When Bob Dylan sang “The Times They Are A’Changin'” in 1964, he could see an entire generation of Americans changing along with him, a generation that would come to conflate art and politics and define America’s first cultural anti-war movement. Forty years later, the most unpopular American war since Vietnam has stretched into its fourth year. So where is the rock revolution for this war generation?

Hard to find, if you ask many in the music industry today. Perhaps that’s why Rage Against the Machine, the only popular band of the last 15 years to market its heavy political content into mainstream success, has announced its reformation and an upcoming tour. In a consumer era the likes of which Mr. Dylan could not have fathomed in 1964, political activism has plummeted down the totem pole of what sells in pop music. But with national sentiment coalescing into frustration over the Iraq war, that may change.

“I think the times demand that Rage Against the Machine return,” the group’s guitarist, Tom Morello, recently told Rolling Stone magazine.

Still, the question many are asking is, where are all the songs that used to make us feel like we wanted to stand up and fight? Where is Marvin Gaye’s “What’s Going On” or John Lennon’s “Give Peace a Chance”? According to some, they’re still here, just harder to find.

“It’s hard for anybody to be the Bob Dylan of today,” a contributing editor of Rolling Stone, Anthony DeCurtis, said. “Music is much more fragmented today and for one person to have that authority is very difficult. I think you have a variety of people working in different areas instead.”

The days of the AM/FM dial are nearly gone. Popular music is now popular television and popular Internet. Your cable TV offers thousands of channels of music. Satellite radio dedicates each of its stations to specific genres and styles of music, making it harder to stumble across a song or an artist that stimulates or inspires.

Essentially, the “critical mass” no longer exists. In the 1960s and ’70s, the cultural resources for America’s youth were relatively scant; everyone knew Mr. Dylan, Crosby, Stills, Nash & Young, Bob Marley, and Jimi Hendrix. As the baby boomers matured, opinions about Vietnam and America’s role in the postwar world sold records and filled concert halls. Today, that cohesiveness has been splintered, and artists with political views and mainstream aspirations are swimming against the tide.

“There are guys out there with voices and they are being heard in clusters,” the lead vocalist for O.A.R., Marc Roberge, said. “The problem is they aren’t on the radio.”

Most of the songs you’ll hear on mainstream radio today aren’t overtly political, if only because no one has proved that political music sells. The music industry is too busy trying to adapt to the digital revolution and keep kids in record stores to worry about social messages.

In fact, with new bands and labels and blogs popping up every day, there are more musicians writing protest songs today than there were in the 1960s, and those songs are typically more explicit. But these voices are drowned out in today’s hyperactive culture and consumerdriven market.

Neil Young’s most recent album, “Living With War,” was a commentary on Iraq. Bruce Springsteen, another music industry lifer, has written some of his most political songs recently. Elsewhere, acts as varied as the Dixie Chicks and Jay-Z have remained political, sometimes stridently so.

“I think music is important politically, but that idea that somehow one particular song is going to unite a movement, I just don’t see that on the horizon,” Mr. DeCurtis said.

Meanwhile, songwriters such as Steve Earle, who writes explicit anti-war songs, and smaller, more “underground” bands like NoFX and Immortal Technique are screaming to be heard over the drone of mass media.

“There’s just a lot more people around now,” Mr. DeCurtis said. “You have a population that has increased by over 50%. Who’s going to speak to all those people? For one voice to address a mass audience is much harder, especially when you factor in the Internet and everything else.”

And the lack of a draft. Young adults of the ’60s and ’70s had little choice but to involve themselves politically because they could find themselves in Vietnam on any given day. Choices were limited.

“War has been declared against us, but Americans have not been asked to sacrifice,” the president of the Hudson Institute, Herb London, said. “How can the music reflect that? How can you get anti-war music when Americans don’t realize we are at war?”

Indeed, the song that most aptly captures the apathy of this generation may be John Mayer’s recent Grammy-winning single, “Waiting for the World To Change,” on which the 29-year-old crooner sings, “We see everything that’s going wrong / with the world and those who lead it / we just feel like we don’t have the means / to rise above and beat it.”

Enter Rage Against the Machine, who will try once again to spark political outrage in America’s youth and identify the new anti-war generation. It wasn’t easy the first time around: Being a noticeably “revolutionary” musician during the 1990s — a time of relative peace and economic stability — meant going way out on a limb. But today the band, which made it big with songs like “Voice of the Voiceless” and “Vietnow,” may just finds itself riding the next popular wave to the top of the charts.

kherrup@nysun.com