Often the early song collectors who actually wrote down the tunes (many of them didn't, interested only in "ancient poetry") assumed that the singers were unschooled musicians and if they heard what they thought was a "wrong note," they'd write down what they thought the note should have been. Cecil Sharp was one of the first collectors to write down the notes he actually heard.

Examining the tunes later, he made the discovery that the old ecclesiastical modes from centuries past were still alive and well and living among traditional singers. The singers were not singing "wrong notes," they were singing the notes they intended.

Don Firth