Barbara Lea, an understated jazz singer whose straightforward performances made her one of the foremost interpreters of classic American songs, died Dec. 26 at a hospital in Raleigh, N.C. She was 82.

She had Alzheimer’s disease, according to a friend, Jeanie Wilson.

After an auspicious beginning in the 1950s, when she was seen as a promising young jazz star, Ms. Lea fell into obscurity for many years and turned to acting and teaching.

When she returned to the spotlight in the late 1970s, she built a quiet reputation as a peerless interpreter of the jazz and show tunes that have come to be known as the Great American Songbook. She became known for her unadorned vocal treatments, in which she revealed the emotional depth in a song’s lyrics with a minimum of ornament and fuss.

In the second half of her career, she made more than a dozen well-received recordings and was in steady demand in jazz clubs and cabarets well into her 70s. Her midrange, slightly grainy voice seemed to grow more expressive with age.

In 1987, New York Times arts critic Stephen Holden called her “one of the great jazz singers of our time.”

Unlike singers in the exuberant mold of Ella Fitzgerald and Anita O’Day, Ms. Lea did not take liberties with melody or launch into supersonic flights of improvised scat choruses, in which the singer uses nonsense syllables to simulate a musical instrument.

Instead, she followed the models of Billie Holiday, Lee Wiley and Mildred Bailey, three singers known for burrowing into a song’s lyrics to find a poignant emotional depth.

“She remains the servant of her songs,” New Yorker critic Whitney Balliett wrote in his 1988 book “American Singers.” “And she has a flawless sense of melody, of how to make a series of disconnected notes come together and move as if they were one magical note.”

With a repertoire of nearly 3,000 songs, Ms. Lea had an encyclopedic knowledge of American music. She seemed particularly attuned to the relaxed songwriting of fellow Midwesterner Hoagy Carmichael, the composer of such classics as “Stardust,” “Georgia on My Mind,” “Rockin’ Chair” and “Baltimore Oriole.”

Through the years, Ms. Lea devoted albums and nightclub performances to the works of Rodgers and Hart, the Gershwin brothers, Cole Porter, Arthur Schwartz, Cy Coleman, Jerome Kern, Johnny Mercer and female songwriters including Dorothy Fields and Carolyn Leigh.

She was, in Balliett’s words, “a singer who sings as easily as she breathes.”

Barbara Ann LeCocq was born April 10, 1929, in Detroit. When she was a child, her father, a onetime clarinetist who became an assistant attorney general in Michigan, changed the spelling of the family’s last name to Leacock.

By the time she was 7, Ms. Lea was determined to become a singer. She entered talent contests with her brother and occasionally sang with dance bands. In high school, she interviewed trumpeter Louis Armstrong and bandleader Duke Ellington for her school newspaper.

She graduated from Wellesley College in Massachusetts in 1951 with a bachelor’s degree in music theory and began singing in clubs under the name Barbara Lea. Her first album, “A Woman in Love” (1955), was named one of the finest recordings of the year.

Music magazines touted her as a rising star, and she performed with established jazz stars such as Billy Taylor, Marian McPartland, Mose Allison and Zoot Sims.

Her early success abruptly ended by 1957, when she lost her recording contract and broke up with her first husband, Robert Mantler, who was also her manager.

Two later marriages, to Stan Harris and Jim Dowd, also ended in divorce. She had no immediate survivors.

Ms. Lea began to turn to acting in the late 1950s and appeared in many off-Broadway shows and in regional theater productions across the country, ranging from Shakespeare to Sondheim. She received a master’s degree in drama from California State University at Northridge in the early 1970s and later taught acting and speech in New York.

Ms. Lea was performing at a small New York club in 1976 when songwriter Alec Wilder heard her. He asked her to perform on two episodes of his NPR radio program, “American Popular Song With Alec Wilder and Friends,” and resurrected her singing career.

In 1980, Ms. Lea published a book, “How to Sing Jazz,” in which she offered this advice: “Sing all the time. If singing is not first nature to you, sing and sing until it is second nature.”

Throughout her life, Ms. Lea was deeply interested in spiritual matters and became an ordained minister in a group called the Church of Actualism. She split her time between New York and Raleigh in recent years.

Resisting suggestions that she move toward more popular forms of music, Ms. Lea was an adamant protector of the integrity of her art form.

“It’s a great privilege to be involved with this kind of music because it has hidden depths,” she told the New York Times in 1988. “I devote most of my energy and all of my love to it.”