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If I take a standard A minor chord as a barre chord on the 5th fret of a guitar and play it but move my pinky from the root note A on the 7th fret and move it to the 8th fret, I get a dominant chord sounding chord. Essentially it is an Aminor with a min9th... is this called a minor 9th chord? and why does it sound like a dominant chord?

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  • b9 chords contain a tritone (between the 5th and the b9), whose sound is very recognisable and prominent to the ear (and sounds dominant7 to you!).
    – moonwave99
    Feb 5 at 22:49
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I would call it Am b9 (A minor flat nine), it sounds like a dominant, because it has the notes of a C dominant chord, something like "C7 add 6 omit 5 / A" and it resolves to an F chord. If you leave out the bottom A note, it's a nice dominant for F.

Edit. At least in some kind of theoretical thinking, a "b9" chord tension means that "there is a ninth", and because there is a ninth, there should also be a seventh, because chords are - in theory - built from stacks of thirds. To explicitly state that one of the notes in the stack are missing, words "add" and "omit" can be used. For example "C add 9" would mean that there's a root, third and fifth, but no seventh. Or "C9 omit 3" would mean that there's the root, fifth, (flat) seventh and ninth, but no third. In practice however, some chord notes are routinely omitted. In 11 chords the third is omitted so systematically that it's even "officially" stated in some theory material, and the chord is in practice used as a jazzier sus4 chord. In 13 chords, the 5h, 9th and 11th might be left out either because they add too much mud or because e.g. the guitar simply doesn't have enough strings and guitarists don't have enough fingers to play theoretical 13 chords.

For "b9" and "#9" ... is there a 7th in the chord? In the Hendrix chord E7#9, it is explicitly stated that there is a 7th in addition to a 9th. So if you leave out the 7, "E#9", then wouldn't it be reasonable to assume that there is no seventh?

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  • great thanks, makes sense, and it is nice if you want to make a minor chord sound like a dominant chord :)
    – armani
    Feb 5 at 10:15
  • "C7 add 6 omit 5 / A" Normally the chord symbol would be just C13 (or C13/A) Feb 5 at 10:27
  • @user1079505 True, especially on the guitar that's a commonly used approximation, even though it lacks the 9th. Feb 5 at 10:31
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    Just to add to the OP's original thought an A-9 chord would be (A, C, E, G, B).
    – user50691
    Feb 5 at 12:29
  • @armani: instead of saying thanks you can vote up (arrow up) the answers that make sense to you, and the best and clearest one you can accept. Feb 6 at 9:20
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From your description, the chord is based on the A minor triad (A, C, E), with an added Bb, the minor ninth. The correct label for the chord would be Am (add b9). It is probably better to call it "add b9", instead of simply "b9", since that may be taken to imply the presence of a flat seventh, which you don't have. That said, since this chord is not used as often, you'll find that some people notate it one way, and others the other way.

Why does it sound like a dominant chord? Most importantly, there is a tritone between E and Bb. The tritone is the characteristic (tense) interval of dominant chords (at least if you use the word "dominant" mostly in a jazz sense).

As in one of the other answers, you should compare your chord with C7. C7 contains C, E, G, and Bb. Your chord contains C, E, A, and Bb. So the fifth of C7 (a G) has been swapped for an A. Overall, this is not that big a difference, since the two chords have roughly the same intervals:

Am (add b9) has:

  • 1 semitone interval (A - Bb)
  • 1 whole tone interval (Bb - C)
  • 1 minor third interval (A - C)
  • 1 major third interval (C - E)
  • 1 tritone (E - Bb)
  • 1 fourth/fifth (A - E)

This pattern is also referred to as the all-interval tetrachord. "All-interval" because it contains each interval type exactly once, "tetrachord" because its a chord with four (tetra-) notes.

