It sounds bright and ringing. “Add” means there is no 7th: the chord keeps the major triad and adds the 9th one octave above the 2nd.
6 moveable shapes, 1 of them drop 2. None has an open string in it, so each one plays every root there is; the dots are degrees, and R is the root.
Pick a root and every diagram below moves to it. Nothing about any of the shapes changes — only the fret they start on, and each one starts somewhere different because they are rooted on different strings.
Showing Cadd9. Every voicing of it, open strings included, is on its own chord page.
The other half of the pair. Pair them with the low E shapes and the hand barely moves: the root a fourth up sits at the same fret on the A string, and the root a fifth up two frets higher.
x-15-14-12-15-x
4 notes · 4 frets
No bass note under it, which is the point rather than a shortcoming: these sit above a bass player instead of competing with one, and they reach the extensions the lower shapes have no fingers left for.
x-x-10-9-8-10
4 notes · 3 frets
The same chord with something other than the root underneath. You reach for one of these because of what the bass is doing, not because of what the chord is — a bass line that walks while the harmony stays put is made of these.
3 in the bass. 3 ways to get it.
3 on the low E string, root on the B string
12-x-12-12-13-x
4 notes · 2 frets
3 on the A string, root on the D string
x-7-10-7-8-x
4 notes · 4 frets
3 on the A string, root on the high E string
x7x788
4 notes · 2 frets
Close position — R–3–5–7 and its rotations — puts four notes inside an octave, which will not fit under a hand on adjacent strings. Drop the second voice from the top down an octave and it does. That is the whole operation, and it is why these exist: four notes, four adjacent strings, no gap to reach over, and the shape slides.
The base voicing only, one per string set. The same drop applied to the chord's other close voicings gives more shapes, but those are inversions of a drop 2 rather than of the chord, and that is a distinction worth more than it costs to explain.
strings 4–3–2–1
3–R–9–5
xx2533
4 notes · 4 frets
Every voicing of one particular add9 chord — including the open-string ones that do not move — is on that chord's own page, linked under each shape above. All the moveable shapes for every quality are on the shapes index, and the major chords as a family are on their own page.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.