Bo Diddley, 79, the blues singer and guitarist whose propulsive beat and swaggering stage presence helped set the foundation for rock-and-roll, died yesterday at his home in Archer, Fla. He retired from active performing after a stroke in May 2007.

Diddley, a dazzling rhythm guitar player, was one of the most influential musicians of the 1950s and 1960s and crossed barriers between blues and rock in a way few others managed, before or since. He influenced generations of rock musicians, including the Rolling Stones, and won many of his profession's highest honors. Some of Diddley's songs, such as "Who Do You Love" and "I'm a Man," have become rock and blues standards.

A virtuoso showman, Diddley displayed a fondness for horn-rimmed glasses, dark Stetson hats and suggestive gyrations that often incorporated his distinctive, box-shaped guitars. Critics singled out his charisma, with a Washington Post reviewer in 1961 writing that Diddley's hindquarters shake "makes Elvis Presley seem even a great oaf, to put it baldly."

In a five-decade career, Diddley recorded blues shuffles and doo-wop ballads, but it is the syncopated style established on his first record, "Bo Diddley" (1955), for which he will be most remembered.

The title song, which Diddley performed to a national television audience on Ed Sullivan's variety show, established the Bo Diddley beat. The song could barely be described as melodic. Its one chord was played in an insistent syncopated rhythm -- Bomp-a-bomp-a-bomp. Bomp-bomp -- and its nursery rhyme-like lyrics established his persona.

Bo Diddley buy baby a diamond ring,
If that diamond ring don't shine,
He gonna take it to a private eye,
If that private eye can't see,
He'd better not take the ring from me.

Musicologists believe the Bo Diddley "beat," or signature rhythmic pattern, sometimes expressed in such words and syllables as "shave-and-a-haircut two bits," originated with Afro-Cuban clave rhythms. Diddley said he first heard the beat in church.

Diddley had multiple hits on Billboard's rhythm-and-blues charts, but only one song, "Say Man" (1959), was on the magazine's Top 40 pop charts.

The latter record, essentially a comedy routine, harkened back to the schoolyard practice of "signifying," or one-upping one another with insults. It featured Diddley and his maraca player, Jerome Green, trading put-downs to their own instrumental accompaniment.

Some critics have cited the record as a precursor to rap and hip-hop.

A self-taught guitarist, Diddley developed dynamic fingering techniques that allowed him to do more with less. For example, he tuned his guitar to a D major chord and could fret many chords with his just index finger.

In Diddley's music, the guitar functioned with the drums and maracas almost as a percussion instrument, unusual because blues music often had the guitarist playing solos. Using the tremolo effect of his amplifier, Diddley's notes were broken into staccato fragments that enhanced the percussive effect.

Adding to his stage flamboyance was his electric guitar, often a red rectangular model custom-built for him from his own design by the Gretsch musical instrument company. His guitars were prominently displayed on his record covers for years and became part of his image.

Rock musicians have borrowed the Bo Diddley beat for their own songs, including Buddy Holly's "Not Fade Away" in the 1950s, the Who's "Magic Bus" in the 1960s, and the Smiths' "How Soon Is Now" in the 1980s. "Not Fade Away" was later covered by the Rolling Stones.

Despite his stature, Diddley was bitter about how music company executives had allegedly cheated him of royalties during his prime. He said he had signed away the rights to many of his songs at a vulnerable time, in the late 1950s, when he needed money to cover debts, including his children's education.

"You can get ripped off easier by a dude with a pen than you can by a dude with a gun," he told the New York Times in 2003.

His fight for royalties was his consuming crusade until his death, but he got little for his trouble other than press attention.

Robert Palmer, a popular-music scholar, wrote: "You can't copyright a rhythm, a beat, a guitar sound or a riff pattern. American copyright law follows the European tradition that a song is words, melody and chords, everything else is secondary. But it just so happens that this -- everything else -- is the area in which Bo Diddley made many of his contributions to American popular music."

Otha Ellas Bates was born Dec. 30, 1928, on a farm near McComb, Miss. He and his unwed teenage mother went to live with a cousin, Gussie McDaniel, who he said "raised us both." She gave the child her surname and took him with her to Chicago in the mid-1930s.

