Since my last posting I have spent over a year researching this subject and wrote a dissertation on it. To summarise very, very briefly:

The McPeake tune to WMT is original, though the words are based on Tannahill's song The Braes o' Balquhither.

Tannahill set his lyrics originally to an air called the Three Carles o' Buchanan which was printed in a music sheet of 1810. This melody was carried throught the oral traditiona but lost its title in the process .. McColl's mother's version is a variant of this air.

The melody commonly sung to this tune was an arrangement by R. A. Smith of a dance tune the Braes of Balquhidder first printed in 1740.

Burns first vocalised the dance tune for Johnson's SMM.

As I said this is a very, very brief summary of a 15,000 piece of work.