When thousands of people marched in Washington last month to protest the war in Iraq, Joan Baez serenaded them on the National Mall with "Where Have All the Flowers Gone?"

At a march in San Francisco the same day, a protester with an iPod and speakers pumped up the crowd with Edwin Starr's "War." When Starr growled: "War — huh! — What is it good for?" The marchers answered, in unison: "Absolutely nothing!"

Marchers in other cities resurrected John Lennon's "Give Peace a Chance."

Let's review.

"War" hit the charts in 1970. "Flowers" goes all the way back to 1956, when Pete Seeger wrote it after appearing before the House Un-American Activities Committee, but it became a hit when Peter, Paul and Mary recorded it in 1962. "Give Peace a Chance" dates to 1969.

Those songs, and dozens of others, provided the soundtrack of the baby-boomer generation's coming of age. They gave young people in the 1960s and '70s a way to respond, collectively and emotionally, to a war that was sending young men off to Southeast Asia and taking the lives of more and more of them.

The summer after the Kent State shootings in May 1970, everyone heard the drumbeats. "Woodstock," the documentary, had come out in March. Anti-war singles were getting heavy rotation on FM radio. The music was mainstream enough in American culture that even middle-aged parents knew some of the lyrics.

By the end of the '70s, the war in Vietnam was over, and most of the songs had collected their AARP cards and moved to Florida. Their work was done. They popped up occasionally on an oldies-but-goodies radio station or perhaps as background in a movie set in the '70s.

Now these old songs are back for real, providing the soundtrack to marches against a different war.

So why are protesters today singing songs from 30 years ago?

It's not that young musicians aren't writing anti-war songs or that people under 30 aren't listening to them. Plenty of songs are out there if you know where to look: "Deja Vu (All Over Again)" by John Fogerty, "The Price of Oil" by Billy Bragg, "Son of a Bush" by Public Enemy, "Idiots Are in Charge" by NOFX, "Why?" by Jadakiss.

The key phrase is "if you know where to look." One place not to look is mainstream commercial radio, which has grown increasingly conservative as it has consolidated into just a few corporate owners.

Clear Channel Communications, the largest corporate radio conglomerate with more than 1,200 stations, caused a stir after the Sept. 11 terrorist attacks, news outlets reported, when it sent its stations a list of more than 150 songs it said were potentially offensive. The list included John Lennon's "Imagine,"

Cat Stevens' "Peace Train" and Simon and Garfunkel's "Bridge Over Troubled Water." After widespread criticism, the company backed down.

Still, except for Green Day's Grammy-winning "American Idiot," an ambitious punk-rock opera about living in a fear-driven America after Sept. 11; Eminem's "Mosh"; and Bruce Springsteen's "Devils and Dust," not many anti-war songs have really hit the mainstream. If you want to hear them, you have to tune to college and satellite radio stations or hit the Internet for downloads. Bands say they can't get record labels to back them.

Another factor in the lack of march-worthy protest songs is that styles of music have changed. In the 1960s and '70s, new music was dominated by folk and folk-rock music, performed by singer-songwriters who put their values and views into their music. Today, the music scene is dominated by manufactured pop acts, their songs created in the studio by powerful producers and songwriters-for-hire.

For political and protest music, you have to look to a few rap and hip-hop artists and the punk scene. Fat Mike of NOFX was the driving force behind "Rock Against Bush," a compilation CD released in April 2004 with contributions from the likes of Alkaline Trio, Sum 41, Anti-Flag and the Offspring. Fat Mike is also behind punkvoter.com.

Of course, distribution problems are hardly the only reason for the lack of a groundswell of new political music. The Punk Voter and Vote for Change tours last year were not as successful at galvanizing the college and youth vote as the organizers had hoped. Perhaps these movements are just playing to a figuratively empty stadium.

Why? One theory holds that the Vietnam-era draft was what really inspired the anti-war movement back then; without a draft to spur them, most of today's young people just don't care.

A close relative to that theory holds that college campuses, once hotbeds of political activity, have turned into veritable vocational schools, churning out MBAs interested only in careers.

Another theory says that America is only two years into this war and that protests against Vietnam did not accumulate critical mass until far later in the game. And a final theory says that America is simply more conservative now.

Promoters of this theory point to the Republican ascendancy and to the success of such pro-war songs as Toby Keith's "Courtesy of the Red, White and Blue" and "American Soldier," Clint Black's "I Raq and Roll," and Darryl Worley's hit, "Have You Forgotten." These are the 21st-century analogs of Barry Sadler's 1966 hit, "Ballad of the Green Berets."

Will the protesters of 2030 be marching to the tune of "American Idiot" or "American Soldier"? Who knows? Just so long as an 89-year-old Joan Baez doesn't have to croak yet another rendition of "Where Have All the Flowers Gone?"