No Boundaries for Roots of Philly : Pop: The group’s music, a strikingly original approach to the hip-hop formula, makes it one of rap’s smartest new acts.

Stripped to its core, rap music is free-style, braggadocio rhymes chanted by urban kids who pounded on their desks to create impromptu classroom shows.

The Philadelphia-based rap group the Roots--abandoning contemporary rap staples of drum machines and turntables--has shifted back to that foundation of the old school.

The group specializes in garage-style ‘70s funk laced with up-tempo jazz, with raw break-beats and clever free styles meshing effortlessly with saxophone and piano.

It succeeds even better at letting music take the reins, rather than forcing the fusion, than rap’s strongest rap-jazz fusion to date, Guru’s “Jazzmatazz.”

And with all the commotion about misogyny and violence in rap, it’s refreshing to hear the Roots kick their own rough brand of hip-hop on their debut album “Do You Want More???” Their often nasal rhymes detail days spent chilling in the park with their homeboys (the head-bobbing single “Proceed”) or recount dating woes (the slow grooving “Silent Treatment”).

Drummer Ahmir Khalib Thompson (who goes by the name B.R.O. the R.?) says he doesn’t consider the Roots to be a cross of jazz and hip-hop. The point of the group, he offers, is to prove that black music has no boundaries.

That philosophy shows clearly when the Roots hop on stage, frequently ad-libbing and improvising for more than two hours, with lead rappers Tariq Trotter (known as Black Thought) and Malik Abdul-Basit (Malik B.) dishing out fresh rhymes.

“The key to getting people open to the Roots is time,” Thompson said by phone from Geffen Records’ New York offices. “All they need is 72 minutes of undivided attention.”

Back in 1987, Trotter and Thompson were in high school at the Philadelphia School for the Performing Arts, with such illustrious schoolmates as the future members of Boyz II Men, bassist Christian McBride and jazz keyboardist Joey DeFrancesco. On the roof or in the basement of the school, they would jam until the wee hours in the morning.

Later, they would play for donations on crowded street corners, at family barbecues and in local clubs. Their growing reputation and an independent album, “Organix,” led to a deal with Geffen Records.

“Do You Want More???” reveals a strikingly original approach to the hip-hop formula, with sounds as disparate as Scottish bagpipes and the talents of Rahzel (The Godfather of Noyze,) who goes beyond the “human beat box” styles of Biz Markie and Dougie E. Fresh in imitating a wide array of instruments with his voice. This emphasis on the unorthodox makes the Roots one of rap’s smartest new acts.

“That’s the problem with a lot of rap artists--they feel they have to stay the same,” Thompson said. “The Roots are some brothers who will always push the envelope.”

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The Roots appear with the Watts Prophets on Wednesday at the House of Blues, 8430 Sunset Blvd., (213) 650-1451), 10 p.m. $12.50.