William Walter "Billy" Hart was born November 29, 1940, in Washington, D.C., into a family already close to music: his paternal grandmother was a pianist who accompanied Marian Anderson, and his maternal grandmother bought him his first drum kit. He grew up near the Spotlite Club and heard Lee Morgan, Ahmad Jamal, and Miles Davis there as a teenager. At seventeen he joined the band of Washington tenor saxophonist Buck Hill alongside schoolmates Reuben Brown and Butch Warren; Buck Hill also handed him his first Charlie Parker records. Hart enrolled at Howard University to study mechanical engineering and left before finishing, taking road work with Otis Redding and Sam and Dave and then a job with singer and pianist Shirley Horn, whom he has repeatedly credited with speeding up his musical development more than any other early employer.

The 1960s turned him into a touring professional. He worked with the Montgomery Brothers in 1961, joined organist Jimmy Smith from 1964 to 1966 (his recorded credits with Smith include Christmas Cookin' and the soundtrack La métamorphose des cloportes), and then spent 1966 to 1968 with Wes Montgomery. Montgomery's death in 1968 sent Hart to New York, where he became one of the busiest freelance drummers in the city almost immediately. Within a year he was on Pharoah Sanders's Karma for Impulse!, and over the next few seasons he recorded with Eddie Harris, McCoy Tyner, Wayne Shorter (Odyssey of Iska, 1971), Joe Zawinul (Zawinul, 1971), Marian McPartland, and Joanne Brackeen.

From 1969 to 1973 Hart held the drum chair in Herbie Hancock's sextet, the band known by Hancock's Swahili name, Mwandishi. Percussionist James Mtume gave every member of that group a Swahili name, and Hart's was Jabali, meaning rock. It stuck: he is still billed as Jabali on record sleeves and in concert programs, and Discogs lists a dozen different Jabali spellings among his name variants, from "Jabali Billy Hart" to the misprinted "Jaboli Billy Hart." The Mwandishi band produced Mwandishi (1971), Crossings (1972), and Sextant (1973), three records that pushed a working acoustic sextet into electronics and open form without abandoning swing. In the same stretch Hart played on Miles Davis's On the Corner (1972). He left Hancock for McCoy Tyner's group in 1973 and 1974, then spent 1974 to 1977 with Stan Getz, and in 1974 made his first ECM appearance on Bennie Maupin's The Jewel in the Lotus.

Hart's own leader catalog began in 1977 with Enchance on A&M's Horizon imprint, recorded February 24 and March 3 that year with Oliver Lake, Dewey Redman, Hannibal Marvin Peterson, Eddie Henderson, Don Pullen, Michael Carvin, and two bassists, Buster Williams and Dave Holland, splitting the tracks between them. Holland returned for Oshumare (Gramavision, 1985), an electric, multi-guitar date with Branford Marsalis, Steve Coleman, Bill Frisell, Kevin Eubanks, Kenny Kirkland, and Didier Lockwood, and Hart kept that larger, denser sound for Rah (Gramavision, 1988). Through the 1980s he was also a founding member of Quest with David Liebman, Richie Beirach, and Ron McClure, a cooperative band that recorded across three decades. Two Arabesque albums, Amethyst (1993) and Oceans of Time (1997), sharpened a working group around John Stubblefield, David Fiuczynski, Mark Feldman, and Santi Debriano, with Chris Potter added on the second. From 1993 Hart also spent roughly a decade in Charles Lloyd's quartet, recording The Call, All My Relations, Canto, and Lift Every Voice for ECM.

Teaching became a second career from the early 1990s. Hart is Associate Professor of Jazz Percussion at the Oberlin Conservatory of Music and also teaches at the New England Conservatory of Music and Western Michigan University, with private students through the New School and New York University. He published the instructional volume Jazz Drumming through Advance Music in 1988, and he is a regular at the Stokes Forest Music Camp and the Dworp Summer Jazz Clinic in Belgium. Since the 2000s he has been the drummer in the Cookers, the veteran septet organized by trumpeter David Weiss around Eddie Henderson, Billy Harper, George Cables, and Cecil McBee.

The band that now carries his name came together in 2003: Mark Turner on tenor saxophone, Ethan Iverson on piano, and Ben Street on bass. They recorded Quartet for HighNote in October 2005, then moved to ECM, where Manfred Eicher produced All Our Reasons (2012), One Is the Other (2014), and Just (2025). Hart's first live album under his own name, Multidirectional, taped at Smoke in New York over four nights in December 2023, followed on Smoke Sessions in November 2025. He was named a National Endowment for the Arts Jazz Master in the 2022 class alongside Stanley Clarke, Cassandra Wilson, and Donald Harrison Jr., and a Mellon Foundation Jazz Legacies Fellow in 2025. His oral autobiography, Oceans of Time: The Musical Autobiography of Billy Hart, assembled from interviews by Iverson, was published by Cymbal Press in 2025 and launched at the Village Vanguard that July. He lives in Montclair, New Jersey, and remains active as a leader, sideman, and teacher.

Hart's reputation rests on adaptability rather than a signature lick: the NEA's citation calls him one of the most sought-after drummers of his generation precisely because he moves between straight-ahead, avant-garde, and pop settings without changing his fundamental approach. What carries across all of it is cymbal work, a light, continuously varying wash that reviewers and producers describe as tracery rather than timekeeping, and a habit of shading a soloist's line instead of marking the bar. Manfred Eicher has cited Hart's dynamics and cymbal sound as the reason he tracked him from the 1974 Bennie Maupin session onward, and Charles Lloyd built a decade of quartet records around exactly that quality. Hart himself frames the matter in terms of rhythm's standing, arguing that rhythm is at least the equal of harmony in human development. His mentors were not drummers: Buck Hill and Shirley Horn, both Washington figures, shaped his musicianship first, and the Mwandishi years with Herbie Hancock taught him to hold a groove while the harmony around it dissolved. That combination made him a first call for two constituencies that rarely overlap, the hard bop mainstream and the ECM and loft-era avant-garde, and it is why his sideman log runs to several hundred sessions across six decades.