Guitarist Al Casey, 89, who joined Fats Waller's band in high school and provided a steady and swinging rhythmic accompaniment for the leader's vocal antics, died Sept. 11 at the Dewitt Rehabilitation & Nursing Center in New York. He had colon cancer.

Mr. Casey's association with Waller lasted from 1933 until the pianist, singer and composer's unexpected death a decade later. However overshadowed he might have been by Waller's dynamic piano style and flirtatious ad-libbing, Mr. Casey said he was hired to keep the band tight during Waller's fun yelps and scats. He appeared on more than 230 records that, all told, sold millions of copies.

The French critic Hugues Panassie, a follower of the early American jazz scene, once wrote that Mr. Casey "developed a distinctive manner of accompanying vocal choruses with chords that formed a beautiful counterpoint."

Mr. Casey stayed through many incarnations of the Waller band. His most notable recording was his bluesy and sublime solo on "Buck Jumpin' " (1941), a song that originated as a punishment for being late to a performance date. Mr. Casey came onstage while the band was playing, and Waller made him solo spontaneously to a blues number, hoping he would flail and learn his lesson.

The tune was so successful that it became Mr. Casey's unofficial anthem.

Albert Aloysius Casey was born Sept. 15, 1915, in Louisville. An orphan, his new family included uncles and aunts who were in a spiritual group called the Southern Singers. One of those uncles, featured on a radio show broadcast from Cincinnati, provided the key introduction to Waller years later.

Mr. Casey told Guitar Player magazine that he initially took violin lessons but switched to ukulele "because I wanted to be popular with the girls. It was nothing very serious, but I taught myself to entertain anybody who would listen to me."

Moving to New York City in 1930 to stay with other relatives, he began playing guitar with a school friend's band that played at Harlem's Apollo Theater and other venues. Advanced enough for his uncle to encourage a meeting with Waller, he impressed the band leader and began recording songs.

However, Waller refused to hire Mr. Casey full time until he finished high school. He later called Waller his "second father."

After some music school training, Mr. Casey developed a fast-moving style that jumped from chord to chord. This, he felt, would do justice to Waller's vocal buffoonery, as he called it.

In the late 1930s, he left Waller temporarily to work with elegant pianist Teddy Wilson and also made recordings with singer Billie Holiday and saxophonists Ben Webster, Chu Berry and Lester Young.

After Waller's death from pneumonia, Mr. Casey readily accepted work as a New York-based sideman, at that point switching to electric guitar. He led the house trio at New York's Downbeat Club, most of the time trying to imitate Nat "King" Cole's small band and even attempting singing. Apparently he was passable enough to win Esquire magazine awards for best swing guitarist in 1944 and 1945. That led to gala concerts with Duke Ellington in California and Louis Armstrong in New York.

Other jobs brought him dates with pianist Art Tatum and saxophonist Coleman Hawkins as well as bebop stars Charlie Parker and Dizzy Gillespie.

Mr. Casey struggled through the next two decades as swing fell from favor, at one point working for the New York City Health Department as a Xerox operator.

He joined a rhythm-and-blues band led by saxophonist King Curtis and also played with Frankie Lymon and the Teenagers and Curley Hamner. But he grew to dislike rock music's chord structure, dismissing it as simplistic or "distorted."

In 1981, he began a 20-year association with the Harlem Blues and Jazz Band, established by a New York orthodontist named Albert Vollmer who revered the jazz players of the 1930s. Featuring veterans of bands led by Armstrong, Ellington, Jelly Roll Morton and King Oliver, Mr. Casey liked to point out he was the group's youngest member.

Highly regarded in Europe -- he met jazz aficionados who had an encyclopedic knowledge of his recording history -- he remained largely overlooked in the United States.

"We worked with the biggest bands in the country," he told the New York Times in 1997. "We don't sound that bad. I can't understand why we don't get the recognition.''

Mr. Casey continued to enjoy experimenting with swing, which he had no doubt could "sound modern" despite the music's departure from mainstream tastes. Among his admirers were members of the eclectic band Squirrel Nut Zippers, which honored Mr. Casey with the song "Pallin' With Al."

Survivors include his wife of 67 years, Althea Jonathan Casey of New York; and a son, Al Casey Jr. of Las Vegas.

After Fats Waller's death, Al Casey, right, played with other big names, including, from left, Louis Armstrong, Roy Eldridge, Coleman Hawkins, Barney Bigard and Jack Teagarden during this jazz concert in New York in 1944.