Career spanned 50 years.

William Thomas "Keter" Betts, a giant on jazz bass who accompanied Dinah Washington, Ella Fitzgerald and helped present bossa nova to the American public, died August 6 at his home in Silver Spring, Md. He was 77.

Betts was active to the end of his 50 year career--he was to play a gig the day he died.

A native of Port Chester, N.Y., Betts switched from drums to bass as a youth. He landed his first major gig in 1949 with Earl Bostic, perhaps the most successful jazz-influenced r&b unit of the time. He left Bostic to play with the irrepressible vocalist, Dinah Washington, working with her from 1951 to 1956.

By that time, Bett's sonorous deep-groove playing had become well known, and he worked with such luminaries as Julian "Cannonball" Adderley, Woody Herman, and pianists Tommy Flanagan and Bobby Timmons.

In 1957, Betts left New York for Washington, D.C., where he teamed up with acoustic guitarist Charlie Byrd. On a trip to Brazil with Byrd, Betts and drummer Buddy Depperschmidt became intrigued with the "new samba" music of Joao Gilberto and others. Finding the new rhythms a challenge, they bought the new-sound recordings and practiced them to get the rhythm down. After, they encouraged Byrd to start playing the bossa nova tunes as well. It was a good move.

When Verve Records in 1962 asked tenor giant Stan Getz to do a bossa nova album with Byrd, the story goes that New York session players he hired had not mastered the new-samba beat. Finally, in desperation, the call went to Betts and Depperschmidt in D.C. The album, "Jazz Samba," became a best seller, even eclipsing sales of Byrd's pioneering efforts, on which Betts also played.

Betts also began an two-decade association with jazz vocalist giant Ella Fitzgerald, usually working alongside pianist Flanagan. That's him on bass on the best-selling 1960 album, "Ella In Berlin," on which she fumbled the lyrics to "Mack the Knife" and scatted her way to middle-age stardom.

In the '80s, Betts returned to Washington to stay closer to his family, becoming the eminence gris of local jazz musicians, advising and teaching as well as performing. He taught at Howard University, and taught thousands of kids the joys of music at Wolf Trap's Early Learning Through the Arts program.

Betts regularly balanced high-profile gigs at the Kennedy Center other showcase venues with "casuals" and jazz cruise appearances. In 1994, he was inducted into the Washington Area Music Assn. Hall of Fame. Last year, the D.C. chapter of NARAS awarded him its top Governor's Award for significant contributions.

Betts, who was a widower, is survived by five children, and four grandchildren.