoenberg's twelve-tone scale. Finally, he reviews the avant garde: its sources, ultra-rational and electronic music, anti-rational and aleatory music, the newly performed music. Less analytical than the Machlis Introduction to Contemporary Music (p. 761, 1961) in that it does not offer full technical analyses of representative pieces but instead offers an overview, this is an extremely readable ingathering of information that should be attractive to the average music lover. As an introduction, it performs very-well indeed.