Corrected entry: Whenever Montrose appears the soundtrack plays the (irritating) tune to a song called "Bonny Dundee". I assume the film-makers thought there was some connection between the Earls/Dukes of Montrose (whose family name was Graham), and John Graham, "Bonny Dundee" (killed 1689). There wasn't.
Corrected entry: Mary MacGregor (Rob's wife) is the real name of Jessica Lange, the actress who portrayed her.
Correction: No it's not, her birth name is Jessica Phyllis Lange.
Correction: Maybe, but we don't know for sure. It might have been used for a completely different reason.