Reminds me of another story but US Americans. The songs were passed on and that's how they found the link. I think it was to Sierra Leone in that case, too. Very interesting.
*Found a reference on Wiki: "In the Americas, especially the United States, researchers have discovered that elements of African culture had long persistence. In some areas where there were large groups of enslaved Africans, they kept much of their heritage. In the 1930s African-American linguist Lorenzo Dow Turner found a Gullah family in coastal Georgia that had preserved an ancient song in the Mende language ("A waka"), passing it down for 200 years. In the 1990s three modern researchers -- Joseph Opala, Cynthia Schmidt, and Tazieff Koroma — located a Mende village in Sierra Leone where the same song is still sung today. The story of this ancient Mende song, and its survival in both Africa and the US, is chronicled in the documentary film The Language You Cry In." I think I had the movie downloaded because the granddaughter ends up going back. It was really touching, you can see how the impact on her but also the people she met with when she went there.