Ellas McDaniel, as he became known, took violin lessons at Ebenezer Baptist Church on Chicago's South Side and showed great promise. But his musical tastes veered to the uninhibited sound of Pentecostal music and the blues guitar of John Lee Hooker. Diddley credited Hooker's 1949 R&B hit "Boogie Chillen" with moving him to guitar. And, he said: "I looked around and didn't see too many black violinists."

Tensions erupted in the family over the young musician's interest in "the devil's music." He left home, quit vocational school at 15 and boxed for a time under the name Bo Diddley, a name he said he chose became it sounded like a fighter's moniker. He said he had learned how to punch as a child after being taunted by Chicago schoolyard bullies for his "country ways."

As a guitarist, he played on South Side street corners for nickels and moved into bars such as the 708 Club with Billy Boy Arnold on harmonica and Jody Williams on lead guitar.

In 1955, he signed a record deal with Checker, a Chess Records subsidiary, which led to his debut single that featured "Bo Diddley," with "I'm a Man" on the flip side. The record spent two weeks at No. 1 on the R&B charts and landed him on Sullivan's TV show. Sullivan had asked Diddley to play the Tennessee Ernie Ford hit "Sixteen Tons," but Diddley, who later claimed he forgot the lyrics, instead played "Bo Diddley." He was never invited back.

Diddley made several hit R&B records, including "Diddley Daddy," "Pretty Thing," "I'm Sorry," "Road Runner," "Mona" and "Crackin' Up." He also toured with Chuck Berry, with whom he later jammed on the 1964 release "Two Great Guitars."

Diddley's last single to reach the charts was "Ooh Baby" in 1967, but he continued an active career as a live attraction at festivals and was featured in concert films such as "The Big T.N.T. Show" (1966) and "Let the Good Times Roll" (1973).

Starting in the late 1950s, he lived in Washington for several years and was an active presence at the Howard Theatre. He also recorded albums in his basement studio, including "Bo Diddley Is a Gunslinger," and helped the career of local soul singer Billy Stewart. He played guitar on a recording by the Marquees, a Washington vocal group that included a young Marvin Gaye.

The mid-1960s proved leaner economically than Diddley liked, in part because of changing music tastes triggered by the British invasion of the Beatles and the Rolling Stones as well as the rise of soul music.

He found work as a deputy sheriff in Los Lunas, N.M., in the early 1970s, and in recordings of that period, he sometimes changed his musical style to fit the public appetite for psychedelia and funk. But it was his early breakthrough sound that captivated audiences and renewed interest in his career.

In 1979, he went on a high-profile tour with the British punk band the Clash and played at the Philadelphia "Live Aid" benefit concert in 1985, an event broadcast to millions of people around the world.

He said the need for income spurred his prolific touring schedule into recent years. In 1989, he appeared in Nike advertisements titled "Bo Knows" with football and baseball star Bo Jackson.

With Jackson attempting a guitar line, Diddley faced the camera and said, "He don't know Diddley," a line that became a national catchphrase. Diddley also performed at the presidential inaugurations of George H.W. Bush and Bill Clinton.

Diddley was inducted into the Rock and Roll Hall of Fame in 1987 and received a 1998 Grammy Award for lifetime achievement.

His marriages to Louise Woolingham, Ethel Smith, Kay Reynolds and Sylvia Paiz ended in divorce. He had spent several years settled in Washington with Reynolds in the early 1960s and spoke of threats he received for living with her, a white woman many years his junior.

Survivors include two children from his first marriage; two daughters from the third marriage; a brother; 15 grandchildren, 15 great-grandchildren; and three great-great-grandchildren.

Diddley said he largely shunned the vices -- liquor, drugs -- that prematurely ended the careers and lives of many peers. He described a great need to remain disciplined in a difficult profession.

"When I first became famous, it really freaked me out," he told the Orlando Sentinel in 1985. "You see, I'm a very different person onstage, very different. I have a job to do, and I ain't got time to be throwing the bull. . . .

"I decided right from the beginning of my career I'd give it all I got, put on the most outrageous show I could," he said. "I'm two people really. Up there I'm Bo Diddley. At home I'm Ellas McDaniel, the same plain, straight dude all the time."