Hip-hop has had 30 years to penetrate the national bloodstream, and our cultural guardians have spent much of that time trying to adapt the form to the musical narratives that span from jazz and blues to rhythm and blues, soul music, funk and rock 'n' roll. Most of these were well-intentioned efforts and, almost without exception, got the story halfway wrong: in hindsight, hip-hop's collage-based aesthetic seems more like a radical break from the blues . idioms that dominated popular music in the previous century. But in a deeper sense the comparisons ring true: The blues emerged during Jim Crow, transcended its local origins, and morphed into every corner of the globe. Hip-hop made its way through the rubble of the South Bronx of the 1970s to become the international phenomenon it is today. Both forms represented the end of stalled political processes (Reconstruction and the failures of Lyndon Johnson's Great Society, respectively); each has involved great rechannelings of creative energies, and each has come to serve as a model for social change, both here and abroad. Jeff Chang's history of what he calls "the hip-hop generation" takes this model as its starting point - it is less a history of music than a documentation of the cultural movement inspired by music, as well as an attempt to define "hopes and nightmares, ambitions and failures” of a generation whose only unifying characteristic may be its opposition to any definition an outsider might impose. This is a damn difficult project, but at least in the beginning the movement was so small, and so site-specific, that Chang finds it easy enough to narrow it down: "It might be hard to imagine now, he writes, "but dur... halfway through the paper...remain to hold the hip-hop generation together." (In the words of graffiti writer and activist Chang quoted approvingly, "Young people are noticing that the one thing that can no longer be bought, sold, co-opted or commercialized is substantive political organizing and dissent.”) Whether or not this is true – and I have met some politicians who argue this point – it makes you wonder what today's young people should be organizing for or dissenting against. Is it the World Trade Organization? Police brutality air at the 2000 Democratic Convention), I couldn't, for the life of me, figure out what they were protesting. Even I wasn't sure if anyone present knew.