I saw an interesting video the other day, advancing the theory that the roots of bluegrass were African and "Celtic". Same sort of stuff, you know the kind of thing, Scots/Irish immigration into the Appalachians, escaping from the wicked English. well, of course everybody influences each other. There is plenty of pentatonic music in the outer Hebrides, and in Tibet for that matter, not to mention Basildon. Personally, i would say that the distinctive features of the Hebridean religious music are a million miles from black gospel. The harmonies of gospel are obviously 3-chord trick NW european rather than African, but certainly not specifically Hebridean. The sonorities are stunningly un-Hebridean, the language obviously not Hebridean, the melodies not Hebridean. So what is left? However, I shall watch the programme with the greatest of interest, and listen to a few gospel recordings, and my treasured Isle of Lewis psalm tape as well, to prepare myself culturally.