I know this doesn't address the original question, but I've just seen this at the online Globe and Mail:

A study into the roots of gospel music by a U.S. professor -- an accomplished musician who has played with Duke Ellington and Dizzy Gillespie -- has led him to conclude that the "good news" music sung in black American churches originated in Scotland, not Africa. Willie Ruff of Yale University said the roots of the music derived from evangelical spirituals and had more to do with the crofters of the Outer Hebrides than slaves on U.S. plantations. Prof. Ruff, 71, a Baptist from Alabama, told Britain's Independent newspaper: "I, like everyone else, assumed [the music] was unique to black congregations in the United States . . . but I began to wonder if it was performed by white congregations in the same way." He discovered that some black U.S. slaves owned by Scottish immigrants spoke only Gaelic. However, it wasn't until he travelled to Scotland, and heard psalm singing in Gaelic, that he became convinced of the common roots: "I was struck by the similarity, the pathos, the emotion, the cries of suffering and the deep, deep belief in a brighter, promising hereafter."

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I think he's being just a teeny bit simplistic here ...

sian