Helen Bonchek Schneyer, 84, a mesmerizing folk singer who delivered emotionally electric ballads, work songs, African American spirituals and Baptist hymns, died of cancer July 16 at Berlin Health and Rehabilitation Center in Barre, Vt. She had cancer.

She was a nationally known performer who sang at concerts and major folk festivals across the country, as well as in Europe. She shared the stage with many of American's best-known folk singers and songwriters, including Woody Guthrie and Pete Seeger, who urged her at an early age to sing.

Ms. Schneyer, who lived in the Washington area on and off from the 1940s to 1986, was a founding member of the Folklore Society of Greater Washington.

In recent years, Ms. Schneyer was a regular guest on Garrison Keillor's radio show, "A Prairie Home Companion." With her booming contralto voice and imposing stage presence, she belted out songs about the human condition with such power that people felt compelled either to sing along or to flee the performance.

"A lot of agnostics, atheists and people of no particular religions sang about the hope of heaven for the redeemed," Keillor said in an interview. "It was quite amazing for her to perform."

For those who came "looking for something sweet," he added, "Helen was not sweet." Instead, said Keillor, her music "was heart-rending and blood-curdling."

Whether singing such tragic ballads as "Avondale Mine Disaster," or such traditional folk hymns as "Fountain Filled With Blood," or even the somewhat silly "Heaven Will Protect the Working Girl," Ms. Schneyer delivered passionate, heartfelt music. Her deep reservoir of songs transcended eras, from the Civil War through the 1940s, and races -- she loved gospels sang in white and black churches.

By her own account, Ms. Schneyer, who also played the piano, was clear about the nature of songs she chose to perform. In an interview with The Washington Post in 1982, she said: "The only kind of songs that I sing are songs that have some sort of significance for me. I have a lot of trouble singing about kings and queens unless what befalls them is exactly the same thing that would befall me or the janitor."

Helen Bonchek was born Jan. 21, 1921, in New York. From childhood, she studied classical piano, and was drawn at a very early age to the hymns and spirituals of African American Baptists.

"The first music that I remember as a babe in arms was from a black Baptist church in New York," she recalled in The Post. "So it's no accident that I sing so much Baptist stuff. As far as I am concerned, they sing better than anybody because they haven't been shriveled up with good manners in their expressions of their love of God, or fear or hate, or whatever it is."

She was a graduate of the University of Buffalo and received a master's degree in social work from Columbia University during World War II.

After college, she lived in Washington and, with folklorist Alan Lomax, was a member of the Priority Ramblers, singing songs about working and living conditions infused with patriotism. She was with the group when first lady Eleanor Roosevelt invited it to sing labor songs at the White House.

For a time, Ms. Schneyer worked as a psychiatric social worker for agencies in Buffalo and Syracuse, N.Y., before returning to Washington in 1960.

She had a longtime psychotherapy practice in Kensington until 1986, when she retired to Plainfeld, Vt. She continued practicing there until becoming too ill last year.

While in Washington, her home became a focal point for the folk-life community, said Andy Wallace, a longtime friend and a Folklore Society founding member. "We met there, sang there and partied there," and out-of-town entertainers often would stop by, he said. "She was a very important person in the music community in Washington."

In addition to helping found the Folklore Society in 1964, she served on its board in a number of positions, including president. She also was on the board of the National Folk Festival Association (now the National Council for the Traditional Arts).

In 1976, Ms. Schneyer was invited by composer John Cage to participate in a world tour of his bicentennial composition, "Apartment House 1776." As part of that tour, she performed with symphony orchestras in Philadelphia, Boston, New York, Europe and Japan.

A devoted collector of traditional folk songs, Ms. Schneyer conducted a considerable amount of fieldwork in her back yard, said her sister, Mona Masow of Madison, Wis. She would go to black churches in the Gum Springs neighborhood of Alexandria and learn African American spirituals from singers who knew them.

"She was just fascinated with traditional music, the kind that gets passed along from person to person," her sister said.

Ms. Schneyer released three solo recordings, "Ballads, Broadsides and Hymns" (1974) , "On the Hallelujah Line" (1981) and "Somber, Sacred & Silly" (1992). A fourth recording, "What a Singing There Will Be," scheduled for release in August, was recorded in a live concert in Maple Corners, Vt., when she was 82.

She also performed and recorded with her daughter, Ericka "Riki" Schneyer of Takoma Park, and with folk singer Jonathan Eberhart.

Her marriage to Solomon Schneyer ended in divorce.

In addition to her sister and daughter, survivors include a son, Joshua Schneyer of Santa Barbara, Calif.; a brother; and a granddaughter.