Try as I may, I can't seem to figure out the acoustic guitar chords underneath the gorgeous, and totally idiosyncratic, six-note piano solo in this song. It feels to me like there's some kind of harmonic sense to the thing, and although I can't quite get at what's going on, I'll at least lay out what I do know here.
The song is in twelve-eight and is based around an acoustic guitar strumming a C chord on the dotted quarter beats one and two of the measure and a C chord plus an added fourth on beats three and four. The bass plays a C on beats one and two and a G, the fifth, on beats three and four. The song is played slowly enough that the G in the bass on those last two beats doesn't really feel like a chordal tone of C; it's more like there's supposed to be a G chord there, but the guitarist is playing that C suspended chord instead. A little bit of harmonic ambiguity there, and we seem to get it again in the verse when the bass plays an F over what sounds like a D minor seventh chord in the guitar. (F is the third of D minor, obviously, but bass player Spampinato only plays F underneath that chord, as though it's a IV chord).
The piano solo starts with eight bars of the C-going-to-the-C-suspended-chord progression, but the solo melody is mostly repetitions of the note B on the dotted quarter beats. B is just the seventh tone of the scale, of course, and the emphasis on the note adds a major seventh harmonic feel, but it's happening in a place where you wouldn't expect it.* Not only that, but it's happening right on the beat, right along with the C and the F in the guitar and a continued discontinuity with the C and G in the bass.
Have to say, this feeling of three people just playing their own thing at the same time is a little Shaggsian! It also makes complete musical sense, though; the freedom in the bass and the major seventh harmony are...jazz, I guess.
And like I said at the outset, what happens next also feels like it makes sense somehow, but I can't figure it out. The B keeps repeating in the piano melody, but the harmony shifts. We seem to be hearing a B7 chord, under which the bass goes from F# to B (below) and to B (above). It then moves down for a chromatic descent of F to E to Eb, though, and as it hits that last note, the piano melody resolves from the repeating B down to G. With this, we seem to have some kind of Eb harmony (given Eb and G together), especially given the fact that it's followed by a D minor ii chord, perhaps suggesting that it's some type of chromatic upper neighbor.
I've got four questions about all of this. What function does the B7 chord have? What are those guitar chords we hear over the chromatic run in the bass (and how do they help explain the logic of the progression)? What is that chord the chromatic line lands on with the Eb and the G? And exactly how genius is it that Terry Adams devised this structure that supports a six-note diatonic melody that never strays from C major???
* Except from this group, maybe, anyway.