C7 has the following intervals:

  • 1 whole tone interval (Bb - C)
  • 2 minor thirds (E - G and G - Bb)
  • 1 major third (C - E)
  • 1 Fourth/fifth C - G)
  • 1 Tritone (E - Bb)

So these chords have a lot in common, which is why they sound alike. That said, using different root notes and inversions can make a big difference to the ear. Using A minor and then sneaking in the minor ninth as a color note is a more subtle way to evoke a tritone dominant than simply going for C7. Good luck with your discovery process!

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  • If b9 means the existence of a 7th in addition to a 9th, then isn't the chord name "7#9" redundant for example in the Hendrix chord, E7#9? And it should be just E#9. Or does this only apply to flat ninths, not sharp ninths? Feb 6 at 9:47
  • That one’s probably an exception because it doesn’t occur within any of the modes of the major scale. Minor b9 is the ninth chord on a Phrygian mode. Finally, the Hendrix chord is in some sense different because it is not created by stacking major or minor thirds. There’s a fourth between the b7 and the #9. Feb 6 at 10:07
  • But are you saying that E#9 should be enough to imply all the same notes? Why then are people redundantly saying E7#9? I'm trying to say that the practice of writing chord symbols is not based on a grand unified logical scheme that's universally understood the same way by those in the know. Implying that something is universally "correct" gives a slightly misleading idea, when in reality you'll bump into cultural differences. With the E7#9 name being so widely used, I'd think that it's perfectly reasonable to assume that leaving out the 7 implies that there is no 7th. Feb 6 at 10:28
  • Sure. I’d say that it’s fairly logical, and that the Hendrix chord is an exception to the usual naming pattern, for the reason I’ve already given. The main point is to make sure that the user of the notation is clear on the notes in the chord. Feb 6 at 10:34
  • @piiperiReinstateMonica - good point. E7#9 has always been called that, and I often meet E7b9, but when E9 comes along, the m7 is implied, and in Emaj9 the D# is - not only implied, but expected. Weird..! E add#9 might be a solution, just as E add9 is a well known chord.
    – Tim
    Feb 6 at 12:58
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If I'm understanding correctly, the notes, from 5th string up, are E B♭ C E A, making a kind of dominant 13th chord. C13. Oft-times, a 13th chord needs only the m7 (B♭) and the 13th (A, aka 6) to be a 13th chord. 9th and 11th are routinely omitted. Also the 5 (G) is often left out.

I feel it's a red herring to say there's a m9 in the chord - unless you still want it to be A based. But then the dominant sound won't emanate from it having root A. And, that apart, Am9 is a completely different animal.

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I think your question is really about jazz chord nomenclature.

"Minor nine chord" in jazz would be a minor triad with a major ninth, ex. Am9 called "A minor nine."

"Minor flat nine chord" in jazz would be a minor triad with a minor ninth, ex. Em♭9 called "E minor flat nine."

In Roman numeral, functional analysis the wording can be different.

First, both C: V9 tones G B D F A and Cm: V9 tones G B D F A♭ can be called "dominant ninth chords." The particulars of the major or minor ninth will be understood in the context of the key. Likewise if you have C: vi9 or C: iii9 they both might be called simply "ninth chords" or "submediant ninth" or "mediant ninth" or "A minor ninth" or "E minor ninth." Various wordings like that might be used. Again, the ninth would be understood in the context of the key.

Aminor with a min9th... and why does it sound like a dominant chord?

A dominant should be a dominant to something. I'm not sure how your hearing it as a dominant. It could go two ways...

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...if C becomes C# then it's a dominant to Dm. If you move the A to some tone of a C7, C dominant seventh chord, it's a dominant to F. Without knowing where you would move the dominant sound you hear the generic explanation is it differs from some potential dominants by only one tone.

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An am7b9 chord sounds like a dominant chord because if you don't play the bass tone you have the V7 of the relative chord: I would notate this chord as a V7/and the relative minor root bass tone.

Examples: (not referring to guitar chord shapes!)

EGBDF => G7/E

ACEGBb => C7/A

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