When you are talking about tradional tunes, there is no original recording, and no way to know how they were written----chords are just block of notes that harmonize with the melody, and you can harmonize any melody just about any old way you want, depending on the sound you are looking for--In another thread, talked about playing the main melody of "Blue Moon" using only one chord--instead of sounding simple. it sounds very out there and jazzy--when you think about it, anything you play on a five string banjo can be considered to be a one chord tune, because the drone/root is always the same--