Maybe it's because I write songs, but I make a point of learning the correct words when I sing someone else's song. That is, if they are living. I take more freedom with "traditional" songs, because the recording I'm likely to learn it from is one variation that an individual has probably changed to his or her liking. How can I get nervous about changing the lyrics to a traditional song that has almost as many versions as recordings. But, unless I find a line awkward to sing, I still sing traditional songs the way that I've heard them by an individual. Even exceptions there, as someone said. I'll sometimes take one version and insert a verse of to from another version that I really like. Sometimes (although rarely) I'll write an additional verse to a traditional song if I have a "good" reason... it's just a fragment of what was undoubtedly a longer song and another verse might make the whole song make more sense. As for my own songs, I don't write folk songs. I write songs. I one or two of them over many, many years slowly evolve into something a little different, I'd just be pleased that people enjoyed them enough to carry them on. The dead don't know. :-)

Jerry