The A7 chord—also known as “A Dominant 7″—is an important guitar chord for you to know. Below are two fingerings for an A7 guitar chord. We feel the best way to understand chords is to understand where they come from, as well as how use them in a musical context. In this article, you’ll learn the following:
- What is an A7 chord?
- Guitar chord fingerings for an A7
- How to use A7 chord shapes in a blues chord progression
A7 Guitar chord shapes
What Is An A7 Chord?
An A7 is what is referred to as a “Dominant Seventh” chord. Without getting too far into the weeds of music theory, a Dominant Seventh chord is a 4 note 7th chord built from a Major scale, where the 7th note of the scale is flattened 1 half step (1 fret in guitar terms). Example #1 (left, above) is fingered at the 2nd fret, and utilizes open strings. The root of the chord is A, which is the open 5th string. Example two is fingered on the fifth fret. This time, the root note of A is found on the 6th string, 5th fret.
Dominant Seventh Chord Formula
A scale degree is the position that a note appears in a scale. Based on the Major Scale, a Dominant Seventh Chord contains the following scale degrees:
1st (root note)
3rd (Major 3rd)
5th (Perfect 5th)
b7th (Flat 7th)
Notes in an A7 Guitar Chord
As we saw above, the scale degrees of an A7 chord are 1, 3 ,5, b7. These equate to the following notes on the guitar:
1st: A
3rd: C#
5th: E
b7th: G
These intervals will be the same for any dominant chord, but the notes will be different. For example, the notes of a D7 and E7 chord will consist the same major scale degrees as an A7, but the actual notes will be different because they are derived from their respective major scales (D Major and E Major).
What is the sound of an A7 Chord?
You can think of a Dominant Seventh chord as a Major Chord with an added flat 7th note. Dominant chords sound similar to a Major chord, with added tension from the the b7th note. In an A7 chord, this note is a G.
The flat 7th of a Dominant chord creates what is referred to as a “Tritone” interval between the b7th (G) and the Major 3rd (C#). Tritones have a very recognizable sound, and the combination of the Major 3rd and the b7th is what gives Dominant chords their characteristic sound.
The sound of a Dominant Seventh chord is often characterized as a chord that feels as if it wants to “resolve”. Put another way, the the sound of the chord is not “restful”, and because of this your ear seeks to have the harmony move to another chord. This is the basis of the tension and release concept in music.
Difference Between Dominant 7th Chord and Major 7th Chord
Do not confuse a Dominant Seventh chord with a Major Seventh Chord, as they sound very different. A Major Seventh chord is a Major chord with a “natural” 7th, instead of a flat 7th. In an A7 chord, this note is a G. In a AMaj7 chord, this note would be G#.
How is an A7 Chord Used in Music?
A7 is an example of a Dominant Seventh chord, and quite simply, they are used everywhere: Rock, Blues, Jazz—you name it. The best way to understand how a chord sounds is to get it under your fingers so you can play it, and the best way to do that is to place it in a musical context. One of the most popular uses for dominant chords is in Blues progressions, and the most fundamental blues progression is what is known as the “Twelve Bar Blues.”
The 12-Bar Blues Progression
The 12-Bar blues is by far the most popular and blues chord progression. A 12-Bar Blues gets its name due to its sequence of chords, each played for a certain number of “bars”. In musical notation, bars refer to a unit of time that contains a specific number of beats, and a 12-Bar Blues has 12 bars. At the end of Bar 12, you repeat the progression.
Twelve Bar Blues Formula
Now that you know the formula, let’s look at a the chords in a Twelve Bar Blues in the key of A Major. The progression consists of three chords: A7, D7, and E7. These are the I, IV, and V chords of the key, which in this case is A Major. These are all dominant seventh chords, and can be moved up the fretboard and fingered like A7. In this 12-Bar Blues example, A7 is played for 4 bars in the beginning, and the D7 is played for (2 bars), beginning in Bar 5. In bar 9, you play an E7, then D7, for one bar each, then it’s back to A7. Written out, it looks like this:
A7 is played for 4 bars
D7 is played for 2 bars
A7 is played for 2 bars
E7 is played for 1 bar
D7 is played for 1 bar
A7 is played for 1 bar
E7 is played for 1 bar
Here is the 12-Bar Blues Progression written out, as you would see in a chord chart:
Here’s a trick to remember the 12 Bar Blues format: The first chord—A7—is played for 4 bars. Then, the next two chords (D7, and A7) are each played for two bars each, which is half of the first chord’s duration. When you get to the E7 in the 9th bar, each chord is played for one bar, which again is half of the previous section.
Summary
Keep in mind there are many ways to play an A7 guitar chord. However, you only have to know one of them to get going. The Twelve Bar Blues featured here is a great way to get get Dominant Seventh chord grips under your fingers. Check out our articles on D7 and E7 to learn the chord shapes for the other two chords needed to play a 12-Bar Blues in A Major.
When you feel confident and can make the changes for A7, D7, and E7 smoothly, move on and explore other voicings of dominant chords. Being able to voice a chord in multiple ways will add color and variation to your rhythm playing. Eventually, when you know multiple ways to play an A7, you’ll be able to mix and match. This will lend interest and harmonic content to your chord playing.
Happy Playing!