William Robert Dixon was born October 5, 1925, on Nantucket, Massachusetts, and moved with his family to Harlem in 1934. He came to music late by the standards of his generation: he enlisted in the Army in 1944, served with a unit stationed in Germany, and was discharged in 1946, after which he used the GI Bill to enroll at the Hartnette Conservatory of Music, where he studied from 1946 to 1951. He trained as a painter in parallel, at Boston University, the WPA Arts School, and the Art Students League, and he never treated the two disciplines as separate careers. From 1956 to 1962 he held a staff job at the United Nations, where he founded the UN Jazz Society, running concerts inside an institution that had no music program of its own.

Dixon's first records came out of a partnership with tenor saxophonist Archie Shepp. The two co-led a pianoless quartet that cut Archie Shepp - Bill Dixon Quartet for Savoy in October 1962, issued the following year, with Don Moore and Reggie Workman splitting the bass chair and Paul Cohen and Howard McRae on drums. A contractual obligation to deliver Savoy a second album, by which point Shepp and Dixon had gone their separate professional ways, produced the 1964 split LP Bill Dixon 7-tette / Archie Shepp and the New York Contemporary 5, with Dixon's septet on one side and Shepp's group, including Don Cherry and John Tchicai, on the other. Dixon also produced both dates himself, the beginning of a long habit of controlling the terms on which his music reached the public.

The event that fixed his place in the music's history was not a record. In April 1964, living on Manhattan's Upper West Side, Dixon found the Cellar Café at 251 West 91st Street and began booking Sunday concerts there. That October 1 through 4 he organized and produced the October Revolution in Jazz, four days of more than forty performances and panel discussions that drew roughly 700 people, financed largely out of his own pocket. Paul Bley, Jimmy Giuffre, Sun Ra, Rashied Ali, Giuseppi Logan, Ken McIntyre, John Tchicai, Roswell Rudd, Alan Silva, and the Albert Ayler trio appeared; Cecil Taylor, Pharoah Sanders, Ornette Coleman, Steve Lacy, and Gil Evans were among those who took part in the discussions. Within weeks Dixon co-founded the Jazz Composers Guild with Taylor, Shepp, Sun Ra, Rudd, Tchicai, and Burton Greene, a cooperative meant to give musicians bargaining power against club owners and force the press to pay attention. The Guild put on a "Pre-Halloween Jazz Party" on October 30 and 31 and the four-night "Four Days in December" series at Judson Hall, and although it collapsed within a year, the big band Carla Bley and Michael Mantler assembled under its umbrella survived as the Jazz Composer's Orchestra.

Dixon was working the other side of Greenwich Village at the same time, as a participant in the Judson Dance Theater at Judson Memorial Church. He was among the first musicians to build concerts around free improvisation and dance together, working for several years with the dancer Judith Dunn as the Judith Dunn/Bill Dixon Company. Their premiere of his piece "Pomegranate" at the 1966 Newport Jazz Festival led to a contract with RCA Victor. Signed to deliver a quartet record, he delivered instead Intents and Purposes, built around "Metamorphosis 1962-1966" for a ten-piece ensemble that mixed free players with mainstream ones: Jimmy Cheatham, Byard Lancaster, Robin Kenyatta, George Marge, Catherine Norris, Jimmy Garrison and Reggie Workman on two basses, Robert Frank Pozar, and Marc Levin, the last two his students at the time. Recorded across three sessions between October 1966 and February 1967 and released later that year, it was reviewed at five stars in DownBeat, then went out of print for decades, surfacing only on a 1972 Japanese pressing and a 1976 French one before International Phonograph finally reissued it on CD in 2011. That October he had also gone into Van Gelder's studio for Cecil Taylor's Conquistador!, alongside Jimmy Lyons, Henry Grimes, Alan Silva, and Andrew Cyrille.

