Willie James Ulmer was born February 8, 1940, in St. Matthews, South Carolina, the eldest of eight children of a Baptist preacher who handed him his first guitar at four. By seven he was singing baritone and playing in his father's gospel quartet, the Southern Sons, and he stayed with the group until he was thirteen. His mother disapproved of secular blues, which did nothing to stop him from absorbing it. He left the South in 1959 for Pittsburgh, where he backed pop and doo-wop acts including the Del-Vikings, worked the organ-trio circuit, and picked up the nickname that followed him for the rest of his life: locals called him "Youngblood," which got shortened to "Blood."

In 1963 he moved to Columbus, Ohio, and formed Blood and the Bloodbrothers, a working band with a steady room at the 502 Club backing touring singers. He found the commercial repertoire confining and got more out of playing with organist Hank Marr, whose quartet he toured Europe with and recorded alongside on Sounds from the Marr-Ket Place (King, 1968). A 1967 move to Detroit changed his playing permanently. He taught guitar at the Metropolitan Art Complex, studied reading and composition, ran a free-jazz group called Focus Novii with drummer Doug Hammond, and worked out the tuning that became his signature: he abandoned standard tuning and set his strings in unison, which stripped the guitar of the piano-derived chord voicings he had come to distrust and left him with a clanging, open, unresolved sound that nobody else was making.

Ulmer arrived in New York in 1971. Playing his own material at Minton's Playhouse in Harlem, where he had been hired to play blues, he met Rashied Ali, and it was Ali who introduced him to Ornette Coleman. The introduction reorganized his career. Ulmer moved into Coleman's loft and studied harmolodics, Coleman's theory that harmony, movement and melody carry equal weight and that every instrument in an ensemble is simultaneously a melodic and a rhythmic voice. It matched the atonal experiments Ulmer had already been running in Detroit, and he spent the rest of his life saying so: he told interviewers he followed harmolodic theory and still followed it, and that to follow it properly he had to become a harmolodic person rather than merely play harmolodic music. He performed with Coleman through the mid-1970s, including dates at the Ann Arbor Blues and Jazz Festival in 1974 and the Five Spot in 1975, but the partnership was never documented on a Coleman leader album. Its studio record runs the other direction, on Ulmer's own.

The sideman work of those years put him in unusual rooms. In 1973 he became the first guitarist Art Blakey ever hired for the Jazz Messengers, briefly; he played on organist Larry Young's Lawrence of Newark (Perception, 1973) and on Joe Henderson's Multiple (Milestone, recorded January 1973), and later on Arthur Blythe's Lenox Avenue Breakdown (Columbia, 1979) and Illusions (1980). He also cut a two-track LP with Rashied Ali for Ali's own Survival Records: the Rashied Ali Quintet album (SR-102, 1973), recorded at Marzette Watts's studio with John Dana on bass, Bob Ralston on tenor and Earl Cross on trumpet. Its B side is a piece credited to Ulmer called "Theme for Captain Black," six years before he made it the title track of his debut.

That debut, Tales of Captain Black, was recorded December 5, 1978, at R.P.M. Sound Studios and released on Artists House in 1979 with Ornette Coleman on alto saxophone, Coleman's son Denardo on drums, and Jamaaladeen Tacuma on electric bass. Are You Glad to Be in America?, cut in a single day on January 17, 1980, added David Murray, Oliver Lake and Olu Dara to a rhythm section of Amin Ali and Grant Calvin Weston, put Ulmer's flat, conversational singing at the front, and came out on Rough Trade in Britain, an unusual home for a jazz guitarist and a sign of where his audience actually was. Columbia signed him in 1981 and got three albums: Free Lancing (1981), Black Rock (1982), and Odyssey (1983), the last of them a trio with violinist Charles Burnham and drummer Warren Benbow that finished twentieth in the Village Voice Pazz and Jop critics' poll for 1983 and is the record most often named as his best. It was also his last for a major label.

Dropped by Columbia, Ulmer built the rest of his career out of ensembles and independent labels. The Music Revelation Ensemble, which had made No Wave for Moers Music in 1980 with David Murray, Amin Ali and Ronald Shannon Jackson, became a standing project on the Japanese label DIW from 1988, its horn section rotating through Murray, Jamaaladeen Tacuma, Arthur Blythe, Hamiet Bluiett, Sam Rivers, Pharoah Sanders and John Zorn across seven albums. Phalanx, the quartet he co-led with saxophonist George Adams, ran from 1985 to 1988 and put Rashied Ali and bassist Sirone in the rhythm section for its two DIW records. Odyssey the Band reconvened the Odyssey trio for Reunion (Knitting Factory, 1998) and Back in Time (Pi, 2005). The James Blood Ulmer Blues Experience made Blues Allnight (1990) and Live at the Bayerischer Hof (1994) for German labels, and Third Rail, with Bill Laswell, Bernie Worrell, Amina Claudine Myers and Joseph "Zigaboo" Modeliste, made South Delta Space Age in 1995.

The last act was the blues, played straight. Guitarist Vernon Reid produced four albums that turned Ulmer back toward the material he had grown up around: Memphis Blood: The Sun Sessions, cut over three days in April 2001 at Sun Studio in Memphis and nominated for the 2002 Grammy for Best Traditional Blues Album; No Escape from the Blues: The Electric Lady Sessions (2003); Birthright (2005), a solo record of voice, guitar and flute; and Bad Blood in the City: The Piety Street Sessions (2007), eleven songs recorded in New Orleans about the aftermath of Hurricane Katrina. In 2009 he started his own label, American Revelation, and used it to issue live tapes from his own archive, including the 1986 Bremen concert that finally documented the first Phalanx lineup. He played his last concert at the Detroit Jazz Festival on September 1, 2024, and died peacefully in New York on June 3, 2026, at eighty-six, survived by six children, twelve grandchildren and thirteen great-grandchildren.

Ulmer's sound came from a decision most guitarists never make: he retuned the instrument in unison and stopped voicing chords the way a pianist would, which left him playing lines and clusters that ring against each other without resolving. Onto that he grafted Ornette Coleman's harmolodics, and the result was a rhythm-and-lead instrument at once, capable of stating a theme, comping and soloing in the same phrase. Critic Greg Tate placed him "between Jimi Hendrix and Wes Montgomery on one hand, and P-Funk and Mississippi Fred McDowell on the other," which is a fair map of the four traditions he was working: rock volume and distortion, jazz harmony, funk time, and Delta blues form. Newsweek called him the most original guitarist since Hendrix and Montgomery in 1981, and the phrase followed him through four decades of reviews. He sang in a flat, unhurried Southern voice that critics found either the weakest or the most affecting thing about his records, and he never entirely reconciled his two constituencies: by the mid-1990s he was saying openly that he wanted to stop mixing his styles and perfect them separately, which is roughly what the Vernon Reid blues albums and the DIW avant-garde records did. His influence ran mainly through the downtown New York and free-funk generations rather than through mainstream jazz guitar, and it is audible in Reid's own playing with Living Colour and across the Knitting Factory scene.