Musicians using their voices to raise awareness for a noble cause is nothing new. A bunch of stars from the Twin Cities music scene, however, are using nothing but their voices to fight sex trafficking in Minnesota.

Haley Bonar, Dessa, Chris Koza, Robert Robinson, Charlie Parr, Prairie Fire Lady Choir and John Hermanson are among the noteworthy local music-makers who contributed vocals-only recordings to a new benefit CD, “Voice: Songs for Those Who Are Silenced,” intended to raise money and awareness for the Women’s Foundation of Minnesota’s “Girls Are Not For Sale” campaign.

Unless you count finger snaps or hand claps, not a single musical instrument is heard on the album over the course of 18 songs.

The end result is one of the more captivating, inventive local albums of the year — chilling at times, serene at others, always with a deep backbone of emotion. There seems to be something stronger about singers doing their thing without any instrumental support.

“We are so honored to be singing our song in its purest and most vulnerable form to give a voice to the voiceless,” said Jenny Kapernick, who sings alongside her sister Bethany Valentini as the Ericksons.

The Ericksons are one of six acts on the album scheduled to perform at the “Voice” release party Sunday night at Bedlam Lowertown Theatre in St. Paul. Also on the bill are We Are the Willows, Hermanson, the Prairie Fire choir and spoken-word pioneer Shá Cage with singing partner Jayanthi Kyle of Black Audience.

The latter duo’s composition, “Not For Sale,” is the album’s dramatic apex, written specifically for the project about a young victim forced into prostitution. “Breathtaking,” is how “Voice” organizer Kriss Zulkosky aptly described their track.

A nurse by trade, Zulkosky came up with the idea for the project three years ago after realizing that “even among a lot of my well-informed, intelligent and caring friends, sex trafficking was not on most people’s radar as an issue.”

The issue of underage prostitution and trafficking in Minnesota has since been better spotlighted by the Women’s Foundation’s campaign and by media outlets. Minnesota’s Sen. Amy Klobuchar and Rep. Erik Paulsen each championed bills in Congress this year to improve trafficking enforcement.

Zulkosky did her part simply by “calling as many musicians and musicians’ managers as I know and simply asking,” she said, a tactic she credited to her husband, Chris Larson, a musician and ringleader of the House of Mercy music organization.

“An overwhelming majority of them said yes,” Zulkosky said, “but I had no idea the idea would turn out as well as it did.”

For musicians who are mostly used to working with electric guitars, drums and other loud gear they can hide behind, the challenge of stripping back and working solely with their own pipes was a nice byproduct of supporting the cause any way they could.

“Most of them were a little nervous at first to put themselves out there like that,” said Joe Mabbott, a prominent engineer/producer who donated his services and helmed sessions at his northeast Minneapolis recording studio, the Hideaway. (Hermanson did the same with his Egg Music studio.)

“Once they settled in, they got comfortable with it and really owned up to their voices like never before,” he said.

The one exception, he added, was gospel vet Robinson, “who was nonchalant about it and nailed it right away.”

Several acts sang their tracks purely a cappella, including the Ericksons, Zoo Animal’s Holly Hansen and Texas alt-country star Carrie Rodriguez, the only out-of-towner on the project. Many participants layered different vocal parts on top of one another, such as Koza, who hummed a repetitive bass note for accompaniment.

Koza said he loved the challenge: “To create a song that could stand alone without any other supportive instrumentation? That’s where I had to be creative.”

He also thought outside the box with his song selection, choosing a 100-year-old local gospel tune, “By the Waters of Minnetonka.”

A lot of other acts chose original songs they already written that suited the project. Dessa let them use an a cappella track, “Poor Atlas,” from her “A Badly Broken Code” album. The Ericksons went with “One Heart,” which Kapernick said is “a song of ours with the most simple, loving and pure message.

“I can remember when Bethany played it for me for the first time. I just sat in a chair and cried. Simple, beautiful music can strike a chord so deep.”

That could be said of the entire album.

A limited number of copies of the “Voice” CD will be sold at Sunday’s show with hand-stamped artwork by Hamilton Ink Spot, a printing studio in downtown St. Paul. Starting Tuesday, the album will also be available for download via iTunes.