for a start his posts are still here.

The third one is a very nice voicing of C(add9).

The notes from lowest to highest are: C-G->D-E The lowest note will always be your root, so you know right away this is gonna be a C chord. The G is the fifth, the D is the ninth and the E is the third(placed an octave higher). Since the ninth is the highest degree, it's what names the chord.

It's considered "add9" in this case because this is what you call a regular major or minor triad with a ninth degree added onto it and nothing else. This differs from a

Cmaj9: C-E-G-B->D (notice there's a major seventh chord in there with the ninth on top)

or

C9: C-E-G-Bb>D (also called dominant 9, notice there's a dominant 7 chord in there with a ninth on top)


But what's more important to note here is not the proper nomenclature, but the nice voicing used. Notice that C, G and D are all perfect fifths apart. This is touching on a concept know as quintal harmony. I won't get into that now in order to avoid writing another novel, but voicings that spread notes out in successive fifths or fourths(quartal harmony)tend have a certain wandering and ambiguous quality to them.

I just checked out the wiki page on quartal and quintal harmony, it has some decent info I guess. There's a small section there on how it was used in jazz. Check out Herbie's "Maiden Voyage" and Davis' "So What". These were the first noted jazz tunes that used this type of harmony. You can hear it in "Blue in Green" too. Bill Evans(the guy on piano in the Davis tunes) always did some beautifully innovative stuff while he was alive.

edit: Just wanted to add, this is my favorite type of harmony to play with. There's something so mysterious, emotional and almost ancient about it. It's the type of harmony used in Zelda games and a lot of other fantasy JRPGs. It's the type of harmony that was explored and cultivated in France in during the 1800's Impressionist movement, with composers like Debussy, Ravel and Satie. It arms with the freedom to do a lot of visual things with music. It's also the reason why this sounds so badass.