Drummer and percussionist with the Grateful Dead.

Hart was born in 1943 in Brooklyn, New York and was committed to percussion from the beginning. Both of his parents, Lenny and Leah Hart, were champion marching band-style drummers in the 1930s and 1940s. Although his father left home before he was born, his mother encouraged his drumming through lessons in high school, where he too played in marching bands. Nigerian drummer Babatunde Olatunji performed at schools around the country in the late 1950s and had the students try out the drums. Hart was one of those students and he never forgot the experience. Olatunji later taught Hart and collaborated with Hart and the Grateful Dead on a regular basis.

In 1960, Hart dropped out of high school to join the US Air Force. After his discharge in 1965, he was invited by his estranged father to come work in his Bay Area drum store.

Around 1967, Hart was introduced to the Dead's drummer Bill Kreutzmann and the two quickly became friends. Shortly after this, Kreutzmann invited Hart to sit in with the Grateful Dead at a show on 30 September 1967. A legendary Alligator > Caution jam that reportedly lasted two hours ensued. After the show, Hart was invited to join the Dead as their second drummer.

His influence pushed the band into complex, multirhythmic explorations. A student of Ustad Allah Rakha, he added various strains of non-Western music to the Dead's general atmosphere.

Along the way, Hart recommended his father to the band as their business manager. When Lenny was caught embezzling receipts in 1970, Hart decided to take a leave of absence in 1971, although no one in the band held him responsible in any way. During this period, he recorded the album Rolling Thunder. Hart gradually came back into the Dead's performance and recording ensemble, appearing at the final show at Winterland before the band took a hiatus in October 1974. He remained with the Grateful Dead until their final dissolution in 1995 and continues to collaborate with the remaining members under the band name The Dead.

In 2005, Hart and the members of the band Particle joined to create the Hydra Project.

During 2006, Hart teamed up with Kreutzmann, former Phish bassist Mike Gordon and former Other Ones lead guitarist Steve Kimock to form the Rhythm Devils, a nickname that refers to Hart and Kreutzmann's legendary drum solos and improvisation. The band features songs from their respective repertoires as well as new songs written by Robert Hunter.

Over the years, Hart has been involved in many musical and archival projects, most notably the band Global Drum Project. He is the author of several books, including Drumming at the Edge of Magic and Global Drum Project.