Hi guys, I stumbled on this chord which I really loved the sound of. Just wanna find out what the name of the chord is or if there’s any easier-to-remember name other than what’s in the pic (A9sus4\G was suggested by a website)? & what’s the theory behind it?
(Context: I was practicing fingerpicking Moon River in G major, and I realised in one of the sections, when I replaced normal G with this chord, it actually sounded really nice to me! Hence my interest)
Thank you!
To me, this is a G chord with an A note added, hence Gadd2 (or could be called Gadd9, I suppose).
Yeah, that’s what I was thinking. The A is in the second octave so Gadd9.
There are various options here.
Gadd9 is probably the easiest answer because it ticks all the boxes. Please note it’s not a Gsus2 chord because the 3rd (the note B) is also present.
G major chord (G B D) + 9th interval (A) = G B D A
A9sus4/G can be correct as well. Let’s break it down starting from a regular A major chord = A C# E
To make it an Asus4 chord, we take away the third (C#) and replace it with the 4th (D) = A D E
To make it an A9sus4 chord, we add the flat 7th (G) and the major 9th interval (B) = A D E G B
If we play the G on the thickest string, rather than the root note A, it becomes an inverted (“slash”) chord. Hence the notation A9sus4/G: An A9sus4 chord with the G in the bass.
And to conclude, as is often the case with extended chords, we can leave out some notes that don’t add a lot of harmonic value to the chord. It’s easier to play and it usually sounds better. The first choice is often the 5th (E).
That leaves us with the notes A D G B. The same notes that form a Gadd9 chord.
How you like to call it depends on the context. E.g. in the key of G major, I would just call it a Gadd9. You would encounter A9sus4/G in a Blues/Jazz context.
And some trivia: playing all the strings open (E A D G B E) would be an A9sus4/E chord. 
@Jeff
Great explanation Jeff!
Since my reply, I’ve been wondering if it could have another name as well. I hadn’t worked it out though!
Well there you go Amanda. For your song it’s Gadd9 but you can impress your friends by telling them that you’re playing a blues/jazz chord A9sus4/G 
Got it. Thanks guys!
I’m also currently trying to learn more about what ‘add’ chords are… if anyone can point me to any of Justin’s lessons (if he touches on them) or any other resources, or can give me a beginner’s intro to the theory behind them, that’ll be great! (:
‘Add’ chords are chord additions. They are built by adding extra notes to a triad (a 3-note chord) to give it a different flavour.
The most common ones are ‘add9’ and ‘add11’ chords, where the notes corresponding to the major 9th and the perfect 11th interval respectively are added to the three notes that form the basic triad.
To keep things practical, let’s define the major 9th interval as being the same note as the major 2nd interval. Some would argue they’re an octave apart. Likewise, the perfect 11th interval is the same note as the perfect 4th interval.
G major triad = G B D
Gadd9 = G B D A (the note A being the major 9th interval)
Gadd11 = G B D C (the note C being the perfect 11th interval)
I won’t make things unnecessarily complicated, but a ‘Gadd9’ chord is not the same as a ‘Gmaj9’ or a ‘G9’ chord. These are chord extensions of what Justin calls ‘quadads’, which are 4-note chords (chords containing some kind of 7th interval).
I’ll leave it there for you to explore further when you’re ready for it. Justin addresses chord extensions and the difference with additions in Grade 6 of the Music Theory course.
Justin also touches on this in the new live theory class video. It is a good watch.
Got it. Thanks Jeff for sharing and keeping it simple! (:
Justin calls it Gadd9
