WHen you take Dirk's wonderful idea back to his playing fretless you see how open the song is to interpritation .. I have played around with this one in 5 tunings and a lot of years .. He is playing in a sawmill tuning with the fifth string down a note and then tuned down for his voice .. (We used to call that CUmberland Gap Tuning .. The chords are pretty straight forward but the wholes song is so open you can do lots of different things to it depending on what you are hearing .. I used a relative minor instead of the sub dominant 5 for years .. Here is a link to a clip on the chords behing the melody to fit with the big band take .. https://www.youtube.com/watch?v=Qt117M4AfHk