Writing about music often seems a futile attempt to describe the ineffable, but this engaging primer on jazz appreciation proves it can shed plenty of light. Music journalist Piazza, author of The Guide to Classic Recorded Jazz, writing under the aegis of Jazz at Lincoln Center and with a foreword by its director, Wynton Marsalis, eschews a historical approach in favor of a thematic exploration of the interplay between the mechanics of music-making and their aesthetic effects. He devotes much space to the live improvisatory performances at the heart of jazz, examining the interplay between soloists and accompaniment, the use of chord changes as a harmonic ""understructure,"" the employment of small modular ""choruses"" like the 12-bar blues format to build up larger musical structures, and the mystery of how jazz ensembles fuse spontaneous individual improvisations into a coherent musical whole. Piazza's lightly intellectual approach adds a dash of music theory and formal aesthetics. But he keeps his explanations limpid and straightforward-his chapter on swing rhythm is something of an expository tour de force, based on the simple but revealing analogy of a child on a playground swing-and leavens them with lyrical meditations on the subjectivity of time and storytelling in jazz. Like all prose, his cannot quite capture the emotional impact of music. Fortunately, the book is accompanied by a CD with illustrative classic recordings, which Piazza analyzes in sometimes second-by-second exegeses. His extensive discography of the recorded jazz canon, taking up over a third of the text, provides a further guide for neophytes wishing to move on from this wonderful introduction. Photos.