By 1968, rock music was changing, and no one — not musicians, fans or promoters — knew where it was going.

"There were no road maps at the time," said pop culture archivist and curator David Beiber. "It was making up the rules as you went along."

Far from the Top 40 radio airwaves, bands like the Grateful Dead in San Francisco and The Velvet Underground in New York were steadily beginning to push at the boundaries of what popular music could be.

Quietly, it was happening here in Boston too.

"Boston, in a way had as important a social, political, musical, cultural scene as New York, San Francisco," said Bill Lichtenstein, formerly of WBCN, who’s working on a film about the Boston music scene during that era. "And yet it’s notoriety, the extent to which it’s been chronicled and the public is aware of those things, falls far short."

Boston’s famed folk scene of the early 1960s was giving way to something wholly new. Free publications like Boston After Dark — a forerunner to The Boston Phoenix — were treating new music as serious art, and a vibrant music club scene was starting to hit its stride.

"There were so many local clubs," Lichtenstein recalled. "You could go out on a Friday and Saturday night and sometimes on the weeknights and just have your pick of some of the great music in the world in town, all playing small clubs."

But it was in 1968 that an undisputed king emerged among them: A former Unitarian Meeting House on East Berkeley Street in the South End, rechristened as The Boston Tea Party. "When it opened, it was the first rock dance hall like it on the East Coast," Lichtenstein said.

Predating New York City's famed Fillmore East, the 400-capacity, all-ages venue hosted a mix of local and national artists, blues masters, and British invasion acts that today reads like a who’s who of rock royalty. Acts including Led Zeppelin, Grateful Dead, Fleetwood Mac, Eric Clapton, Jeff Beck, Van Morrison and The Kinks all played The Boston Tea Party. So did blues icons like B.B. King, Howlin’ Wolf, John Lee Hooker and Buddy Guy.

The aim was music discovery, which often meant strange and surprising band pairings. Jazz great Rahsaan Roland Kirk opened for The Who. Muddy Waters opened for The J. Geils Band. Roots-rockers The Allman Brothers opened for urban-psychedelics The Velvet Underground.

In the spring of 1968, that mind-expanding ethos was sprung from the stage onto the air waves, with the launch of Boston’s first FM album-rock radio station, WBCN. It broadcast from a back room at The Boston Tea Party.

"One of the defining statements was 'ugly radio' is dead,'" Beiber said. "And that was referring to Top-40 and any other radio that they considered inappropriate."

Lichtenstein compared WBCN to the best of today's social media, because the station "saw itself as a conversation with its listeners."

Young, tastemaker deejays, mostly freed from any format contains, began bringing album cuts, obscure and unsigned artists, political discussions and long-form interviews to the masses. Lichtenstein said it was nothing short of transformative.

"What happened in 1968, it helped create a scene here, which really nurtured and incubated great music," he said.

From this cauldron emerged a slew of local bands that would put their mark on music history through the 1970s — from Aerosmith to Boston, The J. Geils Band to The Cars.

"You know these are all bands that because somebody at 'BCN heard them, and started playing them ... were able to break through," explained Lichtenstein.

The Boston Tea Party would move to new digs on Lansdowne Street before closing for good in 1970. WBCN would last longer, playing rock music in one form or another into the 21st century.

"I think it’s a period that was filled with adventure and breaking down barriers, and it kind of opened the flood gates," Beiber said. "It showed, in a lot of respects, that self-expression could kind of rise above the rules."