Keter Betts, 77, a jazz bassist heard on more than 200 recordings, notably with guitarist Charlie Byrd and singers Dinah Washington and Ella Fitzgerald, was found dead Aug. 6 at his home in Silver Spring.

The cause of death has not been determined, according to the McGuire funeral home in the District.

Trumpeter Clark Terry, formerly with the Duke Ellington and "Tonight Show" orchestras, said Mr. Betts was "on the top plateau of all the bass players."

Mr. Betts played in bands with Oscar Peterson, Tommy Flanagan, Woody Herman, Nat Adderley, Joe Pass, Clifford Brown and Vince Guaraldi.

After he made the Washington area his home in the mid-1950s, Mr. Betts teamed with Byrd, the lyrical guitarist who made his name with sensual, samba-inspired bossa nova music. They were regulars at the Showboat Lounge in the District and made several State Department-sponsored trips abroad.

During one trip to Brazil, Mr. Betts became enthralled with samba records and, he said, spent months persuading Byrd to play the music around Washington.

Although Mr. Betts was on the million-selling "Jazz Samba" (1962) album -- recorded at Washington's All Souls Unitarian Church -- stars Byrd and saxophonist Stan Getz were credited with launching the bossa nova craze in the United States.

One of the most memorable songs from the album, "Desafinado," featured Mr. Betts doing the supple bass-line introduction. But his contribution to finding the music went unheralded until recent years, after he spoke to JazzTimes magazine about his role.

Ken Kimery, a producer and drummer with the Smithsonian Jazz Masterworks Orchestra, told The Washington Post in 2003: "My experience with him is that he feels the story will come out, and he does not feel he'll have to be the one who takes the effort to do that. . . . Here's a gentleman who's done so much and does not feel the need to self-promote."

William Thomas Betts was born in Port Chester, N.Y., July 22, 1928, and was raised by his single mother, a domestic worker. He got his nickname when a family friend said the baby was as cute as a mosquito. Mosquito became Skeeter, then Keter.

One day, his mother sent the youngster for milk and bread at the market. Thrilled by the sound of a passing Italian parade, he followed the drummer across town. He was gone four hours with the milk and bread.

"My mother almost killed me when I got home," he told an interviewer. "I got a whippin'. After that, I told my mother I wanted to play drums."

She figured that if her fury did not dissuade him, he must be serious. She arranged for drum lessons.

His switch to the bass came one day in 1946, his senior year in high school. He went to New York to see Cab Calloway's big band and meet the drummer. When bassist Milt Hinton appeared at the stage door, he told the teenager that the drummer was gone but that he would spring for a 35-cent lunch. He also talked up the bass.

Ultimately, Hinton's words were not as persuasive to Mr. Betts as the fact that carrying a drum set up four flights of stairs to his mother's apartment was excruciating.

Almost from the start, Mr. Betts's professional career brought him to Washington. New York area saxophonist Carmen Leggio invited Mr. Betts to play with his band at a club near the Howard Theatre in 1947.

In 1949, while Mr. Betts was playing at Washington's Club Bali, R&B bandleader Earl Bostic heard and hired him. He made his recording debut that year on Bostic's rendition of "Wrap Your Troubles in Dreams."

"I didn't want to play R&B," Mr. Betts said. "But it was a good chance to go on the road and see the country."

He met Dinah Washington in 1951, when she and pianist Wynton Kelly were doing a one-nighter with Bostic's band. The singer offered Mr. Betts a job, and he spent five years with the notorious Queen of the Blues and cut several classic records, including "Dinah Jams" (1954) and "Dinah!" (1956).

Her gruff exterior was "for the people," Mr. Betts said. "She was a different person inside." She paid for Mr. Betts's wedding reception in 1953 at Birdland in New York; Tito Puente provided the music.

Washington taught Mr. Betts a secret to good musicianship: Learn the lyrics. She said the best musicians know the entire song, not just the chord changes.

"There's an art to playing behind the singer," he said later. "When the singer comes onstage, they're buck naked. And it's the job of the group backing her up to dress that person for the audience."

He met Fitzgerald through his golfing partner, bassist Ray Brown, the singer's ex-husband and business manager. Mr. Betts played with Fitzgerald in the mid-1960s and again from 1971 to 1993, often doing weeks of one-nighters around the world.

Meanwhile, he played at the Kennedy Center and on jazz cruises. He also stayed active in musical education through Head Start, among other programs. At the Wolf Trap Institute for Early Learning Through the Arts, he often amazed the kindergarten set by taking "Happy Birthday" and covering it in different styles: classical, Brazilian, country and western, rock and jazz.

In 1994, he was inducted into the Washington Area Music Association's Hall of Fame.

He emerged as a bandleader with a flurry of recent CDs and composed a handful of songs, notably the sweet and tender "Pinky's Waltz," in memory of his wife, Mildred Grady Betts, who died in 2000.

Survivors include five children, William Betts Jr. of Washington, Jon Betts of Olney, Derek Betts of Los Angeles and Jacquelyn Betts and Jennifer Betts, both of Silver Spring; and four grandchildren.

Keter Betts was "on the top plateau of all the bass players," a fellow musician said.