Living up to the “true spirit-child of Woody Guthrie” label would be harder if Pat Humphries was a lone voice for social justice.

But she and Sandy Opatow (Emma’s Revolution) are part of a tradition that Guthrie, Bernice Reagon (Sweet Honey in the Rock), Joan Baez, Holly Near, Phil Ochs, Pete Seeger, Tom Paxton, Janis Ian, and Peter, Paul and Mary.

Emma’s Revolution performs Oct. 15 in Shoreline.

Humphries and Opatow have performed together periodically for a dozen years but have sung as a duet full-time for three years. They’ll perform songs from their album, “one x 1,000,000 = change.”

“Using music as a vehicle to gather people around issues, not only to articulate what’s going on in our culture but also to bring people to a deeper understanding, and to refresh and revive people when they’ve been beaten down … is not a new thing,” Humphries said.

“Some believe that I’ve had some modest success at doing a similar thing, helping people see themselves in some of these larger political issues … making people feel empowered, stronger and more able to endure but make things better for generations coming up,” Humphries said.

Their talents would earn them more money if they wrote catchy pop songs, but that’s not the path they’ve chosen.

“So many are writing songs about personal relationships or flirtation, really, scads and scads of people, and that’s a small percentage of people’s lives,” Opatow said.

Instead, Emma’s Revolution performs at many events that are organized around issues (peace, poverty, abuse of women, gay rights, sweatshops).

“When you’re willing to dig that deep into your own issues, you get to that kind of essential human place where other people relate to the struggles,” Humphries said.

One song that has made the rounds is “If I Give Your Name,” which won the grand prize in the folk category at the 2003 John Lennon Songwriting Contest. It was inspired by the plight of undocumented workers killed in the World Trade Center attack.

It was their first co-written song.

“We were so shaken by the invisible part of the work force and all their family members, in their own silence, while having almost no recourse to address their grief and the needs of the family,” Humphries said.

For the folksinger-as-activist, music is an instrument of change.

“There is no social movement (that) has not had a significant cultural component. Name three speeches from the civil rights moment; try to stop at three songs from the civil rights movement,” Humphries said.

“Not that these other expressions aren’t extremely important but music does a certain kind of work in the culture. It’s a way in which advertisers are well aware of, the power to encourage people to buy the products they sell.

“We use it all the time to placate, to affect public opinion whether we call it political or not. It’s affecting people’s world view,” Humphries said.

Emma’s Revolution’s songs are carried by people from march to gathering, campfire to rally, concert hall to peace caravan, without the support of a major record label or extensive airplay.

Like Pete Seeger said, “It’s hard to stop a good song.”