The crowded room echoes with lilting voices raised in a simple, timeless song. There are no instruments, no audience. Just a chorus of four-part harmonies sung from a book that’s as thick as a Bible.

Each Tuesday, dozens of people — young women with nose rings and neon-colored hair, graying baby boomers, hipsters in beards and plaid shirts — come to this room in the University Baptist Church in Minneapolis to take part in one of the oldest forms of American music, known as shape-note singing.

“There’s something very different about this,” said Joel Menk, 26. “Everybody’s just singing for each other and this communal experience of singing together. … The focus is about putting your heart into it and singing it loud — really belting it out.”

This a cappella style of singing dates to the country parishes of England early in the 18th century. Colonialists brought the tradition with them to the New World, where the music quickly spread from churches and schoolrooms across New England to the rural enclaves of the American South.

But the tradition, which had its heyday before the Civil War, declined swiftly as small towns dwindled, church attendance slipped and Americans gravitated toward more modern forms of music.

Now a new generation of younger singers is helping to fuel a renaissance of the centuries-old singing style in Minnesota and around the nation.

“In many ways it feels like the vision I had 10 years ago is finally coming into fruition,” said Kim Bahmer, 33, who started the Tuesday night “singings” at the church in Dinkytown when she was a music student at the University of Minnesota.

“I noticed there weren’t any folks my age singing in the local community, and it was intimidating to sing with people so much older than me,” she said.

At first, only a handful of fellow U students showed up to Bahmer’s singings. Then, “a few years back, this wave of young folks seemed to be pouring through the doors,” she said. “And it continues.”

All ages of singers now flock to the group, and other groups meet on Sundays at various locations around the Twin Cities area and in Duluth.

The music is mostly sacred, but it includes some secular folk hymns, odes and poems — all covering the age-old subjects of sin, doubt, fear, death, judgment and salvation. Melodies sometimes come from traditional ballads and dance tunes.

But the raw harmonies and ancient customs have proven to be a powerful draw for Gen Xers and millennials.

“I walked into a room and my life changed,” said Alec Jenkins-White, 28, of St. Paul. “I was just transfixed.”

Growing up, Jenkins-White sang along with Johnny Cash records and took a liking to a scratchy recording of a tune that he found out later was a shape-note song.

Several years ago, he showed up at a national shape-note convention at the Union Depot in St. Paul, and ended up singing until the sun came up.

“I liked the idea of singing in a community with my friends, but I didn’t have a good venue for that,” he said. “I wasn’t a member of a church where that usually happens. I found shape-note singing, and it was the full package.”

That sense of community hooked 28-year-old J.R. Hardman, as well. She discovered shape-note singing about four years ago, hoping to impress a guy who invited her to a gathering.

“I just got sucked in,” said Hardman, who grew up in Woodbury but now lives in Atlanta. “The first time, I was singing all night long. And it was almost all young people. I had no idea what was going on, but it didn’t seem that hard because people were so excited to show you what to do.”

Power in ritual

The name for this form of singing comes from the notes, which are arranged on sheet music in the traditional way, but are represented by four shapes — a triangle, circle, square and diamonds. Early teachers thought that the shapes would make it easier for children and groups of people to sight read.

There’s also a distinct ritual. The first time through a song, singers don’t use the words, but voice the notes as “fa,” “sol,” “la” and “mi.” The song leader and key members of each section keep tempo by making a chopping motion, while others may tap their toes or keep the beat with an open palm or pointed finger.

Singers arrange themselves into four groups — the alto section faces the tenors, and the bass singers face the trebles. In the middle is the sanctified “hollow square,” where the song leader stands, taking on the full brunt of voices and the balance of the harmonies.

“There’s nothing like the raw power of standing in the center of the square,” said Matt Wells, 49, a leader of the Twin Cities shape-note singing organization. He claims ancestral heritage to Benjamin Franklin White, a west Georgia native who co-authored a version of “The Sacred Harp” tunebook in 1844 that is widely credited with spreading shape-note singing across America.

Because of the popularity of that songbook (and others with the same name), shape-note singing also is commonly called Sacred Harp singing.

While many of the songs are Protestant hymns, shape-note enthusiasts say the music stretches well beyond its Anglo-Saxon roots.

“We are young, old, conservative, liberal, every religion you can imagine,” said Jane Wells, Matt’s mother. “We have Jews and Hindus — it’s not just Protestants and Catholics.”

Singing with heart

Minnesota wasn’t even a state when shape-note singing first took hold in the U.S., but it’s on the map of the music’s revival. Shape-note groups have been springing up here since 1990. There are several national gatherings, known as conventions, held here each year, and the Minnesota mailing list has about 500 names.

University of Minnesota musicologist and musician Tim Eriksen helped spark the rebirth, as a teacher and with his work on the soundtrack of the 2003 Civil War movie “Cold Mountain.”

Still, this style of singing and the rituals that go with it remain on the fringes. Younger shape-note singers are a passionate lot, however, and they want to do their part to give shape-note singing a hopeful future.

“It’s this still living, breathing, singing community,” said Menk, who first heard one of the folk hymns with “this weird sound to it” at a concert of world music last summer. “It just captured me.”

He also sings in a choral group, where the focus is on technique and performance. While he enjoys that discipline, he said, it’s nothing like the ebullient, full-on approach of shape-note singing.

“Here,” he said, “it’s all about putting your heart into it.”