The companion to a PBS documentary miniseries, this unique odyssey plunges deep into the grassroots heart of musical America. Wald, who writes on music for the Boston Globe, and Junkerman, a documentary filmmaker, spent months traveling from the Mississippi's headwaters in northern Minnesota south to the Delta, recording live performances, mingling with musicians, listening to the jazz, blues, rock, gospel, country and bluegrass emanating from 10 states. While FM devotees will recognize some of the acts profiled--Twin Cities band Soul Asylum, gospel choir Sounds of Blackness, New Orleans soul queen Irma Thomas, legendary blues singer Fontella Bass--most of the voices represent what folksinger (and PBS series narrator) Ani DiFranco in her preface to the book aptly calls the ""ever-present undercurrent of organically generated music"" percolating beneath the mainstream of pop culture. There's something here for almost every taste, be it punk rock, Ojibwe Indian powwow songs, traditional Laotion Hmong tunes, blues sessions in Memphis, hip-hop brass band fusion in New Orleans or a Mexican-American band in Illinois playing everything from traditional corridos to the ""Hava Nagilah."" Like the river itself, the book rolls along easily from an annual polka fest in Wisconsin to a zydeco dance hall in Louisiana leaping between commentary, interview segments, memorable lyrics, reminiscences and photographs. Showcasing the richness, vitality, energy and variety of music seldom--if ever--heard on top-40 radio stations, this captivating survey will coax readers to watch the PBS miniseries, which starts in January, and to seek out the accompanying CD soundtrack. (Jan.) FYI: Smithsonian Folkways will release the CD companion to the miniseries in this month.