IPSWICH -- A rustic sound, simple and powerful in its joy and earnestness, chimed through the Our Lady of Hope parish hall in Ipswich on the icy afternoon of Dec. 15.

Five voices sat together in a square and harmonized to produce strains, at once robust and ethereal. Tapping their feet to keep rhythm and slicing their arms through the air to conduct themselves, they wove through a medley of Christmas hymns, including "Hark! The Herald Angels Sing" and "Adeste Fidelis."

Their versions of these carols are unlikely to be played on the radio and in shopping malls this time of year. In the wood-paneled, fluorescent-lit parish hall, two Catholics, a Unitarian Universalist, the son of a Baptist preacher, and a Tibetan Buddhist breathed life into a sacred musical tradition that came to the U.S. with the Pilgrims and Puritans. Now, it can be heard throughout the world, on the lips of people of every faith or none at all. It is called Sacred Harp or shape-note singing. On the third Sunday of every month, Our Lady of Hope plays host to an ecumenical gathering in the form of the North Shore Sacred Harp Group, dedicated to preserving and appreciating this unique American art form.

"It's as much social as anything else," singer Bill Holt told The Pilot. "There's a catharsis from singing together. Just experiencing the beauty of singing together, the social bit of being with friends."

Shape-note singing originated in the 1700s, when an influx of new hymns being written in England helped fuel the religious revivals of the colonial U.S. New England's earliest settlers only sang Psalms in church, plus a small selection of traditional hymns, and did so in unison. As more and more hymns became popular, churches began singing multi-part harmonies from songbooks. Shape-note songbooks are so named because they use four shapes to represent the four notes that are the basis of the music -- fa, sol, la, and mi. (Some later shape-note books also use do, re, and ti). Fa notes are shaped like triangles, sol notes like ovals, la notes like squares, and mi notes like diamonds. The name Sacred Harp came from a seminal shape-note songbook of the same name.

"It was designed for people to participate rather than perform, and the focus is on participation, not on making it pretty or performing it to perfection or having a specific style," Holt said.

Holt's father was a Baptist preacher, so he grew up in the musical traditions of various Protestant churches.

He learned about Sacred Harp from his college roommate's co-worker. He has sung Sacred Harp with his friends every Monday night since 1987.

"The Sacred Harp singing, if anything, that's the closest to an ongoing faith community that I have," he said.

Easy to learn and sing, Sacred Harp music migrated from New England to Protestant communities in the Deep South, where it flourished throughout the 19th century. Changing tastes led newer generations to scoff at Sacred Harp as a backwoods relic, until the folk music revival of the 1960s reinvigorated popular interest in the genre.

George Howe, who attends Mass at Our Lady of Hope, has helped introduce Sacred Harp singing to his parish. A shape-note carol, "Voice of the Shepherds," was sung at Our Lady of Hope's Advent Lessons and Carols service on Dec. 17.

"As a member of the universal church, if you will, I find that there is a lot of appeal to it," he told The Pilot.

Howe was raised Unitarian but became Catholic after attending Mass with his wife. It was the music that partly drew him to the faith. He initially wanted to join the folk music group at St. Stanislaus Parish in Ipswich. When that parish was suppressed, he joined the Our Lady of Hope music ministry.

"I certainly have a sense of who I am as part of a community outside of my employment," he said. "I have my sense of who I am as part of a larger faith community."

He heard about Sacred Harp singing from a fellow member of the parish men's group who experienced it at Tabernacle Church in Salem, where the North Shore Sacred Harp Group was meeting at the time.

"George, I think you'll like it," he told Howe at the next men's group meeting.

"He took me the following month," Howe recalled. "I was flummoxed, but I liked it, and I've been coming ever since."

When the group could no longer sing at Tabernacle Church, Howe arranged for them to meet in Our Lady of Hope. Prior to that, they met in the home of Jennifer Revill, herself a Unitarian Universalist. She believes that Sacred Harp singing's growing popularity in recent decades is correlated with the decline in church attendance happening at the same time in the U.S.

"There's a spiritual element to this to many people," she told The Pilot. "And people are finding their spirituality, and this is a place to find it."

Revill likes to find elements of spirituality in the modern world, wherever they happen to be. She discovered Sacred Harp music at the Old Songs Festival in Altamont, New York.

"I heard this weird, odd, discordant style of music," she said, adding: "I'm drawn to it because I love choral music. I'm a choral singer. I'm also into history, and I'm into spiritual matters, spirituality of all kinds. So it suits me that way."

Sacred Harp is simultaneously traditional and unorthodox. All singing is done in a square formation, with the singers facing each other. There is no formal director or choirmaster. Five and six-year-old children can take the lead, guiding toddlers and 100-year-old men in song. Sacred Harp Groups can number from five (as was the case in Ipswich on Dec. 15) to several hundred. Peak attendance for the North Shore Sacred Harp Group is roughly 20 singers. There is no barrier to participation. Song is not recited to an audience but is instead shared freely, like food, drink, or conversation among friends.

"I appreciate that it is organized, but not particularly hierarchical," Christopher Alden Geissler, a professor of linguistics at Boston College and Tibetan Buddhist practitioner, told The Pilot.

Geissler first found Sacred Harp singing in college. It was something that the "cool upperclassmen" were doing, so he joined in order to hang out with them.

"Biologically, we as a species, when we move and sing and chant and things like that together, there's very profound experiences that can happen," he said. "And singing together, particularly in a participatory, non-performative way. It really is a powerful way of transcending the narrow individual experience. And this is a very well-designed, well-honed tool for that."

Geissler carried several heavy shape-note hymnals in his Zabar's tote bag, including "The Sacred Harp" (commonly known as "the red book"). While the songs sung on Dec. 15 were mostly of the jolly Christmas variety, half the songs in "the red book" mention death. Many Sacred Harp songs portray dreary circumstances, providing an unflinching look at the harsh realities of life in the 18th century.

"It's there with a purpose," singer Ron Trial told The Pilot, "to give you an idea about how your life is a short life and you should be prepared."

Trial, a Catholic, has been singing Sacred Harp since 2003, after a friend took him to a gathering of singers. He was a seminarian in Texas for eight years before deciding that the priesthood wasn't for him. He was extensively involved with music at the seminary and sang Mass for the nuns every morning. The songs he sang in the seminary, and the ones he sings with the North Shore Sacred Harp Group, feel similar to him.

"Music itself is an uplifting thing to your soul," he said. "There are things like the 'In paradisum' that is just phenomenal. The effect that that has when you hear it. Most music has an effect that will raise you, or will depress you for that matter."

Trial has made friends from all over the world through Sacred Harp singing. It is an art form that gathers people who may disagree on a multitude of theological or social issues, but the singers do not debate politics or religion. That's not what they're there for.

"When you sit together and sing with others, and you hear the way that harmony sounds, and you work together to make this music, not for an audience, for the group that's assembled," Revill said. "It's purely for you. And that has opened me up to understanding that other people's beliefs and my beliefs don't have to be the same, that we can work together, and then the creation of something very beautiful."