Giancarlo Schiaffini was born in Rome in 1942 and took up the trumpet in 1957, switching to trombone two years later. He is self-taught, and he reached music through science: he graduated in physics from the University of Rome in 1965, worked for Siemens on integrated circuits in 1966, and from 1967 to 1975 was a biophysicist at the CNEN nuclear studies center, publishing in immunology journals before he left research for music. In the early 1960s he was already a soloist in Italy's first free-jazz concerts, and he played in the Gruppo Romano Free Jazz with saxophonist Mario Schiano, bassist Marcello Melis and drummer Franco Pecori. In 1966 he played tuba in the musical Ciao, Rudy!, and in 1973 he made his first record as a leader, Jazz A Confronto 5 (Horo), a sextet date that included Bruno Tommaso on bass and Massimo Urbani on saxophone.

A second career ran alongside the jazz one from the start. In 1970 he studied at the Darmstadt summer courses with Karlheinz Stockhausen, Gyorgy Ligeti and Vinko Globokar, and the same year co-founded the chamber ensemble Nuove Forme Sonore with Bruno Tommaso and the Spanish composer Jesus Villa-Rojo. In 1972 he studied electronic music with Franco Evangelisti and joined the Gruppo di Improvvisazione Nuova Consonanza, the Rome collective that included Ennio Morricone and Egisto Macchi, and he stayed until 1983. He premiered Giacinto Scelsi's Tre pezzi per trombone solo in 1975, worked with John Cage during Cage's Italian tour, and from 1980 spent ten years as Luigi Nono's trombone soloist, in Prometeo (Venice, 1984) and in Guai ai gelidi mostri, and in Post-Prae-Ludium per Donau, which Nono dedicated to him. His official biography lists nine composers, among them Scelsi, Nono and Villa-Rojo, who have dedicated solo works for trombone or tuba to him.

He teaches as well as plays. From 1975 he taught trumpet and trombone at the Pesaro conservatory, and from 1980 at the Casella conservatory in L'Aquila; he has taught at the Siena Jazz summer school since 1983 and lectured at New York University in 1981 and 1982. In 2011 Auditorium Edizioni published his book on improvisation, E non chiamatelo jazz.

His free-improvising work in Italy took shape in the late 1970s. He appeared with the Globe Unity Orchestra in 1977 and 1980 and in an English-Italian improvisers' meeting in 1978 with Paul Rutherford and Evan Parker. That same year he recorded Moot (Ictus) with saxophonist Lol Coxhill and percussionist Andrea Centazzo, and two LPs (29.9.78 Pezzo and Altri Pezzi, Red Record) as one third of the SIC Trio with reedist Eugenio Colombo and percussionist Michele Iannaccone. His first solo LP, A Tung Me, followed in 1983, and in 1987 he recorded the duo album Well Actually with singer Tiziana Ghiglioni.

In 1990 he was a founding-era member of the Italian Instabile Orchestra, the collectively run large ensemble assembled for the Festival di Noci that grew to include Gianluigi Trovesi, Carlo Actis Dato, Paolo Damiani, Daniele Cavallanti, Alberto Mandarini and Pino Minafra. He is credited on its records from Live In Noci And Rive De Gier (1992) and Skies Of Europe (1995, ECM) through The Owner Of The River Bank (2003, with guest pianist Cecil Taylor) and Creative Orchestra (Bolzano) 2007 (with Anthony Braxton). His official biography records that the orchestra won the Down Beat poll for big bands in 2000. Its latest release, Plays Ellington (Felmay, 2025), is a live set recorded in Porto in December 2013 with Schiaffini as arranger and conductor, and on 30 April 2026 the orchestra reconvened at the Torino Jazz Festival to play the program live with him conducting.

Under his own name he built a run of thematic records for his own groups: About Monk (1992), a Thelonious Monk project with Trovesi and Colombo on reeds; As A Bird (1995), a Charlie Parker tribute with trumpeter Alberto Mandarini; and Dubs (1997), settings of texts by the singer Silvia Schiavoni after Joyce's Dubliners. His solo tuba and electronics record Tuba Libre came out in 2000, the year he co-founded Imprint Records with Bruno Tommaso and Alfredo Profeta, whose catalogue includes his Gershwin arrangements for Silvia Schiavoni and the brass ensemble Phantabrass. Since about 2016 his most active partnership has been with the vibraphonist and percussionist Sergio Armaroli, on the Monk and Albert Ayler "deconstruction" duos (Deconstructing Monk In Africa, 2021; Deconstructing Ayler In The Universe, 2025), the trio Trigonos (2018) with Centazzo, and the Cage-focused aboutCAGE series for Da Vinci Classics. In 2007 he was named a European Legend of Jazz at the Eurodjango/Eurojazz Awards, according to his official biography, and Casa del Jazz in Rome gave him a three-day retrospective that year.

Schiaffini's identity is split, and the split is real. His core jazz work is free jazz and free improvisation: Discogs tags 66 of the 78 releases billed under his own name as jazz (with free improvisation, free jazz and avant-garde jazz as the recurring styles), and 182 of the 218 releases carrying his credit overall. The remainder is contemporary classical music (the Luigi Nono and Giacinto Scelsi recordings, the John Cage aboutCAGE discs, his 1982 trombone-technique EP), electronic and library-music sessions, and film and stage scores. He is a Roman free-jazz pioneer who spent a decade as a new-music soloist, not a classical player who occasionally sits in with jazz groups, and the two halves feed each other: the Monk, Parker, Ellington and Ayler projects put jazz repertoire through a composer's ear, while his improvisations borrow the extended techniques and live electronics of his contemporary-music work.

His jazz reference points are named in his own record titles: Thelonious Monk (About Monk, 1992; Deconstructing Monk In Africa, 2021; Monkian Florilegio, 2026), Charlie Parker (As A Bird, 1995), Duke Ellington (the arrangements issued as Plays Ellington, 2025), Albert Ayler (Deconstructing Ayler In The Universe, 2025) and Billie Holiday repertoire (Rhapsody For Billie, 2002). Citizen Jazz's reviewer of the Monk duo noted that his trombone can play in a very jazz aesthetic even as the duo works in a language of its own. The European free-improvisation network runs through his catalogue as well: Lol Coxhill, Paul Rutherford, Evan Parker, the Globe Unity Orchestra, the AMM percussionist Eddie Prevost and pianist John Tilbury (PST (Live in Rome), 2012) and, from the rock side, Sonic Youth's Thurston Moore (Three Incredible Ideas, 2001).

He plays trombone, tuba and euphonium, and on many records adds live electronics, an approach documented from Infernal Dream (1986) to Tuba Libre (2000). The physics training is more than a footnote: he worked in laboratory research for about a decade before leaving it for music in the mid-1970s, and his live-electronics work, his multimedia pieces with Silvia Schiavoni and images by Ilaria Schiaffini (the DVD releases Ho Veduto Volare, 2009, and A Cento Metri Comincia Il Bosco, 2010) and his film scores (Marcesina, 2000) carry that technical curiosity into performance.