On their last album, 2002's mind-blowing Phrenology, the Roots pushed the boundaries of rap music to genre-bending extremes. On this satisfying follow-up, which takes its title from Malcolm Gladwell's 2000 book about how social phenomena break out, the Philly hip-hop band scales back its approach to its jazz-rap foundation. Born out of jam sessions with guest musicians such as guitarist "Captain" Kirk Douglas and percussionist Frankie "Knuckles" Walker, the new disc has the free-flowing feel of an extended improv at a cool after-hours joint. The CD jumps off with "Star," a cautionary commentary on fame that judiciously samples the 1970 Sly and the Family Stone soul gem "Everybody Is a Star." Elsewhere, the Roots lay down a funky, James Brown-style groove on "I Don't Care," while using horn charts alongside vaguely Middle Eastern flourishes on the chilled-out "Stay Cool." Meanwhile, emcee Black Thought offers up topical political observations on the reggae-tinged "Why? (What's Going On?)" and the R&B-flavored "Guns Are Drawn." A couple of forgettable freestyle raps and a less ambitious scope make The Tipping Point fall short of Phrenology, but the Roots remain true to where they came from.