I'm sorry it took me 7 months to respond to this thread, but I think it was going on during the time I was having major computer problems and then I forgot. Anyway, Sandy has asked me to add a few comments.   

In certain areas of NC, the Scottish Gaelic speakers who emigrated in the 18th century were predominant. That would be parts of the eastern and southern parts of the State. This group had nothing to do with the "Scotch-Irish" as they are called here, who were the very early traders in the western part of the state and later comers who mostly migrated down the Great Federal Wagon Road from Pennsylvania.

The Scottish Highlanders came directly to NC from the inner Hebrides, such as Mull, Jura, Islay, Colonsay, Gigha and the mainland opposite this area – Kintyre, and Skye from 1730's to 1805 or so. They were mostly Presbyterian – an important point when you wonder what happened to their music.   Gaelic was spoken for 2 – 3 generations, mostly regenerated by later emigrants, usually relatives of the earlier ones. By the mid 1800's Gaelic was dying out due to various things, probably the influence of other ethnic groups living nearby, and inability to get Gaelic speaking ministers to come to NC.   Fiddle playing and dancing was greatly discouraged there by the ministers by the beginning of the 1800's. Bagpipes were played for some period of time as a few have been handed down in families, although the current owners don't play them.

It has been very hard to find traces of their (Gaelic) music so I believe there was a gap in time between the Gaelic music (such as still exists in Cape Breton) and the old time, mountain or bluegrass music found in NC today. They still play Soldier's Joy and Miss MacLeod's Reel, but they learned it from other musicians, not from parents, grandparents, etc. in a continuing stream. There is a very good article by Larry Bethune from the Berklee College of Music, Boston, in which he traces the tunes of songs back to their origins. He didn't find many traces of Gaelic tunes, however, in current folklore. This paper was published in The Argyll Colony Plus, the Journal of the NC Scottish Heritage Society, within the last year, I think, but I don't have the reference at hand.   Another reference you might find of interest is an article by Rob Gibson called "Cowboy Celtic" in the Folk Tradition, 27, June/July 1998. If it's still available, this info was at: www.folkmusic.net/htmfiles/inart414.htm.   

I have not been able to find a single mention of any Gaelic Psalm singing in the churches in the NC records. Charles Dunn and Michael Newton say "they must have" done it, but no one has come up with proof. It stands to reason that they did sing the Gaelic Psalms for awhile and probably through the style of "presenting", but if all the ministers except one or two in the earliest days were English (only) speakers, you can imagine it probably stopped very soon.

It will be interesting to see the Scottish TV documentary films which will be released in February (one Gaelic, one in English) which explores Willie Ruff's theories. Part of this documentary was filmed this summer in NC and part was filmed in the island of Lewis.
Anne