Just watch out if you work from a fake book, many get around copyright by deliberately putting one wrong chord in somewhere, just so they can say "all music can claim to be the right notes, but not necessarily in the right order." At what point does the accompaniment of two texts in the same verse metre converge to become plagiarism, or diverge because the tone of the words sends the pitch somewhere else? Hymn books have entire sections at the back designed to help choirmasters get away from always singing some favourite hymn to the same old tune, or to put an unfamiliar set of words to a tune the congregation is comfortable with. There are one or two apocryphal examples in the folk world too of transcribing from the next tune in the book too...I diverge, though. Sometimes easing a familiar chord makes things more interesting, quite apart from being necessary: there's nothing worse than the same accompaniment for all 116 verses of Chevy Chase. The moral? Don't be too wedded to the dots. Make the tune your own. And then it will be folk.