In 1968 Dixon took a teaching post at Bennington College in Vermont and kept it until 1995, founding and chairing the college's Black Music Division. The move effectively removed him from the New York scene. From 1970 to 1976 he played, in his own phrase, "in total isolation from the market places of this music," recording solo trumpet at Bennington with no label waiting for the tapes. That material eventually reached the public backward: two Italian Fore LPs, Considerations 1 and Considerations 2, in 1981; a Cadence double LP, Collection, in 1985; and finally the self-released six-CD box Odyssey, issued in 2001 with two booklets of interviews, essays, and reproductions of his paintings. He continued to paint and exhibit throughout, and assembled his letters, scores, and drawings into the volume L'Opera. Twenty-five lithographs he made at URDLA in Villeurbanne in 1994 are held by the Bibliothèque nationale de France.

His recording career restarted in Italy. Giovanni Bonandrini brought a Dixon sextet to Barigozzi Studios in Milan in June 1980 and was impressed enough to ask for two albums instead of one, yielding Bill Dixon in Italy Volumes One and Two on Soul Note. A decade-and-a-half run of Soul Note records followed: the double November 1981, split between a live Zurich set and a Milan studio date and rated four stars out of four by the Penguin Guide to Jazz, which called it his small-group masterpiece; Thoughts, cut at Bennington's Paul Robeson House in May 1985 with Peter Kowald, William Parker, and Mario Pavone all on bass; Son of Sisyphus, from 1988; and the two volumes of Vade Mecum, drawn from three days at Milan's Mu Rec Studio in August 1993 with Barry Guy and Parker on basses and the British percussionist Tony Oxley, the partner who defined his late work. Dixon and Oxley recorded the two Papyrus volumes as a duo in 1998 and reconvened with bassists Matthias Bauer and Klaus Koch for Berlin Abbozzi, taped at the Podewil in Berlin in November 1999.

The last stretch of his life was his most visible in thirty years. He and Taylor, who had not recorded together in a studio since Conquistador!, cut the duo sessions later issued as Duets 1992, then met again onstage with Oxley at Victoriaville in May 2002. In June 2007 the Vision Festival gave Dixon its Lifetime Recognition and commissioned a large-ensemble premiere, taped at the Angel Orensanz Center on June 20 and released as 17 Musicians in Search of a Sound: Darfur. That September he recorded in Chicago with Rob Mazurek's Exploding Star Orchestra, and in July 2008 convened a nine-piece band at Firehouse 12 in New Haven for Tapestries for Small Orchestra, a two-CD set with a documentary film, which DownBeat gave five stars and called the strongest case for his stature since November 1981. His final performance came at Victoriaville on May 22, 2010, weeks before his death; his health had deteriorated to the point that his own solos were prerecorded and played back during the concert. The tape was issued in 2011 as Envoi. Dixon passed away in his sleep at his home in North Bennington on June 16, 2010, at 84.

Dixon built a trumpet vocabulary out of the parts of the horn most players avoid. He worked constantly in the pedal register, below the instrument's conventional floor and down into trombone and tuba territory, used half-valve positions and unvoiced breath as sound in their own right, and applied electronic delay and reverb to smear and extend what came out. He almost never used mutes, the Harmon being the one exception. What that produced was less a solo style than an orchestrator's ear applied to a single horn: a dark, pan-tonal music built around silence and long-held color, closer in its structural thinking to Webern (he titled pieces after him) than to bebop lineage. The Penguin Guide to Jazz noted that he often kept himself in the background of his own records, spreading the high voicing across his front line rather than soloing over it, and AllMusic's Brian Olewnick heard "solitary, thoughtful melancholy" with "more than a touch of Miles Davis" in the solo work. Francis Davis, writing in the Village Voice after the 2011 reissue of Intents and Purposes, called it as bold as anything released that year. Dixon's influence ran as much through organizing and teaching as through records: the October Revolution and the Jazz Composers Guild are routinely cited as the starting point of musician-run jazz presentation in the United States, a line that runs on through the Jazz and People's Movement and the AACM, and twenty-seven years at Bennington put him in front of several generations of players, among them Arthur Brooks and Stephen Haynes, who were still in his bands decades later.