You find something like that in Scottish transcriptions for exactly one tune: Tullochgorum. It's mixolydian but was consistently printed for 200 years in a major key signature with the flattened sevenths added as accidentals. Whereas for every *other* mixolydian tune in the repertoire, every publisher notated it the simple way. I have never found an explanation; would anybody really be tempted to sing it in major if they weren't warned?

I'd forgotten about Simon Fraser, but his changes to traditional tunes went far beyond changing the mode - fantastically Italianate ornamentation and extending the melodies to impossible ranges. His lifetime project seemed to be trying to prove that the Scottish Highlanders could take on anybody in Europe at the game of gratuitous musical complication.He never said he was recording the way specific people played or sang, though, except for his father. And for all we know his father *did* do the tunes that way.