The reel-to-reel recordings of the speech at Temple Emanuel in Worcester, about an hour from Boston, were rediscovered in 2013 by Laura Klein-Weiner, the granddaughter of Rabbi Joseph Klein, who invited King to speak there. The speech uses phrases and themes from King’s “I Have a Dream” address delivered two years later in Washington, D.C.

Scholars say the tapes, which have been described as a “historical gem,” show a different side of the civil rights leader.

“I guess I had heard that he had come to the temple, but I didn’t know that the tapes existed,” she told the Boston public radio station WBUR. “So I was frustrated to know that there was a piece of history that we were sort of sitting on.”

Klein-Weiner, who lives in the Los Angeles area, took the tapes to Northwestern University to have them digitized and put on compact discs, then uploaded them to Soundcloud, a free audio host website.

A former Worcester resident, Mark Epstein, heard the recording there and set out to have the recordings available to be played in public schools in the Charleston, South Carolina, area where he currently lives, and in Worcester, the Worcester Telegram reported.

The recordings were used as part of the Black History Month curriculum for middle- and high school classes in the Charleston County School District, Epstein told the newspaper. They reportedly also found their way into high schools across the country.

Tommie Shelby, a professor of African-American studies and philosophy at Harvard, told WBUR that after the hourlong speech, the second hour in which King answered questions on topics including black nationalism, interracial marriage and economic inequality showed another side of him.

“You get a feel for what was often reported by his friends, that he had a great sense of humor, was really good with jokes and quick to make you laugh,” Shelby said. “You don’t always get a feel for that in his speeches, when he’s much more austere and restrained.”