This is a really beautiful song. I hadn't worked on this song at all, but your post inspired me to do so! I haven't spent much time with it yet, so pardon any mistakes in my transcription of the guitar part (I hope the photo I uploaded works).
The structure of the song seems to be a basic 12-bar blues in G with some interesting harmonization. I think Jim is playing a descending line of dyads that ultimately lead to a G major chord. If you look at bar 2, you see a chromatic walkdown in the bass notes from C to G with harmonized thirds above them. This same walkdown is repeated throughout the song (in bars 6 and 10) and the notes differ slightly in bars 1, 5, and 9 to imply the I-IV-V chord changes of the 12-bar blues. A G7 (I) chord is implied in bar 1. A C7 (IV) chord is implied in bar 5. And a D7 (V) chord is implied in bar 9.
Comments
The structure of the song seems to be a basic 12-bar blues in G with some interesting harmonization. I think Jim is playing a descending line of dyads that ultimately lead to a G major chord. If you look at bar 2, you see a chromatic walkdown in the bass notes from C to G with harmonized thirds above them. This same walkdown is repeated throughout the song (in bars 6 and 10) and the notes differ slightly in bars 1, 5, and 9 to imply the I-IV-V chord changes of the 12-bar blues. A G7 (I) chord is implied in bar 1. A C7 (IV) chord is implied in bar 5. And a D7 (V) chord is implied in bar 9.
-Ari