WAV, several of MacColl's songs have famously been collected from the tradition, having undergone a degree of change which qualifies them to be considered as "folk music" under the 1954 definition.

All songs and tunes were composed by someone. To fall back on one of your earlier examples, "Barbara Allen" has been collected in many variants from around the British Isles and beyond. Suppose a researcher were to come across manuscript of the original version, with the name of the composer. Would it cease to be a "folk song"? Not under the 1954 definition.