Gary Peacock, a jazz bass player who brought a continual sense of discovery to his music during a six-decade career in which he worked alongside countless major figures, including a 30-year stint with the Standards Trio of pianist Keith Jarrett, died Sept. 4 at his home in Olivebridge, N.Y. He was 85.

The death was confirmed by drummer Jack DeJohnette, a longtime collaborator in the Standards Trio. He declined to specify a cause.

Mr. Peacock was acclaimed as one of the most dynamic and versatile bassists of his generation, but he began to play the instrument relatively late and only by default.

While serving in the U.S. Army in West Germany in 1956, he had a gig as a pianist with a combo in soldiers’ clubs when his bass player quit. The drummer suggested that Mr. Peacock take up the bass because pianists were easier to replace than bass players. With some reluctance, Mr. Peacock picked up the bass and took to it instantly.

“The instrument seemed to fall under my fingers,” he told jazz critic Martin Williams in 1963. “I never really tried to learn bass — it was as if I just started playing it.”

By 1958, Mr. Peacock was living in Los Angeles, playing with such jazz stars as guitarist Barney Kessel, vibraphonist Terry Gibbs and saxophonists Bud Shank and Art Pepper. He then heard the innovative music of saxophonist and composer Ornette Coleman, who inspired Mr. Peacock to approach his instrument with new sense of harmonic and improvisatory freedom.

He was adamant about maintaining an aesthetic of jazz purity: He played only the upright, wooden acoustic bass, never an amplified bass guitar. Yet few musicians were as adept at playing different styles of jazz.

Mr. Peacock could “range with ease between conventional structures and atonality,” musician and critic Ted Gioia wrote in “The History of Jazz,” “and was especially skillful at exploring the ambiguous middle ground between the two.”

During the early 1960s, Mr. Peacock explored the outer reaches of modern jazz with pianists Paul Bley and George Russell and saxophonists Rahsaan Roland Kirk and Albert Ayler. At the same time, he appeared in somewhat more traditional musical settings with pianist Bill Evans, trumpeter Miles Davis and drummer Tony Williams.

In a seven-month period in 1963 and 1964, Mr. Peacock performed on two landmark albums at opposite ends of the jazz spectrum: Evans’s “Trio 64,” an exercise in delicate restraint, and Ayler’s “Spiritual Unity,” a screeching, boundary-crossing free-jazz journey that practically shouted “avant-garde.”

Mr. Peacock’s “raw charisma and fiery temperament could almost match Ayler in songful intensity,” pianist Ethan Iverson wrote in Jazz Times magazine in April.

The secret to maintaining such musical flexibility, Mr. Peacock said, was to reach for the unexpected note, to search for new harmonic colors.

“To do that,” he explained to the Patriot-Ledger newspaper of Quincy, Mass., in 2017, “you have to get very quiet inside, listen, and surrender to whatever that particular musical setting is. So it doesn’t make any difference whether I’m playing standards or free stuff, because you’re giving up any kind of fixed positions or attitudes you may have about what it should or shouldn’t be.”

Beyond music, Mr. Peacock sought a wide range of experiences in life. He took LSD with 1960s anti-establishment figure Timothy Leary, moved to Japan for more than two years, became a devotee of Zen Buddhism and later returned to the United States, studying biology in college.

He never abandoned music and recording albums in Japan, largely of his own compositions. For his 1977 album, “Tales of Another,” Mr. Peacock was joined by Jarrett on piano and DeJohnette on drums. They had never worked as a trio before, but the three musicians developed a near-telepathic sense of communication.

In 1983, Jarrett brought them together again to record standards and classic jazz tunes such as “Autumn Leaves,” “On Green Dolphin Street” and “I Fall in Love Too Easily.” The results were almost electrifying in their lyrical intensity: Without apology or fanfare, Jarrett’s trio performed acoustic jazz in its most traditional form in sold-out concert halls around the world.

Following a pattern established by Evans in the 1950s and 1960s, the Standards Trio stayed together for more than 30 years, working as a unit of three equal parts, rather than as a pianist with an accompanying rhythm section. Jarrett, who was known in the 1970s for his long, improvised solo performances, brought an intimate sensitivity to his trio. Familiar tunes sparkled anew, punctuated by dynamic rhythmic accents and solos from Mr. Peacock and DeJohnette.

Jarrett’s Standards Trio performed together until 2015 and released more than 20 albums.

“Gary had a great sound, a great feel and a great imagination,” DeJohnette said. “He was really incredible to play with. His solos were full of imagination and had a lot of bounce.”

Gary George Peacock was born May 12, 1935, in Burley, Idaho. His family moved around the Northwest, where his father worked as a troubleshooter for struggling grocery stores. His mother was a homemaker.

Mr. Peacock completed high school in Yakima, Wash., and studied trumpet, piano and drums in his youth. When playing drums at his high school graduation, he said he had a revelatory experience, in which music seemed to be channeled through his body.

“It was so thorough, so complete, from the top of my head to the bottom of my toes,” he later told the Newark Star-Ledger. “On a break, I told the other players, ‘I know what the rest of my life is going to be about: music and jazz, that’s what I want to do.’ ”

After living in Japan from 1969 to 1972, he enrolled at the University of Washington, graduating in 1976 with a bachelor’s degree in biology. He stayed in Seattle for several years, teaching music at Cornish College of the Arts while performing in various groups.

Mr. Peacock’s marriages to the former Annette Coleman, better known as composer and musician Annette Peacock, and Nancy Peacock, ended in divorce. Survivors include three sons from his second marriage. A complete list of survivors could not be confirmed.

In addition to Jarrett, Mr. Peacock recorded with such jazz musicians as saxophonist Lee Konitz, guitarists Bill Frisell and Ralph Towner and pianists Marilyn Crispell and Marc Copland.

On dozens of recordings, from classic jazz to the far out, Mr. Peacock took pride in being able to fit in and, as he told the Arts Fuse website in 2017, “to be in a particular place that other people can share, enjoy, and feel something.”

One musician he refused to join onstage, however, was Elvis Costello, a New Wave rocker of the 1970s who became a genre-crossing singer-songwriter. Invited to perform with Konitz at New York’s Iridium jazz club in 2003, Costello rehearsed his songs with members of Konitz’s band, except for Mr. Peacock.

After the two spoke, according to Jazz Times, Costello gathered his music and left the club, which had to explain his absence to irate fans. Mr. Peacock, ever the jazz purist, was heard to say, “I don’t play backup for no rock star.”