The phrase that Ragman quoted in the original request:

"...the kind of song that starts today and goes on till tomorrow..."

sounds strangely familiar to me. ("Strangely familiar"—is that a contradiction?)

However, when I heard it, I doubt that it was "Hebridean song"; it might have been "old-fashioned song" or "old Scots song" or something like that.

Ragman: Is there any possibility your uncle took a popular song and changed it? Is that the kind of thing he would do? Does your family have any connection with the Hebrides? Is there any reason he would want the song to be about the Hebrides, even if when he heard it it was about something else?

On the other hand, maybe my mind is playing tricks. Maybe I don't really remember the song, but I just remember seeing this thread sometime in the last 5 years, and trying to find the song, and failing.

Anyway, I failed again.