Svend Asmussen, a Danish-born swing violin virtuoso and irrepressible showman who spent eight decades accompanying some of the world’s leading jazzmakers, including Duke Ellington, Lionel Hampton and Fats Waller, died Feb. 7. He was 100.

His son, Claus Asmussen, a composer and guitarist for Danish pop bands, confirmed the death to the Associated Press but did not provide further details. His father was performing until five years ago, when he suffered a stroke that affected his bow arm.

Mr. Asmussen’s career — to the consternation of aficionados — was perpetually overshadowed by fellow European fiddler Stéphane Grappelli. While Grappelli amassed a reputation as a jazz ambassador, globe-trotting from festival to TV appearance to nightclub, Mr. Asmussen stayed mostly in Europe, leading small groups and working with high-profile visiting entertainers.

If Grappelli was a flashy diamond, Mr. Asmussen was a hidden gem. He found a devoted following of jazz critics and discerning listeners who admired his facility as a multi-instrumentalist (vibraphone, flute and conga), sometime crooner and occasional clown in the mold of a fellow Dane, the pianist and satirist Victor Borge.

Mr. Asmussen shared stages with jazz masters including Benny Goodman and recording studios with Toots Thielemans, John Lewis of the Modern Jazz Quartet and Jean-Luc Ponty. He could play charming jazz ballads such as his theme song, “June Night,” and engage in vaudeville-esque tomfoolery, goofing with band members until songs became delightfully discombobulated.

Svend Asmussen and singer June Richmond in 1951. (Boerge Lassen/European Pressphoto Agency)

Jazz critic Will Friedwald marveled as Mr. Asmussen’s rendering of a baroque chamber work by Telemann, calling the performance “completely straight and breathtakingly moving.”

A career highlight was “Duke Ellington’s Jazz Violin Session,” an album recorded in Paris in 1963 but delayed from release until 1976, two years after the pianist-bandleader’s death.

The recording featured Mr. Asmussen dueling with two undisputed fiddle masters — Grappelli and Ray Nance (the Ellington band’s resident violinist) — on Ellington-Billy Strayhorn staples including “Take the ‘A’ Train” and “Don’t Get Around Much Anymore.”

“The result,” journalist and pop music reviewer Larry Rohter wrote in The Washington Post, “is a fascinating mixture of Continental elegance and American soulfulness.”

Rohter described the album as a summit of tasteful musicianship and submerged ego, with no violinist vying for dominance and each coloring in the songs with his distinct personality. The players, he wrote, “test and tease one another, trading choruses, playing melodies in unison, vamping and just generally frolicking their way through.”

Decades later, Mr. Asmussen told the Wall Street Journal that as the recording session ended, Ellington drummer Sam Woodyard complimented Mr. Asmussen, “You really played your ass off.”

Mr. Asmussen quipped, “I hope not — then my name would have to be ‘Mussen’ from now on.”

Svend Asmussen in 2008. (Benita Marcussen/AFP/Getty Images)

Svend Harald Christian Asmussen, whose father was a grain merchant, was born in Copenhagen on Feb. 28, 1916. He began taking piano lessons at 5, but his music teacher suggested his hands more suited the violin.

He discovered the instrument’s jazz potential at 16 after listening to recordings by the American swing fiddler Joe Venuti. Mr. Asmussen proved a quick study and, within two years, found a lucrative sideline in clubs and on record dates.

Copenhagen was a major center for touring jazz artists, especially black jazzmen, among them Louis Armstrong, who faced segregation at home. The violinist was soon working with many of the musicians.

In 1938, Mr. Asmussen’s quartet opened in the Danish city of Aarhus for the brilliant, hard-living stride pianist and composer Waller.

“During our set,” Mr. Asmussen later told the Wall Street Journal, “Fats stood in the wings and listened, with a bottle of milk in one hand and a bottle of scotch in the other. By the time we finished, both bottles were empty.”

He added that Waller subsequently asked to sit in with Mr. Asmussen’s band at a nearby dance hall. The violinist was flattered but also unnerved because the bandstand dangled over the dance floor, and Waller weighed more than 250 pounds. But the bandstand held, he recalled, even as Waller turned in a vigorous performance. “He played louder than all of us put together!” Mr. Asmussen said.

Mr. Asmussen built a solid reputation through his appearances in European nightclubs and on film. The outbreak of World War II in 1939 and the Nazi occupation of Denmark curtailed his appearances beyond Scandinavia. In 1943, he was arrested by the Gestapo and imprisoned in Berlin as part of a general roundup of hundreds of prominent Danes.

Quickly picking up his career after his release, he returned to jazz but also embraced novelty numbers. In one routine, his interpretation of Beethoven’s “Minuet (in G)” goes incongruously awry, diverting into Verdi, Cole Porter and “It’s a Long Way to Tipperary.” In the mid-1950s, he led a group under the name Svend Asmussen and His Unmelancholy Danes.

Mr. Asmussen also paired in the late 1950s and early 1960s with Danish guitarist Ulrik Neumann and Swedish soprano Alice Babs to form the Swe-Danes, an act that involved the trio scatting or using their voices to mimic an entire orchestra of sound. They toured internationally and made several records before disbanding.

Mr. Asmussen surfaced again as a dazzling straight jazz musician on “Two of a Kind” (1965) opposite Grappelli and on “The Violin Summit” (1966) featuring Stuff Smith, Grappelli and Ponty.

His first wife, Annegrethe Thomassen, with whom he had three children, died in 2000. In 2005, he married Ellen Bick Meier. Survivors include his wife and children.

Well into his senior years, Mr. Asmussen continued making records, including “Svingin’ with Svend” (1987) with American mandolinist David Grisman and “Still Fiddling” (2002), opposite Danish guitarist Jacob Fischer, a frequent musical partner. A few years ago, he was the subject of a documentary, “Svend Asmussen — The Extraordinary Life and Music of a Jazz Legend.”

More than anything, Mr. Asmussen said he thought of himself as an entertainer. “I played revues for 20 years,” he told the online publication allaboutjazz. “A typical audience consists of 10 percent jazz fans; I have to reach the remainder as well.”