Gillespie had long shared with his friends stories of slaves who spoke Gaelic, as told to him by his own parents. The musician led Willie Ruff, retired music professor at Yale University, who played with greats such as Duke Ellington and Miles Davies, to investigate further.
Ruff, a bassist and French horn player, had always been mystified by the line singing of hymns he first heard as a child in the Baptist churches of the American south.
Long struggling to pinpoint its origins, Ruff was led to Presbyterian churches in his home state of Alabama and then, ultimately, to the Wee Free churches of Lewis in the Outer Hebrides in search of the roots of this emotional, stripped back form of worship.
It has been widely held in the United States that the method of praise, where the congregation repeats back a line of a song to those leading the sermon, originated in Africa and then taken to the plantations by slaves.
But Ruff, following his research, believes that the music originated in the Hebrides and Highlands before being transported to the American colonies along with Scots emigrants, some who became slave owners.
Ruff earlier said: “I have been to Africa many times in search of my cultural identity, but it was in the Highlands that I found the cultural roots of black America.
“We as black Americans have lived under a misconception. Our cultural roots are more Afro-Gaelic than Afro-American. Just look at the Harlem phone book, it’s more like the book for North Uist.
“We got our names from the slave masters, we got our religion from the slave masters and we got our blood from the slave masters.”
Although their exact numbers are unknown, records show that vast numbers of Highland Scots migrated to North Carolina during the colonial period.
Among them was Flora MacDonald, the Jacobite heroine, who settled in Cheek’s Creek with her husband Allan, who fought in British loyalist forces during the American revolutionary war.
Scots had been drawn to North Carolina from 1739 when royal governor Gabriel Johnston, a former professor at St Andrews University, encouraged 360 Highland Scots to settle in the state with a ten-year tax exemption later offered as an incentive.
More followed after Culloden, some as convicts later sold as indentured servants, with poverty and Clearances sending new waves of settlers thereafter.
The 1790 Census of North Carolina lists 150 inhabitants of the Upper Cape Fear Valley who named Scotland as their birthplace - with the record listing how many slaves they owned.
By then, James Campbell, of Campbeltown, Argyll, had set up three Presybyterian churches in the area and was preaching in Gaelic with fellow ministers, John Bethune and John MacLeod, later arriving to lead worship in the settlements of Scots.
Historian James Hunter, in his book a Dance Called America, which looks at the emigrant experience of Highlanders in the United States and America, details how Highland settlers in Cape Fear embraced slave ownership.
Hunter wrote: “A census of 1790 found several hundred Afro-Americans in the neighbourhood of Fayetteville, most of them belonging to men with Scottish Highland names.
“Farquhard Campbell, John MacLean, Archibald MacKay, Archibald MacNeil and Alexander MacAlister had 180 slaves between them.
“And many of those slaves, it was noted as a curiosity by travellers to the Cape Fear River region, were distinguished from other North American blacks by the fact that they spoke Gaelic - this being, of course, the everyday language both of their white owners and of practically everyone else in the vicinity.”
Historian David Alston, who has led vast research into the Highlander connections with slavery, said the
Gaelic language would have been used as a form of control by the slave owners.
He added: “The slave trade reduced people to commodities and slaves were traded without regard to family or cultural ties.
“The Africans who were enslaved were from many cultures and language groups - and on any plantation owners would feel safer if there was no common African language through which enslaved people could form bonds.
“Imposing another language was initially a means of controlling people, whether that language was Dutch, English - or Gaelic.”
Gaelic speaking in North Carolina declined after the Civil War and virtually disappeared as a spoken language by the mid-twentieth century.
Scottish surnames, however, have remained common in the state. Bain, Black, Campbell, Clark, Darrach, Gilchrist, McDonald, McDougald, McKay, McLean, McLeod, McNeill, McPhearson, McAllister, Morrison, Patterson, Ross, and Stewart are still prevalent, according to the North Carolina History Project.
To some, the influence of Highlanders on slaves, their language and culture during the 18th Century has left a deep legacy.
Kai Erikson, professor of sociology at Yale University, said in 2013: “It often happens that the most marginalised people in one part of the world bring their customs to the most marginalised people in another part of the world. These customs become a form of defence.”
He said that if the connection between precenting the line in Hebridean churches and line singing in America congregations could be proved, the history of African American music as a whole could be revised.