Didier Levallet was born on July 19, 1944, in Arcy-sur-Cure, in the Yonne department of Burgundy, France. He taught himself the alto saxophone as a teenager, then studied double bass at the conservatoire in Lille while attending the École supérieure de journalisme there. He moved to Paris in 1969 and began working as a professional bassist. His French Wikipedia entry names Georges Arvanitas, the pianist Siegfried Kessler, the trumpeter Ted Curson, Mal Waldron, Johnny Griffin, Kenny Clarke, Slide Hampton, the pianist Freddie Redd and Hank Mobley among the musicians he played with in those first Paris years. A record from July 1971, Redd's trio album Under Paris Skies, has him on bass.

In 1970 he founded the quartet Perception with the saxophonist Yochk'o Seffer (billed on some records as Jeff Seffer), Kessler and the drummer Jean-My Truong. The group toured abroad and made a run of records: Perception (1971), Perception & Friends (1973) and Mestari (1974), a live set recorded in Paris on November 28, 1973 that won the Prix Boris Vian of the Académie du Jazz in 1974. In 1972 he set up ADMI, the Association pour le développement de la musique improvisée, which put on concerts and issued records; Perception & Friends came out on the A.D.M.I. label. In 1975 he recorded a duo LP of spontaneous compositions for double bass and percussion with Yves Herwan-Chotard, and he was the bassist on a series of albums by the poet-singer Jacques Bertin, among them the live Enregistrement public 29. IX.78. After a 1974 trip to the United States with the saxophonist Byard Lancaster he formed Confluence, a changing ensemble of strings and percussion that recorded Arkham (1977) and Chroniques terrestres (1978) for RCA Victor and stayed together until 1980. On December 8, 1976 he was the bassist in the American saxophonist Frank Lowe's quartet at a concert in Rouen, issued as Tricks of the Trade. In 1977 he also started the jazz meetings at Cluny in Burgundy, a festival that has run in one form or another ever since.

From 1978 he led Swing Strings System, a string orchestra with drums for which he wrote and arranged. Its first record, Swing Strings System, was made in Paris in October 1978 with Christian Escoudé on guitar, Bernard Lubat on drums and the violinist Didier Lockwood, and the Prix Boris Vian went to it in 1979. The group was renamed Super Strings System in 1989. In 1981 he formed a trio with the violinist Dominique Pifarély and the guitarist Gérard Marais, recorded live as Instants chavirés (Open, 1981) and followed by Eowyn (Label Bleu, 1986). He also led a quintet, an octet and a tentet; the octet record Scoop (1983) has Steve Lacy, Tony Oxley and Tony Coe in it. In June 1981 he was on bass in Chris McGregor's Brotherhood of Breath at Angoulême, recorded as Yes Please. He taught jazz at the conservatoire in Angoulême from 1981 to 1992 and at Montreuil from 1992 to 2000, and later taught at the University of Poitiers. With the sociologist Denis-Constant Martin he wrote L'Amérique de Mingus (P.O.L., 1990). He kept a free-improvisation side alongside the writing, on Cordes sur ciel (1990) with the German drummer Günter Sommer and the saxophonist Sylvain Kassap, and on Outlaws in Jazz (1994) with the saxophonist Daunik Lazro, the trumpeter Jac Berrocal and the drummer Denis Charles.

From 1997 to 2000 he was the musical director of the Orchestre national de jazz, the state-funded French jazz orchestra, which recorded ONJ Express (1998), Sequences (1999) and Deep Feelings (2000, with the singer Jeanne Lee) under his direction. He was made a Chevalier des Arts et des Lettres in 1984 and a Chevalier de l'Ordre national du Mérite in 1998. From 2001 to 2010 he ran L'Allan, the national performing-arts venue (scène nationale) in Montbéliard.

Since 2008 he has been artistic director of Jazz Campus en Clunisois, the festival that replaced the Cluny meetings he started in 1977. Jazz Magazine, reviewing the 49th edition in August 2026, described him as the festival's founder, still programming it and introducing the groups on stage, and said he was preparing its 50th anniversary for 2027. His later records include Songes, silences (Sans Bruit, 2011), recorded in Montbéliard in 2006, and Voix croisées (Frémeaux & Associés, 2013) with his quintet. He is also among the many players on 13 Miniatures for Albert Ayler (RogueArt, 2012), a tribute concert recorded at the Fondation Cartier in Paris on December 2, 2010. The ONJ Youth Orchestra devoted its 2024-2025 season to his compositions, conducted by Sophia Domancich.

Levallet came up in the free-jazz and free-improvisation scene of early-1970s Paris. Discogs files the Perception records under free jazz, and his later records with Günter Sommer, Sylvain Kassap and Daunik Lazro under free jazz and free improvisation. He did not stay in one place: with Swing Strings System and Super Strings System he wrote for cellos, violins, guitar and drums, and for the Orchestre national de jazz he is credited as composer, arranger and director on ONJ Express and as composer and arranger on Sequences. Tributes recur in his work: Quiet Days... (1985) includes a piece titled "For Harry Miller", Generations (1992) opens with "Chris McG", he plays on the Albert Ayler tribute concert record, and he plays bass on Yochk'o Seffer's Ornette for Ever, a record of compositions by Ornette Coleman. He also co-wrote a book on Charles Mingus.

A thread through his records is work with British improvisers: the trumpeter Harry Beckett and the drummer Tony Marsh on Images of Clarity (1993), the saxophonist Chris Biscoe on his quintet and ONJ records, and Tony Oxley, Tony Coe and Mark Charig on Scoop. Jazz Magazine's 2026 festival report calls him generous in sharing and passing on what he knows and a rare expert on jazz history who is open to current trends.