Sleepy LaBeef, a rockabilly and country singer who began his career in the mid-1950s and was known as a “human jukebox” for his seemingly limitless repertoire of songs, died Dec. 26 at his home in Siloam Springs, Ark. He was 84.

His wife, Linda LaBeff, announced the death on Facebook but did not cite a cause; LaBeff was the singer’s real surname. He had heart bypass surgery in 2003 but continued to perform until shortly before his death.

An imposing man who stood 6-feet-6 and weighed more than 250 pounds, Mr. LaBeef sang in a deep, drawling baritone. His record sales were never huge, but his live performances helped energize a resurgence of rockabilly music in the 1970s and ’80s.

Mr. LaBeef began his career as a gospel singer but changed course when he heard Elvis Presley’s recordings on Sun Records in 1954.

“I said, ‘Hey, this is crazy. This is what I’m singing,’ ” he told the Boston Globe in 1983. “Except that he was singing blues lyrics and country lyrics with the same gospel beat I was using.”

He knew thousands of songs from the rock-and-roll, gospel, blues, country and pop songbooks, which he drew on for marathon medleys. A waltz might suddenly give way to a shuffle and then just as suddenly to a rocker. It all depended on how he read the audience’s mood. The crowds loved it, but for his backup band it was daunting.

On Facebook, rockabilly guitarist Deke Dickerson recalled that one nightclub turned the electricity off when Mr. LaBeef continued playing after last call. Dickerson wrote that Mr. LaBeef’s shows “would consist of him performing for 3 or 4 hours straight, no breaks, with short- and long-term band members holding on for dear life, often not knowing the songs as Sleepy plowed through them like a mule plowing through hard and rocky Arkansas farmland.”

“It’s about having fun,” Mr. LaBeef once said, “not necessarily about teaching my backing band a lesson. They’ll learn as they go, on-the-job training.”

On New Year’s Day 1977, his van caught fire en route to a show in Amesbury, Mass. Although his clothes were destroyed, he made it to his gig at Alan’s Fifth Wheel, a truck stop honky-tonk. The owners offered him a residency.

Critic Peter Guralnick, who lived nearby, heard Mr. LaBeef many times at the truck stop, where he appeared for several years. In his book “Lost Highway,” Guralnick wrote that Mr. LaBeef “is possessed not only of an encyclopedic knowledge of the field but of the flair, originality, and conviction to put the music across as well. At this point, I can’t count the number of times I’ve seen him perform, but I’ve never seen Sleepy do a set that was less than entertaining, nor have I known him to play the same set twice.”

Thomas Paulsley LaBeff was born July 20, 1935, in Smackover, Ark., the youngest of 10 children in a farming family. He reportedly got the nickname Sleepy because of a lazy eye.

After trading a rifle for his first guitar, he began playing in church. His early influences included religious singers Sister Rosetta Tharpe, ’Cile Turner and Brother Claude Ely. In addition to guitar, he played fiddle, piano and upright bass.

He worked as a land surveyor in Houston, beginning in his late teens, and sang in gospel groups before making his first recordings in 1957. He adopted the stage name LaBeef in 1965.

His marriages to Louise Barstow and Oquita Richards ended in divorce. Survivors include his wife of 41 years, the former Linda Cerny of Siloam Springs; five children; and 12 grandchildren.

Mr. LaBeef starred in a low-budget exploitation movie, “The Exotic Ones” (1968), also called “The Monster and the Stripper.” Undoubtedly cast for his size and girth, he portrayed a swamp monster captured by hunters and exhibited in a strip club. “Sleepy LaBeef Rides Again,” a documentary film about his career, was released in 2013.

His early records from the late 1950s, mostly for small labels and usually credited to Sleepy (or Tommy) LaBeff, are prized by collectors for their raw spontaneity and their rarity — an unfortunate reflection that they didn’t sell.

Although the song “Blackland Farmer” briefly entered the country charts in 1971, Mr. LaBeef never had a big hit. Throughout the 1970s and ’80s, he recorded for Rounder Records and the reactivated Sun label, but he felt something was often missing from the albums.

“When you go into a studio, you hope many people are going to hear your record, but you’re still singing to an engineer and microphones,” he told the New York Times in 1991.

“But really, it’s hard for me,” he said. “It’s much more thrilling to get onstage and perform to people and see them get into what you’re doing.”