Thought you might like to know of the first time I heard this song, possibly 1961/62, sung by the great Aberdeen ballad singer Jeannie Robertson in the front room of my teacher Norman Buchan. The room was packed and Jeannie stood with her back to the fireplace, commanding the whole space. She sang Matty Groves in a full version, holding individual listeners with a very direct gaze as she shared two or three verses with them -- and you dared not disengage!
When she reached the part of the story where Lord Donald challenged Matty and offered the naked man his better sword, she paused and looked round the room until she saw Norman standing by the door. Then she said, "Well, you see, Norman -- he wis aye a fair man.". And then she picked up the song again and sang it through to the end.
By the way, I was also told around that time (probably by Norman) that Jeannie knew the ballad to another tune but had heard Jean Ritchie at an Aberdeen folk festival and made her own version of Jean's tune!
Love this ballad, and have thoroughly enjoyed this thread.