Clark Terry, a trumpet and flugelhorn virtuoso who was an ebullient mainstay in the Duke Ellington and “Tonight Show” big bands and who became a mentor to generations of jazz players, including Miles Davis and Wynton Marsalis, has died at 94.

His wife, Gwen, announced the death Feb. 21 on the musician’s Web site. No other details were immediately available.

Mr. Terry was barely out of his teens when he came roaring out of St. Louis with a reputation for technical refinement, melodic expressiveness and hard-swinging vitality. Over the next six decades, he remained a vibrant fixture of entertainment and music education despite increasing physical frailty, including diabetes and low vision. In 2010, he won a Grammy Award for lifetime achievement.

As a band leader, studio musician and accompanist, Mr. Terry was in such constant demand that he joked of needing a suitcase just to cart around his W-2 tax forms.

In addition to his membership in the “Tonight Show” band from 1960 to 1972 — he was the orchestra’s first black member — he played with jazz powerhouses such as Count Basie, Quincy Jones, Gerry Mulligan, Ornette Coleman, Thelonious Monk, Cecil Taylor and Bob Brookmeyer.

Jazz musician Clark Terry celebrates the 20th anniversary of the Thelonious Monk Institute of Jazz during a performance in the East Room of the White House in 2006. (Kevin Lamarque/Reuters)

After serving in a Navy band during World War II, Mr. Terry advanced through some of the most popular orchestras of the era, including those of Lionel Hampton, Charlie Barnet and Basie.

Working with Basie from 1948 to 1951 was a formative period in his career. He likened it to a “prep school” in which he soaked in the band leader’s understated but compelling swing style.

Ellington had a trumpet seat free in 1951 and poached Mr. Terry from Basie.

“The first time I ever heard about Clark Terry was when Charlie Barnet told me about him,” Ellington wrote in his autobiography, “Music Is My Mistress.” “Charlie was raving: ‘Clark Terry is the greatest trumpet player in the world. You wait and see. Or better still, go get him for your band, but hurry, because soon everybody is going to be trying to get him.’ I considered myself lucky indeed to get him in 1951.”

While with the Ellington organization — one of the most inventive and acclaimed bands in the country — Mr. Terry was seeking ways to achieve a more intimate sound on his horn. Mr. Terry turned his focus to the flugelhorn, a trumpetlike instrument whose configuration permits a softer tone and had been used intermittently in jazz.

Mr. Terry’s warmly exquisite playing helped revive the flugelhorn as a respected instrument in jazz. Mr. Terry was in the Ellington band during its spirited appearance at the 1956 Newport Jazz Festival in Rhode Island and was a featured soloist in Ellington recordings such as “Such Sweet Thunder.”

Mr. Terry had long blended craftsmanship and playfulness on trumpet and, in the early 1960s, he gained recognition for a comical scat-singing style. This audience-pleasing gambit — an improvisation of grunts in the form of a lewd street-corner conversation — initially was showcased on the 1964 album “The Oscar Peterson Trio Plus One.”

With compositions such as “Mumbles” and “Incoherent Blues,” Mr. Terry was aiming for “a put-on of the old blues singers I heard as a boy in St. Louis,” he once told The Washington Post. “There always would be some lines you couldn’t make out and the singers would be making references to chicks and other people in the crowd.”

He said that during the recording session, Peterson almost fell off his piano bench with laughter. “Mumbles” became Mr. Terry’s nickname and a staple of his repertoire.

Jazz scholar Dan Morgenstern said Mr. Terry “ranks with the great trumpet players in jazz because he was such an original voice and because he was so adaptable — in big bands and small groups. He was wonderful with singers. He was an all-around musician. And he was an enthusiastic and inspiring leader. When he’d start a song, he’d tell his band, ‘One, two, you know what to do.’ ”

Clark Terry was born Dec. 14, 1920, in St. Louis, the seventh of 11 children of a laborer father.

In a city brimming with jazz sounds, Mr. Terry as a child fashioned a makeshift trumpet using household parts, including a garden hose and lead piping. The contraption made such an offensive noise that neighbors put together a collection to buy a real trumpet from a pawnshop.

His first professional engagement was with a band called Dollar Bill and His Small Change. “I missed out on part of my pay because the musicians got about 75 cents a night and X number of steins of beer,” he told The Post. “I wasn’t drinking then.”

Mr. Terry kept up a tireless freelance career even while playing with Ellington. He recorded two first-rate albums with Monk in the late 1950s, “Brilliant Corners” and “In Orbit.” He left Ellington in 1959 to join NBC as a staff musician at a time when the network was under pressure from the Urban League to hire minorities. Mr. Terry soon became a member of the “Tonight Show” band.

Mr. Terry’s broad exposure and recognition from the TV work helped launch a new career as a band leader and personality in his own right and led to his work in the 1970s as a “jazz ambassador” for State Department-sponsored tours in the Middle East, Africa and South Asia.

Mr. Terry had long been known for mentoring younger musicians and was cited as a major influence in the jazz trumpet careers of Davis, Marsalis and Roy Hargrove. Davis, who died in 1991, admired Mr. Terry’s “big, round, warm sound.” Every time Davis bought a new trumpet, he gave it to Mr. Terry for refinement.

“Man, Clark had a way of twisting and lightening the spring action of the pumps of the trumpet, just by adjusting the springs around, that would make your horn sound altogether different,” Davis wrote in his 1990 memoir. “It made your horn sound like magic, man.”

Mr. Terry, who frequently appeared at jazz clinics and music schools, said his work in jazz education had been motivated by his experiences as a young musician. He had worked with veterans who felt threatened by new talent and jealously guarded their fingering techniques, deliberately giving bad advice to “whippersnappers” seeking help.

His work as an encouraging and grueling mentor to a young pianist, Justin Kauflin, was captured in an acclaimed 2014 documentary, “Keep on Keepin’ On.”

His marriages to Sissy Terry and Pauline Reddon ended in divorce. In 1992, he married Gwendolyn Paris, who survives. A complete list of survivors could not be immediately confirmed.

Mr. Terry said that for decades his greatest regret in music was lying to Basie when he left for the Ellington band in 1951.

Ellington advised Mr. Terry to feign exhaustion and leave the band for an indefinite period. Basie accommodated Mr. Terry but subtracted an earlier $15 raise from his final paycheck.

Mr. Terry later confessed to Basie, who shrugged it off. “Why do you think I took the raise back?” Basie replied.