Jim Lad,
A number of years ago (before Google) I began to wonder why my father was an Mc but his brother was an Mac and also why was the small c on the upper line and not on the same 'level' as the ean?
Reading a few 18th and 19th century book showed me that the printers' convention at the time was to use an apostrophe in place of Mac. All MacDonalds, MacLeans, MacGibbons were in fact M'Donald, M'Lean and M'Gibbon. This would explain why it was printed above the line. It would be just as easy to write a small c. On closer examination I found that the apostrophe was in fact an open quote which looks like a small c, the reverse of the apostrophe. And so this was in time seen as a small c on the upper part of the line. In my family's case, it appeared that my grandfather just allowed the registrar to fill in the certificate on both occasions (he was very fond of his whisky). My great grandfather was from Mull and spelled his name Mac! Like you I am called either Jim, James, etcetera but this has no relevance on the Mc V Mac question. I don't see how you can just say I'm wrong.
Regarding the chords to Glencoe, I leave that to the singer/player as I wrote it as a melody line. At the time of writing, about 45 years ago, I lived in a tiny room and composed most of my songs using an English concertina!
Thanks for all your kind comments.