Heartless Bastards lead singer Erika Wennerstrom performs at Trees in Dallas Thursday , July 2, 2015.

Heartless Bastards lead singer Erika Wennerstrom performs at Trees in Dallas Thursday , July 2, 2015.

Nathan Hunsinger/Staff Photographer

In mythology, a shapeshifter is a human who magically transforms into another figure. In rock 'n' roll, the closest equivalent is Erika Wennerstrom, the beguiling lead singer of the Austin-by-way-of-Ohio band the Heartless Bastards.

Performing Thursday night at Trees, Wennerstrom changed form almost every time she opened her mouth. One second, her throaty alto galloped and roared like she was Robert Plant of Led Zeppelin; the next, she cooed and oohed in a demure soprano like she was one of the Supremes.

Whenever she needed to recharge, she put her voice into a default Billie Holiday mode, full of stretched consonants and a stark melancholia that fit many of her songs to a T. "I could be so happy if I just quit being sad," she sang. "I could be so funny if I just quit being a drag."

The drummer for Heartless Bastards perform at Trees in Dallas Thursday  July 2, 2015.

The drummer for Heartless Bastards perform at Trees in Dallas Thursday July 2, 2015.

Nathan Hunsinger/Staff Photographer

At times, Wennerstrom looked to the heavens for inspiration. She put down her guitar and lifted her arms to the sky, faith healer-style, as if asking the gods for her next directive.

More often than not, she found the answer onstage, in band mates who were nearly as good at shapeshifting as she was. The Bastards might have sprung from the garage-rock movement of the early 2000s -- they were discovered by Patrick Carney of the Black Keys -- but they've evolved plenty since then, changing members and tackling new styles every few years.

Heartless Bastards lead singer Erika Wennerstrom performs at Trees in Dallas Thursday  July 2, 2015.

Heartless Bastards lead singer Erika Wennerstrom performs at Trees in Dallas Thursday July 2, 2015.

Nathan Hunsinger/Staff Photographer

On Thursday, they skipped over their brief alt-country phase (circa 2009's The Mountain) and focused instead on the folk-rock side of their new Restless Ones CD, which as Wennerstrom noted, they recorded with Grammy-winning Dallas producer John Congleton. The show's high point arrived in its mellowest song: "Pocket Full of Thirst," a soulful new ballad that suggested Emmylou Harris by way of Al Green.

Eventually, the acoustic guitars disappeared and the band shifted into harder material, with bassist Jesse Ebaugh and lead guitarist Dave Colvin striking dramatic poses as the tempo quickened. "Down in the Canyon," from 2012's Arrow, morphed from a Black Sabbath-style dirge into a whirlwind anthem. "New Resolution," from the band's 2005 debut album, crackled with the primal energy of the Ramones. The group ended the show on a bold note, diving out of the blue into a long piece of experimental psychedelia.

"We've got so many albums now, it's hard to fit them all in," Wennerstrom said of the group's five-CD catalog. "All these songs are coming out of the woodwork."

Bring 'em on. If the Heartless Bastards continue to evolve and branch out like they did Thursday night, their future shows are bound to be equally rewarding.

Thor Christensen is a Dallas writer and critic. Email him at thorchris2@yahoo.com

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