To judge from the musical soundtracks accompanying this year's political conventions, rock is blue-state music, country is red-state. Gospel is red; hip-hop blue. And disco and soul are, well, kind of purple.

We know this isn't strictly true. People in Idaho and Mississippi, to name two solidly Republican states, probably like the Red Hot Chili Peppers and Black Eyed Peas every bit as much as people in flamingly Democratic states like Massachusetts and Maryland. But those two musical groups were featured performers during the Democratic National Convention in Boston in July. Conversely, twangy country boys such as Travis Tritt and Darryl Worley are not unfamiliar to Upper East Side liberals, but they're being showcased as guitar-strumming good ol' Republicans here.

Indeed, both parties have co-opted pop music genres and artists to market their political messages. The basic idea is to use music to reinforce an affinity with certain voters who are presumed to be fans of each style.

Hence, the conventions have spotlighted a great divide -- the political polarization of pop music.

Republicans are featuring genres that celebrate God and country -- "preachers and patriots," in party parlance -- meaning gospel and country. Democrats, meanwhile, embraced more rebellious styles, especially rock, hip-hop and protest folk.

Check the headliners at this week's Republican convention. Top-billed are Christian singer Gracie Rosenburger, Christian rock band Third Day, gospel singer Donnie McClurkin and Christian pop artist Michael W. Smith. Operatic tenor Daniel Rodriguez, a retired New York City police officer, sang "Amazing Grace."

Then there's the cowboy-booted parade of country performers: Tritt, Worley, Brooks & Dunn, Lee Ann Womack, Mark Chesnutt, the Gatlin Brothers.

You might also hear some Broadway tunes, in a nod to the convention's locale, but there's no hip-hop in the house, no heavy metal, techno, folk, reggae or (heaven forbid!) punk.

Republicans also don't seem to want, or haven't been able to find, a major contemporary rock band. The best they've been able to do is line up a series of "classic" rock bands, all of them with roots in the solidly Republican South. Even at that, these dinosaur rockers -- ZZ Top, Lynyrd Skynyrd, the Marshall Tucker Band, the Dickey Betts Band, .38 Special and the Charlie Daniels Band -- are playing at convention-related parties around town, not on the convention's hydraulically controlled main entertainment stage.

The GOP's musical program was overseen by Frank Breeden, the convention's director of entertainment and a former president of the Gospel Music Association. In booking the acts, Breeden clearly had an eye toward underscoring the convention's setting and its multiple references to Sept. 11, 2001. Rodriguez, for example, gained prominence for his rendition of "God Bless America" after 9/11, and Worley had a hit with the Sept. 11-inspired "Have You Forgotten?"

The Democrats played their own thematic games in July. For those disaffected with President Bush, Patti LaBelle sang "Change Is Gonna Come." Singer-songwriter Carole King crooned "You've Got a Friend" on John Kerry's behalf. U.S. Senate candidate Barack Obama came onstage to a recording of the Impressions' "Keep On Pushing," and Howard Dean exited to Sister Sledge's "We Are Family." Kerry's acceptance speech was bookended by Bruce Springsteen's "No Surrender" and U2's "Beautiful Day," both tunes Kerry uses frequently on the campaign trail.

Popular music has promoted American politicians since George Washington's time, of course, but the current state of affairs bothers Jehmu Greene, president of the nonpartisan Rock the Vote voter registration organization. The political parties have created "a culture clash," she says, that oddly pits rock and hip-hop fans against country fans. "The parties have embraced the music they want to reflect their [voting] bases. Neither one did very much to reach out to another side when they planned their conventions. Music should be a part of healing, but it's being used to polarize."

To be fair to the Democratic and Republican parties, however, the musicians themselves also bear responsibility for this state of affairs. In Boston, Rock the Vote and the Creative Coalition were able to persuade several big-name artists -- such as alternative rockers Maroon 5 and the Red Hot Chili Peppers -- to play at their events. In New York, the reception has been underwhelming; the two organizations were able to secure commitments only from such lesser-known singers as Dana Glover and Angie Stone.

At the same time, the fall campaign season will feature a wave of music-related political activity, almost all of it anti-Bush. In coming weeks, a dozen artists, including Springsteen, R.E.M., Dave Matthews and the Dixie Chicks (along with Willie Nelson, an exception to the country-is-Republican school) will tour battleground states in the Vote for Change concert tour organized by, a liberal group. So far, no one has proposed a pro-Bush tour.

Then there are the albums: "Rock Against Bush, Vols. 1 and 2," put out by the anti-Bush, features Green Day and Sum 41; "Future Soundtrack for America" has recordings by Tom Waits, David Byrne and 20 others; "Wake Up, Everybody" is a new single and album with rappers Missy Elliott, Jadakiss and Eve.

If there's one kind of nonpartisan pop music left, it may be classic R&B and disco. At both conventions, delegates boogied with equal abandon to recordings or live house-band versions of James Brown's "I Feel Good" and other hits from the '60s and '70s by Earth, Wind and Fire, Stevie Wonder and K.C. and the Sunshine Band.

Asked about the politics of his music, Brad Detrick, one of the leaders of the 13-piece band playing at the Republican convention, simply shrugged. "We're a dance band," he said of his group, the Manhattan Rhythm Machine. "We do weddings and corporate events. We play what's popular. We play what people like to hear."

Music that's just entertaining? Music with no political overtones? Now that's a crazy, radical idea.

The Boys Choir of Harlem performs at the convention Tuesday night. The Republicans are using gospel and country for the most part as their signature musical sounds.