Indigo Girls at Golden State

“I’m sitting underneath that hanging tree, just me and the ghost of the KKK/ Poor man’s gallows in the middle of the woods, the saddest tree that ever stood,” Amy Ray belts out on “The Rise of the Black Messiah.” Anger, urgency and frustration pulse through the electrified guitar riffs.

Ray continues, “My friend I heard you tell of slavery’s end, but have you heard of mass incarceration?/ That old Jim Crow, he just keeps getting born with a new hanging rope for the black man’s scourge.”

The exasperation morphs into hope as Emily Saliers’ voice enters, harmonizing with Ray’s and ultimately yielding the triumph of a gospel choir. While electrified rock isn’t usually common in the Indigo Girls’ work, the song’s theme is characteristic of the longtime Georgia folk outfit. Beyond their songwriting, the Indigo Girls have a reputation for standing behind the disenfranchised and speaking out against injustice.

The duo also has a reputation for building potent harmonies structured on a foundation of contrast. Ray has the voice of a rugged rock and roller, while Saliers is more evocative of classic folk.

After seven gold, four platinum, one double platinum record and several hits like “Closer to Fine,” “Land of Canaan” and “Galileo,” the Indigo Girls’ One Lost Day, released last June, is a collection of some of their strongest work yet. Their first album in four years presents an elegant assortment of history, politics, epiphanies, relationships, life and death.

The touching ballad “Alberta” is the true story of the mining town named Frank, Alberta, which endured a rockslide in 1903 that partially buried the town. On the somber “If I Don’t Leave Here Now,” the duo takes a cue from John Prine as they delve into the dark world of addiction. And One Lost Day’s debut single, “Happy in the Sorrow Key,” was inspired by the death of Ray’s father, who passed two weeks after the birth of her first child.

“A lot of [the album] was influenced by a change in perspective,” Ray told USA Today ahead of its 2015 release.

Ray recorded “Happy In the Sorrow Key” with her guitar plugged into a “bad-ass amp” that she picked up in Seattle. The result is clean grunge in the vein of R.E.M.’s “What’s the Frequency Kenneth” – minus the feedback.

“As I lay my burden down in the cradle of an elegy/ In the shotgun shape of this life I’m happy happy in the sorrow key,” Ray croons.

INDIGO GIRLS 8pm Wednesday, Feb. 17. Golden State Theatre, 417 Alvarado St., Monterey. $38-$64. 649-1070, www.goldenstatetheatre.com