To Dead fans, Hart has long been admired for his role in providing the rock-steady, at times hypnotic, beat that made the Dead the preeminent jam band of its era. For Hart, rhythm and percussion has evolved into a subject of serious study -- so serious that he sits on the National Recorded Sound Preservation Board at the Library of Congress, and the Board of Trustees of the American Folklife Center.
He produced the critically praised series of record "The World," in which he collected and presented to a wide audience a variety of styles of music from various cultures. His album "Planet Drum" won the first Grammy ever presented for world music in 1991.
He has just published his fourth book on music, "Songcatchers: In Search of the World's Music," written with K.M. Kostyal. Hart proudly points out that his new book is published by National Geographic Books.
"I wish my grandma and grandpa were alive," Hart said in an interview with United Press International, "because they had their doubts."
Like his previous books -- "Drumming at the Edge of Music," "Planet Drum" and "Spirit into Sound: The Magic of Music" -- "Songcatchers" examines the role of music in human life. The emphasis in the new book is on the comparatively brief history of recorded sound.
"We've been capturing sound for over 100 years, when Edison first stumbled onto etching wax," said Hart. "I've been collecting these stories for years. I hadn't thought about writing a book about it until National Geographic said this sounds like an interesting subject."
For Hart, "Songcatchers" is no less than "a history of us as a people, the species -- what we sound like, what we feel like, what our dreams are."
That's a far cry from the tone often taken by social critics who have variously called rock 'n' roll everything from an indulgent waste of time to the devil's own music. After years of study, Hart has concluded that human beings are coded to make and appreciate music, and that the art form is integrally related to the evolution of the species.
"Music is not a luxury," he said. "It is a necessity of life. Every culture has a music. There is no culture that does not make a sound, a reasonable sound."
Hart said music was a vital evolutionary component that allowed the brain to evolve. And -- more than just "a good beat that you can dance to" -- he said music is no less than "the skeleton key to the spiritual domain."
Outsiders might have seen the "Deadhead" culture that grew up around the Dead as an extreme example of social abandon, but Hart saw it as more of a ritual.
"Here we are involved in this amazing ritual with tens of thousands of people every night," he said. "After a while you had to say there's something more to this than the music and the words."
Eventually, Hart decided it was the rhythm -- the vibration -- that gave meaning to the ritual.
"We were explorers on the edge," he said. "We looked funny. We might have smelled funny and we took a lot of drugs."
Hart said Joseph Campbell -- the writer best known for his work in the field of comparative mythology -- once observed that the Dead were "tied at the heart" with their audience.
"This reminds me if the revelries in Greece and Rome," he recalled Campbell saying. "He said you somehow are handshaking with the archaic."
Hart said the best way to understand a culture is through its music.
"Because it tells you what they're really like," he said, "not what they think they are, but how they really are."
Acknowledging that it sounded idealistic, Hart said he believed that if the Israelis and the Palestinians were to make music together, it would have a positive effect on the Mideast peace process.
"I've never been able to hate anybody after playing music with them," he said. "I believe if there wasn't music we would be eating each other."
Hart and the other surviving members of the Dead are hitting the road this year, on a tour that will include guest appearances by Bob Dylan, Willie Nelson and Stevie Wonder. Singer Joan Osborne will join the lineup.
"We're feeling really good about it," said Hart. "We're a strong band. We had to find it again because we hadn't played in seven years," he said. "Grateful Dead music isn't something you can dial up. It's not the notes, it's the spirit of it."
Hart said that making music with his mates is more enjoyable now than it was in the last days of the band before guitarist Jerry Garcia died in 1995.
"He was in ill health and it wasn't that much fun," said Hart. "Now I'm having a blast. When the rhythm is right, everything is right. Everybody's really smiling."
Will the spirit of Garcia will be a strong presence at the band's gigs?
"I can't imagine why it wouldn't be," said Hart. "His spirit will always be around. He's always in my ear and my heart. But he is not here now to play guitar and the music has to go on. Why forget about it? It was one of the most beautiful creations on this planet."