Billy Preston, the splashy gospel-rooted keyboardist whose career included No. 1 solo hits and work with the Beatles and the Rolling Stones, died yesterday in Scottsdale, Ariz. He was 59.

He died after having been in a coma since November, his manager, Joyce Moore, told The Associated Press. He had voluntarily entered a drug rehabilitation clinic in Malibu, Calif., and suffered pericarditis there, leading to respiratory failure that left him in a coma.

Mr. Preston had an extensive career as a sideman, working with musicians from Little Richard to the Red Hot Chili Peppers. His own hits included the Grammy-winning instrumental "Outa-Space" in 1972 and the No. 1 pop singles "Will It Go Round in Circles" (1973) and "Nothing From Nothing" (1974). He also wrote (with Bruce Fisher) the ubiquitous "You Are So Beautiful."

But his best-known performance was the afternoon he spent on a London rooftop with the Beatles in what was their last concert, which was filmed for "Let It Be." In a 2001 interview, he recalled, "They made me feel like a member of the band."

William Everett Preston was born in Houston on Sept. 2, 1946, and grew up in Los Angeles. He was a child prodigy who accompanied the gospel singer Mahalia Jackson when he was 10. In 1958, he played the young W. C. Handy in the film biography "St. Louis Blues." Little Richard hired Mr. Preston for a European tour in 1962, and during that tour Mr. Preston met the fledgling Beatles — who were Little Richard's opening act — as well as Sam Cooke, who hired Mr. Preston for his band and signed him to his own label, SAR Records. After Mr. Cooke's death, Mr. Preston began recording instrumental albums with titles like "The Wildest Organ in Town" (1965) and "The Most Exciting Organ Ever" (1966).

He worked in the house band of the pop TV show "Shindig," then joined Ray Charles' band for three years. George Harrison of the Beatles saw him with Charles' band, and brought him to work with the Beatles.

Mr. Preston was signed to the Beatles' label, Apple, and made two albums produced by Harrison: "That's the Way God Planned It" and "Encouraging Words." He was invited to join the recording sessions that yielded "Let It Be" and "Abbey Road," where he helped hold together the band. "It was a struggle for them," Mr. Preston said in 2001. "They were kind of despondent. They had lost the joy of doing it all."

The Beatles' 1969 single of "Get Back" is credited to "The Beatles With Billy Preston," the only shared label credit in the Beatles' own career. Mr. Preston appeared at the 1971 Concert for Bangladesh that Mr. Harrison organized, and did studio work on solo projects by Mr. Harrison, John Lennon and Ringo Starr.

Mr. Preston's own career flourished in the early 1970's, when he had his major hits: synthesizer-topped instrumentals ("Outa-Space" and "Space Race") and jaunty soul songs ("Will It Go Round in Circles" and "Nothing From Nothing"). He worked in the studio with the Rolling Stones on their 1970's albums, among them "Sticky Fingers" and "Exile on Main Street," and toured with them. He was also a studio musician on Sly and the Family Stone's "There's a Riot Goin' On" and on Bob Dylan's "Blood on the Tracks."

Mr. Preston was the musical guest on the first "Saturday Night Live," broadcast in 1975. He appeared in the 1978 Beatles-inspired film "Sgt. Pepper's Lonely Hearts Club Band" as Sergeant Pepper In 1979 he had a hit duet with the singer Syreeta Wright, "With You I'm Born Again."

He continued working as a studio sideman and making solo albums through the 1980's, and he toured with Ringo Starr's All-Starr Band in 1989. But a longtime drug problem caught up with him in 1992, when he pleaded no contest to charges of assault and cocaine possession and spent nine months at a drug rehabilitation center. He made gospel albums during the 1990's, including "Minister of Music" in 1995 and "Words and Music," with Edna Tatum, in 1996. In 1997 he was sentenced to three years in prison for violating probation, and in 1998 he pleaded guilty to insurance fraud.

After Mr. Preston was released from prison, he was welcomed as a musician. He appeared in the movie "Blues Brothers 2000" and performed at the 2002 Concert for George, a tribute organized by Eric Clapton a year after Harrison's death. He appears on Mr. Clapton's album "Me and Mr. Johnson," and toured with Mr. Clapton. He was a studio musician on Neil Diamond's "12 Songs" and on the current Red Hot Chili Peppers album, "Stadium Arcadium," and he was one of the guests on Ray Charles' final album, "Genius Loves Company." He made a tribute album, "Billy Preston's Beatles Salute," in 2004, and he performed on the season finale of "American Idol" in 2005. He played his final recording session in October, for a coming album by Sam Moore of Sam and Dave.

He is survived by his sister, Gwen Gooden, and two half sisters, Lettie Preston and Rodena Williams.

"When you're doing it you're just trying to do the best you can," Mr. Preston said in 2001. "You don't know if you're doing something important, and whether it will make history has yet to be seen. Just the fact of being able to do it, and striving to do the best you can, was the accomplishment."

William E Preston