Season 4

Rooted in New Orleans's rich music culture, No Limit mogul Master P and bounce breakouts DJ Jimi and Juvenile shake rap and put twerking on the map.

Innovators explode out of the South: Houston's DJ Screw slows hip-hop down, Memphis's Three 6 Mafia goes dark, and Atlanta's Lil Jon brings the crunk.

Auteurs like the Neptunes' Pharrell and Chad expand the sonic palette. Timbaland and Missy Elliott lean forward. Kanye West and J Dilla reimagine rap.

Mixtapes spread the hottest sounds, infringe copyright and break artists. Among them, 50 Cent polarizes, T.I. takes off with trap, and Lil Wayne clicks.