Jean-François Jenny-Clark, billed on many records as J.-F. Jenny-Clark or J.F. Jenny Clark, was a double bassist born on July 12, 1944, in Toulouse, France. He worked in Paris from the 1960s until his death and became one of the busiest bassists in European jazz. According to the Encyclopædia Universalis he was sixteen when the American saxophonist Jackie McLean heard him at Le Chat qui pêche in Paris and hired him for two years, 1960 and 1961. German Wikipedia adds that he taught himself the double bass for about two years before entering the Conservatoire de Paris, where he won a first prize in double bass in 1968.

In 1965 he and the drummer Aldo Romano formed the rhythm section of Don Cherry's European quintet, which recorded with Steve Lacy. Cherry's Togetherness, taped in Paris in the spring and summer of 1965 with the saxophonist Gato Barbieri and the vibraphonist Karl Berger, has him on double bass, and he is also credited on Cherry's Symphony for Improvisers (Blue Note, 1967) beside Henry Grimes. He played on Zodiac (Vogue, 1966) by Barney Wilen, and in 1969 the same circle of Paris musicians produced a run of records on which he is the bassist: Joachim Kühn's Sound of Feelings (recorded in Hamburg on January 25, 1969), Michel Portal's Our Meanings and Our Feelings (recorded June 27, 1969, with Romano, the drummer Jacques Thollot and Kühn) and Steve Lacy's Epistrophy (recorded September 23, 1969, with Romano and the pianist Michel Graillier). In 1970 he was in Martial Solal's trio for Sans tambour ni trompette (RCA Victor, recorded October 19, 1970). Around 1970 he also played concerts with Keith Jarrett.

Alongside jazz he was a member of Musique Vivante, the contemporary-music ensemble directed by Diego Masson, which played works by John Cage, Luciano Berio, Mauricio Kagel, Karlheinz Stockhausen, Pierre Boulez and Vinko Globokar. He is credited on double bass on Berio's Laborintus 2 and on Boulez's Domaines, both on Harmonia Mundi. In March 1971 he was one of four bassists, with Barre Phillips, Barry Guy and Palle Danielsson, on a session in Hamburg with the percussionist Stu Martin, issued on Japo in 1973 as Phillips's For All It Is. In 1974 he was in the pianist Jasper van't Hof's group Pork Pie with Charlie Mariano and Romano, which recorded Transitory (MPS) in Neukirchen in May 1974, and the same year he was awarded the Prix Django-Reinhardt of the Académie du Jazz.

The later 1970s and early 1980s were a period of international sideman work. He recorded Black Narcissus with Joe Henderson in Paris in October 1974 (Milestone, 1977), Enrico Rava Quartet for ECM in March 1978 with Enrico Rava, Romano and Roswell Rudd, and, in Paris on December 28, 1978, Chet Baker's Broken Wing. In 1979 he was on Paul Motian's trio record Le Voyage and Kenny Wheeler's Around 6 (both ECM), and in Paris recorded Session in Paris, Vol. 2 with the percussionist Masahiko Togashi, the trombonist Albert Mangelsdorff and the pianist Takashi Kako. He and Romano made the record Divieto di santificazione (Horo, Rome, June 1977) under both their names, he recorded New Moon (Musica, January 1978) with the American saxophonist Steve Grossman, and on July 16, 1980 he was the bassist in Mangelsdorff's trio with the drummer Ronald Shannon Jackson at Montreux. Another 1980 concert, at the Théâtre de la Ville in Paris on November 1, with Didier Lockwood, the pianist Gordon Beck, Allan Holdsworth and Romano, was released in 2020 as The Unique Concert. Michel Petrucciani's self-titled Owl record, made in Holland in April 1981, has him and Romano as the rhythm section. From 1984 to 1987 he co-led a German-French jazz ensemble with Mangelsdorff.

From 1985 he worked chiefly in a trio with the pianist Joachim Kühn and the drummer Daniel Humair. The trio's records, all with him on bass, run from Easy to Read (Owl, recorded June 1985) through From Time to Time Free (CMP, 1988), a live set at the Théâtre de la Ville in November 1989, Carambolage (CMP, 1992, with the WDR Big Band of Cologne), Usual Confusion (Label Bleu, 1993) and a set of music from Kurt Weill's Threepenny Opera, Music from Die Dreigroschenoper (Verve, 1996), to Triple Entente (EmArcy, 1998), recorded in Paris in December 1997. With Humair, Michel Portal, Martial Solal, Kühn and the guitarist Marc Ducret he played the concert released as 9-11 pm Town Hall, recorded on June 29, 1988 at the JVC Jazz Festival in New York. His only record under his name alone, Unison (CMP), was made in October 1987 with Kühn on piano and Christof Lauer on saxophone. He also made a trio record with the vibraphonist David Friedman and Humair, Ternaire (Deux Z, 1992), and two with Claudio Fasoli and Kenny Wheeler, Welcome (Soul Note, 1987) and Land (1989). Among his last recordings is Richard Galliano's French Touch (1998), on which he plays on seven tracks with Humair.

He passed away in Paris on October 6, 1998, at the age of 54, after an illness; the Encyclopædia Universalis says the end came suddenly, at the height of his powers. Records have kept appearing since: Solo, a bass solo recorded live at the Avignon bass festival on August 9, 1994, came out on La Buissonne in 2003; The Unique Concert followed in 2020; Duo - Studio 106, a piano and bass duo with Robert Kaddouch recorded for Radio France on December 3, 1995, in 2024; and the trio's On Tour 1992-1993 (Frémaux & Associés) in 2025.

His range is the first thing the records show. The same bassist is credited on the free and exploratory Paris sessions of 1965 to 1970, in the company of Joe Henderson, Chet Baker and Stan Getz with Helen Merrill, on ECM sessions led by Kenny Wheeler, Paul Motian and Enrico Rava, and on contemporary-music recordings for Berio and Boulez. AllMusic lists his styles as contemporary jazz, modern creative and post-bop, and the English Wikipedia article, citing it, calls him one of the most important bass players of European jazz. Pierre Breton's entry in the Encyclopædia Universalis praises his intonation, his legato, his intelligence and his sensitivity, and notes his taste for unusual sounds and small rhythmic cells. The trio with Kühn and Daniel Humair was the group he worked in most from 1985, and its records include Kühn's own pieces and, on the 1996 Verve record, music from Weill's Threepenny Opera.