Taking It To the Streets: Audioslave/Rage Against the Machine guitarist Tom Morello returns to rap-rock with Coup frontman Boots Riley in Sweet Sweeper Social Club

A generation ago, it would have been an odd pairing: a Marxist rapper in cahoots with Rolling Stone's No. 26 on its list of the Greatest Guitarists of All Time. But popular music has changed since guitarist Tom Morello literally shook the earth with his seminal rap-rock band Rage Against the Machine. (A bouncing crowd at 1994's Pinkpop Festival registered a 1.1 on the Richter scale.) After stints in platinum rock band Audioslave and unplugged solo project the Nightwatchman, Morello is once again raging like Rage with new band Street Sweeper Social Club, which is fronted by Boots Riley.

Street Sweeper got the pit jumping on this summer's Nine Inch Nails/Jane's Addiction tour. And for Riley, whose group the Coup has been playing clubs for fifteen years, it was a whole new world.

"I was worried it would be a bunch of folks in all black, looking like Edward Scissorhands with black fingernails, with their arms crossed, mad that Trent Reznor wasn't onstage," Riley says. "And that's not what they were like, and that's not what they look like. [It was] the best tour I've even been on; the biggest crowds I've ever rocked."

Morello — a Harvard-educated hip-hop fan, activist and holder of similar political inclinations — called Riley out of the blue in 2003, to invite him on Billy Bragg's Tell Us the Truth tour. Riley didn't know Rage's music well, but knew of the guitarist: A friend had given the rapper a Guitar World interview in which Morello talked politics, and the ax man seemed like his kind of guy. On tour, Morello backed Riley, playing acoustic guitar while the rapper spat Coup songs. When Riley saw the video for Audioslave's "Cochise," he was impressed.

"I hit [Morello] up and said, 'I didn't know you'd be coming that funky with the riffs,'" recalls Riley.

They kept in touch. Eventually Morello gave Riley a cassette of acoustic riffs, told the rapper he was now part of a group called Street Sweeper and told him to "do what you do" — write some lyrics. Morello later electrified the music into metal-plated funk, playing both guitar and bass on the album.

Street Sweeper's self-titled full-length debut has more to satisfy Rage fans than anything Morello has done since. It handily out-rocks Rage's curiously limp last original album, 1999's Battle of Los Angeles. Nevertheless, Riley and Morello's mental harmony doesn't always translate into the music. At its low points, Street Sweeper Social Club sounds like a poorly produced mashup: Although Morello is far better suited to groove than Audioslave frontman Chris Cornell, Riley's dexterous flow doesn't always quite sync with the guitarist's clenched-fist riffage.

The political messages can also be more slogan than manifesto; critic Dan LeRoy called it "jock jams for flag burners." But shout-along choruses such as "Alright, motherfuckers/Let's fight, motherfuckers" (from "The Oath") have a way of sticking in your head. Similarly, the upcoming single "Promenade" seems awkward on initial listens, but has an insidious quality.

"What I said to [Morello] is, we need to have our version of [Queen's] 'Another One Bites the Dust,'" Riley explains. "The whole song is a macabre square dance that parallels our political struggles. I actually wrote it to the beginning of [the White Stripes'] 'Seven Nation Army.' The idea was for it to be a rock-funk-disco square dance. Whatever else you say about it, it's something Tom Morello has never done in another band."

Live, Riley says Street Sweeper Social Club will continue to play most of the album, along with some Coup songs, but no Rage material (since Rage has re-engaged as an active band). Another album will follow.

Riley's veteran presence may technically qualify the group as hip-hop — as opposed to rap-rock, a term that usually evokes Limp Bizkit and a thousand bro-hard emulators. The most critically derided genre always sparks lively semantic discussions.

"You can call it rap-rock," says Riley. "It's kind of hard to say it's a straight hip-hop record. It's made like a rock record. And it has a rapper on it. I don't care what someone wants to call it. Listen to the record."