An open string left ringing against a fretted grip. Because it costs no finger, it sounds a note the closed shape has none left for -- a tension on top, or a pedal root underneath. Either a familiar grip with open strings added, or a shape so sparse the open strings carry the chord. These belong to their key rather than to a shape, so D, A, G and E have many and Eb a handful.
Emadd9 is E, G, B and F# — Em with the ninth added, and no seventh.
It sounds sharp-edged. The ninth grinding a whole step under the minor third is the edge an m9 softens.
Minor tonic — a triad with one colour on it.

| E | G | B | F# |
|---|---|---|---|
| 1 | ♭3 | 5 | 9 |
Also written Em(add9), Emin(add9) or E-add9. The same chord either way; which spelling you meet depends on who wrote the chart.
An open string left ringing against a fretted grip. It costs no finger, so it can sound a note the closed shape has none left for: a tension on top, or a pedal root underneath.
These belong to their key rather than to a shape: they cannot be moved up the neck. D, A, G and E have many; E♭ has a handful.
Emadd9 has 6 of them, on the top four strings, the bottom four strings, strings 6-4-3-2, strings 6-4-3-2-1 and strings 5-4-3-2-1, from the 2nd fret up to the 4th — every inversion the chord has: E in the bass, B in the bass and F# in the bass. The one to learn first is the E shape at the 2nd fret, which is the easiest grip here.
All 10 common shapes as fret numbers, lowest string first. Hover or tap one to see it drawn.
How you get to it. The turn that lands on Emadd9 is F#m7♭5 to B7♭9: the ii and the V of E minor, which is where a minor tonic is usually arrived at rather than simply begun on.
In which keys. Every note of Emadd9 belongs to D major (the ii, the supertonic), E minor (the i, the tonic), G major (the vi, the submediant) and B minor (the iv, the subdominant).
Every note of Emadd9 is in E dorian, E natural minor, E harmonic minor and E melodic minor.
Change one note of Emadd9 and you have Em (drop the ninth), Esus2 (drop the minor third), Esus2sus4 (the minor third becomes the fourth), Em6 (the ninth becomes the sixth), Em69 (add the sixth) or Em7 (the ninth becomes the flat seventh).
Emadd9 is a minor chord — root, minor third, fifth. Minor chords on every root.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.