Bruce Hornsby may have seemed like an unlikely figure to find onstage with the Grateful Dead, since he'll always be best known for the 1986 pop hit "The Way It Is." But it was practically a moment of destiny.

He was a life-long fan, going back to an early stint in Bobby Hi-Test and the Octane Kids, his brother Bobby's Grateful Dead cover band. Hornsby had also already opened for the Dead a number of times and welcomed Jerry Garcia for a guest turn a recent studio album.

Grateful Dead keyboardist Brent Mydland accidentally overdosed and died, leaving the group with a hole in its lineup during a run of shows at Madison Square Garden. Hornsby took over on a provisional basis on Sept. 15, 1990, in a moment he still hadn't completely processed decades later.

"It's as if you painted yourself into the mural that you were looking at as a kid," Hornsby told the (Newport News, Va.) Daily Press in 2015. "It's like you painted yourself into the poster on your wall – and then realized it was real life."

In a sign of their deep respect for Hornsby, the Dead contacted him about filling in for Mydland almost immediately. Rumors had already become widespread among the group's close-knit community.

"The morning after he died, I was in Seattle walking down the street and someone came up to me on the street – Brent hadn't been gone nine hours – and someone came up to me and said, 'Hey Bruce, you joining the Dead?'" Hornsby told The Wall Street Journal in 2015. "It was so insane. The next week, Garcia and Phil [Lesh] came to my show at the Concord Pavilion and asked me to do it."

He never formally joined the Grateful Dead, but ended up playing more than 100 shows over a 19-month span until the group officially replaced Mydland with Vince Welnick. The learning curve, Hornsby admitted, was steep.

Watch Bruce Hornsby's First Concert With the Grateful Dead

Hornsby had more recently incorporated some of their songs into his own band's sets, but he never dove completely into the Grateful Dead's massive back catalog. Any initial rough patches were smoothed out, however, by a long-held sense of camaraderie that went back to the first opening gig in May 1987 at Laguna Seca at Monterey, Calif., in the heady days after Hornsby's debut album hit.

"The Dead heard that there was this band riding around the country playing Dead songs, and Garcia and Phil became fans of the record," Hornsby said in Garcia: An American Life. “So, we got a call saying they wanted us to open a couple of shows."

The next summer, Hornsby shared the stage with them again at Ohio's Buckeye Lake Music Center, playing accordion on "Sugaree" and "Stuck Inside of Mobile With the Memphis Blues Again" to Garcia's conspicuous delight. More collaborative dates followed in 1989 and 1990, around the time Garcia guest starred on "Barren Ground" and "Across the River" from Hornsby's A Night on the Town.

“My band opened for the Dead in Louisville and Raleigh a couple of weeks before Brent passed away," Hornsby said in Garcia: An American Life, "and I sat in with them a bunch and had a great time."

Still, joining the Grateful Dead lineup was something different entirely. "When I came in winging it off the street with no rehearsal at Madison Square Garden in September 1990, I knew about 30 or 40 Dead songs," Hornsby told The Wall Street Journal. "It meant that I didn't know about 130."

Listen to Jerry Garcia Sitting in With Bruce Hornsby on 'Passing Through'

The Grateful Dead played "Gimme Some Lovin'," one of Mydland's signature covers, for the first and last time without him during Hornsby's debut concert. After that, Hornsby began to emerge as a more prominent onstage presence.

At the same time, his relationship with Garcia continued to deepen, both personally and musically. "On the bus rides, Garcia and I would sit together and we'd just talk about music," Hornsby told The Wall Street Journal. "He was really a walking encyclopedia of folk music. He knew the territory so intimately and deeply. He was basically giving me a music lesson every day. I thought I was fairly well-versed in that music but realized I wasn't once I started hanging with him."

By 1992, the pull of his own career – and the continued emergence of Welnick – led Hornsby to other projects. But he never really left the Grateful Dead's orbit.

Hornsby invited Garcia to participate on 1993's Harbor Lights, then he inducted the Grateful Dead into the Rock & Roll Hall of Fame, where Hornsby took part in an energetic update of "Scarlet Begonias" before Garcia died in September 1995. He'd made a series of guest appearances in the meantime, memorably appearing that June at RFK Stadium during the Dead's final tour.

He also took part in the '90s-era Dead-related Furthur Festivals, then enthusiastically joined the group's surviving members for their career-closing Fare Thee Well reunion shows in 2015. "There was never anything like a Grateful Dead concert, and there probably still isn't," Hornsby told the Daily Press. "That was the archetype of the jam artist. That was the paradigm."

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