The title of the Roots' fifth studio album comes from Malcolm Gladwell's 2000 book The Tipping Point: How Little Things Can Make a Big Difference, which was about the critical moments that touch off social phenomena and how "messages and behaviors spread just like viruses."

The Philadelphia collective led by drummer and producer Ahmir "?uestlove" Thompson has been agitating for change in hip-hop for a dozen years now, calling for more musical innovation and a stronger message of social consciousness. The Roots' uncompromising values have won them a reverential cult following, but mass popularity has eluded them. Clearly, Thompson, who describes this disc as a summation of everything the group has done to date, is hoping that this is the group's tipping point.

In fact, while the album is stronger than 2002's "Phrenology," it falls a bit short of 2002's "Things Fall Apart," which remains the band's masterpiece. But on tracks such as the opening "Star," "Somebody Gotta Do It" and the epic closer "Melting Pot," the Roots maintain their reputation as one of the most diverse and creative groups in modern hip-hop or R&B, creating a "virtual duet" with Sly and the Family Stone on a reworked version of "Everybody Is a Star" at one moment, and evoking a cross between John Coltrane's Quartet and Parliament-Funkadelic the next.

Meanwhile, rapper Black Thought (Tariq Trotter) serves as a powerful focal point -- he is significantly underrated for both the style and the substance of his raps. He also gets some prestigious assistance here from several guest MCs, including Jean Grae and comedian Dave Chappelle.

Jim DeRogatis

*** 1/2  THE POLYPHONIC SPREE, "TOGETHER WE'RE HEAVY" (HOLLYWOOD)

The 25-member Dallas mini-orchestra has been dismissed by some critics as a novelty act, and there is a fair amount of shtick in the Polyphonic Spree's live presentation. Musicians clad in white robes play everything from theremin to tympani and French horn to Moog synthesizer while evoking some odd combination of the Beach Boys circa "Pet Sounds," the "sunshine pop" of early '70s bands like the Association and the Fifth Dimension and the post-hippie "God rock" of "Godspell" and "Jesus Christ Superstar."

None of it would hold up, however, if it wasn't for the strength of bandleader Tim DeLaughter's songwriting. The band's second album represents its first proper crack at the recording studio, and it's a big leap forward from the independently released "Beginning Stages of... The Polyphonic Spree." Irresistibly catchy, giddily optimistic and fleshed out with the group's absurdly ambitious ork-pop arrangements, tunes such as "We Sound Amazed," "Two Thousand Places" and the title track ultimately succeed because under all the filigree, they're great pop songs. And there's nothing novel about that.

Jim DeRogatis