The importance of 7th chords for the blues cannot be understated. The very heart of the blues is rooted in these chords and any guitar player seeking the soul of the blues needs a deep understanding of these chords.
Like many things here at Blues Guitar Institute, we start from the core concepts and build from there. We’ll take that same approach with 7th chords and build them from the ground up.
Before we get on to building these incredibly useful chords, let’s get one little bit of music theory confusion out of the way. When we refer to a 7th chord, we are technically referring to a Dominant 7th Chord. But who wants to say all that? Instead of always saying dominant, we drop it and assume that anytime someone says, “play a 7th chord” – they really mean play a dominant 7th chord.
Kind of like saying, play a G chord. We really mean, G major, but we don’t always say it. Make sense?
Now, let’s build this thing…
Building An A7 Chord
A 7th chord (or dominant 7th chord if you want to be picky) always consists of four notes. The root, third, fifth and flat seventh. I like to write these as a chord formula that would look like this: 1 – 3 – 5 – b7
The numbers at play here are all pulled from the major scale. Most Western music theory – even the useful music theory – uses the major scale as a reference point for almost everything. That’s why I believe that if you don’t know the major scale inside and out you will pay for it every day you pick up the guitar.
Now that we know the chord formula, let’s find the notes that belong in an A7 chord.
Here’s the A Major Scale written out:
A – B – C# – D – E – F# – G#
If we number each note from left to write, we’ll see the A is our 1 or root; C# is the 3rd, E is the fifth. At this point we have an A Major Triad. If you need a review on triads, check out these lessons from BGI:
Chord Theory: An Introduction to Triads
How to Construct a Major Triad
But then there’s this business about the flat 7th. That’s what makes this chord a 7th chord (not too surprisingly).
The 7th is supposed to be G#. But we need a flat 7th. To flatten a note, all we need to do is lower its pitch by a half-step. In this case the G# becomes G. Just plain G (G natural in music geek speak).
So here are the notes of an A7 ( A – C# – E – G )
Check out the TAB for this lesson to see a few versions of the A7 chord that come in handy for a fingerpicking blues player.
Practice Your 7th Chords
The TAB that goes along with this lesson is a great little worksheet for a practice session focused on getting to know your 7th chords. The sheet walks you through some common 7th chord positions that guitarists use often.
I haven’t tested myself on this, but I would be willing to bet that I play a form of a 7th chord just about every time I pick up the guitar. So, these chords are incredibly useful and I urge you to get inside how they’re built. Then, as Doc Watson says…
Practice Like the Devil.