The recording is intriguing to Clayborne Carson, a professor of history and founding director of the Martin Luther King, Jr., Research and Education Institute at Stanford University.

"It's hard to know what we're dealing with," he said, "There are thousands of interviews with Dr. King, and it's hard to tell the historical significance of this (one)."

"What is interesting about this is rather than just a transcript, you can hear his voice," he added.

In 1985, King's widow, the late Coretta Scott King, invited Carson to direct a long-term project to edit and publish the civil rights leader's works.

Based on the dates, Carson believes the African trip King mentioned in the recording was his trip to Nigeria. This is what Carson and his colleagues are most interested in.

"The trip to Nigeria is something we don't have a lot of information about," he said, "In Nigeria he didn't do press conferences, didn't do interviews or write letters we know of."