Delois Barrett Campbell, whose bell-like soprano helped define two world-renowned gospel groups, the Barrett Sisters and the Roberta Martin Singers, died Aug. 2 at a hospital in Chicago from a pulmonary embolism. She was 85.

Mrs. Campbell, a minister’s daughter, was a teenage standout on the church circuit in her native Chicago. She soon became a featured performer with the Roberta Martin Singers, a pioneering gospel outfit known for its leader’s innovative piano work and its emphasis on vocal soloists.

While maintaining her prominent role with Roberta Martin, Mrs. Campbell also embarked on a long singing career with her younger sisters Billie Barrett GreenBey and Rodessa Barrett Porter. The sisters achieved greater prominence in “Say Amen, Somebody,” George T. Nierenberg’s acclaimed 1982 documentary about Chicago gospel legends.

Reviewing the film, New Yorker movie critic Pauline Kael described the sister trio as “dramatic, physically striking women with ample figures in shiny, clinging blue gowns.” She said that they “sing so exhilaratingly that they create a problem” by dominating the film with their powerful vocals.

Gospel music scholar Anthony Heilbut said that, as a soloist, Mrs. Campbell “had a voice of many colors, capable of dazzling blue notes. She could have brought that magical phrasing to pop music if she chose to.”

Deloris Barrett was born March 12, 1926, on Chicago’s South Side. She later changed her name to Delois (pronounced “duh-LOIS”). Her father was a deacon at Morning Star Baptist Church, and her mother sang in the church choir. A brother and three of her sisters died of tuberculosis during childhood.

In the 1930s, Chicago’s South Side was the epicenter of the burgeoning gospel musical style. The Barrett family’s neighbors included noted gospel songwriter Thomas A. Dorsey, author of “Precious Lord, Take My Hand,” and revered gospel singer Mahalia Jackson. Delois once recalled that Jackson told her she had a voice that “opened up like a rose.”

In 1941, Delois married the Rev. Frank Campbell. At the time, she was performing regularly at her father’s church with her sister Billie and a cousin. She was soon recruited to Martin’s group.

Mrs. Campbell first recorded as a soloist on the 1947 Martin recording of “Yield Not to Temptation” and continued to work with Martin’s group into the mid-1960s.

In 1963, she began performing professionally with her siblings as the Barrett Sisters. Martin accompanied them on piano when they first appeared on Chicago’s “Jubilee Showcase” TV program, lending her well-established imprimatur to the group. That year, the Barrett Sisters recorded the first in a series of recordings for Savoy Records, “Jesus Loves Me.”

“We didn’t use any written music,” Mrs. Campbell told the Chicago Tribune about her approach to performing. “It all came from the top of our heads. We would sing it one way today, and the next day, we would make it something else. You’re constantly building on a song.”

Although their repertoire drew on gospel material, they occasionally performed secular material — “Climb Every Mountain,” “What a Wonderful World” and Duke Ellington’s “Come Sunday.”

Heilbut recalled Mrs. Campbell telling him that they sang the jazz-pop standard “Come Rain or Come Shine” in a church, changing the words “I’m gonna love you” to “He’s gonna love you.”

Heilbut said that the two younger Barrett sisters have continued to perform but that Mrs. Campbell had stopped singing in the past two years after polyps had reduced her voice to a whisper. Because of arthritis, she had been in a wheelchair since the late 1990s.

Mrs. Campbell’s husband died in 2000. In addition to her sisters, she is survived by two daughters, four grandchildren and six great-grandchildren. Two other children died.

“I suppose gospel music came into being because we black people, as a race, had been crushed so much, and so cruelly,” Mrs. Campbell told the Tribune in 1990. “So these gospel songs of ours were comforting and consoling to us. I believe that the people who wrote the first gospel songs were inspired by God to write, to give our people something to feed on or to live on.”