Twenty years after Live Aid, a new humanitarian concert extravaganza called Live 8, featuring a star-studded lineup that includes U2, Coldplay and Paul McCartney, is ready to hit stages across the world

Once again, the stars are coming out to support a cause. This time it’s the Live 8 global pop-music concert extravaganza, in nine cities on Saturday, that seeks to galvanize public support for combating African poverty. The shows will feature such performers as U2, Coldplay, Paul McCartney, Stevie Wonder, Pink Floyd, Madonna, Jay-Z, Tim McGraw and Sheryl Crow.

They come 20 years after Live Aid, the all-star benefit shows in Philadelphia and in London that raised $180.7 million (in today’s dollars) to aid African famine relief.

Both productions are in the long show-business tradition of involvement in humanitarian, social and political issues, from helping workers organize to helping candidates get elected.

In addition to raising money, raising awareness is the goal of any benefit show, says rock ‘n’ roll historian Glenn Gass of Indiana University.

“Before Live Aid, people hadn’t given Africa a second thought,” Gass says.

“It’s wonderful to see artists stand up for what they believe in and act as cultural leaders,” says Carolyn Mugar, executive director of Farm Aid, which runs the annual concerts founded by country star Willie Nelson in 1985 to assist family farmers.

The idea was hatched on the Live Aid stage in Philadelphia in 1985, when Bob Dylan asked the crowd, “Wouldn’t it be great if we did something for our own farmers right here in America?”

Since then, co-founders Willie Nelson, John Mellencamp and Neil Young have testified before Congress on behalf of family farmers and have hosted an annual concert in various venues (the specifics of this year’s show have not yet been announced). Their efforts have raised more than $26 million.

Farm Aid has a board of directors and a paid staff of nine. It no doubt learned a lesson from the Concert for Bangladesh, the 1971 benefit organized by former Beatle George Harrison to raise money for the millions made homeless after a killer flood tore apart the South Asian country.

Billed as George Harrison and Friends, 75 artists rocked Madison Square Garden. Though the concert was a success, spawning an album and a documentary film, problems ensued because Harrison had failed to set the show up as a charitable organization. It took a team of tax lawyers 11 years to finally release the $64.8 million raised to UNICEF, the designated charity.

Nevertheless, says Robert E. McQuiston, a Philadelphia lawyer who worked to untangle the mess, the Concert for Bangladesh was a success “because it was the initial signature concert promoted by (rock stars) for the benefit of charitable causes. And it’s still influencing everybody today.”

The power of stars to bring in big bucks was demonstrated just 10 days after the Sept. 11, 2001 terrorist attacks. Major show-biz figures gathered in New York and Los Angeles, raising $164.7 million in pledges during the “America: A Tribute to Heroes” telethon.

After “Tribute” came a plethora of 9/11 benefits. Last year, the high-profile Vote for Change tour that raised money for the Democrats featured the Dixie Chicks, R.E.M., the Dave Matthews Band, Pearl Jam, James Taylor and Bonnie Raitt.

The headliner was Bruce Springsteen. He had sung for many causes, including the 1979 No Nukes concert and the 1985 all-star “We Are the World” record that raised $113.8 million for African famine relief, but he had never before openly campaigned for a candidate.

Still, historian Gass thinks young people are starting to turn a deaf ear to concerts featuring older-skewing acts.

“I sense my 20-year-old students saying, ‘I don’t want to deal with this. This is not my problem,’ ” Gass says. Those students, who started college just before or after 9/11, are “beleaguered by the (2004) election and pretty much tuned out,” he says.

Live 8 organizer Bob Geldof certainly hopes not. One unusual aspect of his free shows with unpaid performers is that they aren’t meant to raise money.

He hopes Saturday’s concerts in Philadelphia; London; Cornwall, England; Paris; Rome; Berlin; Johannesburg; Tokyo and Toronto, plus a July 6 show in Edinburgh, Scotland, will mobilize public opinion by shining an international spotlight on a human problem.

“This is not Live Aid 2,” the former Boomtown Rat says on the Live 8 Web site (www.live8live.com). “By doubling aid, fully canceling debt, and delivering trade justice for Africa, (world) leaders could change the future for millions of men, women and children.”

“It’s what artists have always done – comment on society and raise awareness,” Gass says.

“The question to ask is, ‘Are you an artist or an entertainer?’ Because artists do more than entertain.”