Theory of 7th Chords

7th chords are a beautiful way to color your songwriting, your rhythm playing, and your improv.  They aren’t as nearly as daunting as you’d think. We’re going to just dive into how they are constructed.  First let’s do a little recap of the basic chords that 7th chords are derived from.  

We’ll start with triad chords.  Triad chords are called triads because they consist of THREE notes.  Tricycle, tripod, trilogy….tri means three, hence the name, triad.  

The notes of a scale are sometimes named by their actual notes and sometimes what degree of the scale they are.  If we’re in C major, then the notes would be: C, D, E, F, G, A, B, C.  If we take those letters and translate them into numbers we get: 1, 2, 3, 4, 5, 6, 7, and then when we get back to one in the next octave (it goes back to 1 because we go back to C). An octave is one complete cycle of the notes.

(SCALE DEGREE CHART)   

C  D  E  F  G  A  B  C

1  2  3   4   5  6   7    1

So if I wanted to write down the notes to a C major chord, I would write C, E, G.  OR I could write down what degree these notes are and write 1, 3, 5. The letters are called the notes of the scale, the numbers are called the degrees of the scale.  So, quick test…what degree would a D be?…………if you said 2 you are correct.  What degree would G be………..if you said 5 you are correct. (Just look above at the little chart..look at the letter and what number is below it…see? Easy.) Ok, let’s move on.  

So triad chords are created by taking three notes of the scale and skipping every other note until you have THREE notes.  So, C, E, G is a triad in C.  (notice how we skipped D and F).  Let’s go do D and do the same thing: D, F, A (notice how we skipped E and G).

(TRIAD NOTE CHART) 

C – C, E, G

d – D, F, A

e – E, G, B

F – F, A, C

G – G, B, D

a – A, C, E

b* – B, D, F

C – C, E, G

So these are all the triad chords in the key of C major.  See how you take the first note, then you skip a note, use the next, skip the next, use the next? This is how we get our triad chords.  So let’s take these chords we just wrote down and turn them from their notes to their scale degrees. (turning the letters into their corresponding numbers like we did in the chart at the top)

(TRIAD SCALE DEGREE CHART)

1 – 1, 3, 5

2 – 2, 4, 6

3 – 3, 5, 7

4 – 4, 6, 1

5 – 5, 7, 2

6 – 6, 1, 3

7 – 7, 2, 4

1 – 1, 3, 5

(this is the same chart as the triad note chart above this one, we just turned the notes into their corresponding scale degrees)

So now that we have a sense of how we create our triad chords, we can now add 7th’s to the mix.  It’s really easy.  When you add a 7th all you are doing is taking the 7th note of the chord and stacking it on top of the triad. So if we go back to the very top chart (SCALE DEGREE CHART) if you wanted to create a C major 7th chord, you would just take the C major triad, which would be C, E, G (or 1, 3, 5 in scale degrees) and then add the 7th scale degree….which would be “B”.  That’s literally all you do. 

So                C major     –      C, E, G  (1, 3, 5)

becomes   C Major 7   –   C, E, G, B (1, 3, 5, 7)

All we did is add the 7th scale degree.  See the difference? Just a 7 added on.  So we stick with that same formula of take a note, skip a note, take a note, skip a note, take a note, skip a note, take a note. 

So now that we’ve made a C major 7th chord, what if we wanted to make a C dominant 7th chord?

C major 7 is usually written as Cmaj7. 

C dominant 7 is usually written as C7

Easy. Take the 7th note you added on and move it down once half step.  

So                 C Major 7         C, E, G, B  (1, 3, 5, 7)

Becomes    C 7                      C, E, G, Bb (1, 3, 5, b7)

All you did was take the B (which was the 7) and move it down to Bb (now the flat 7). 

Just a little side note – a major 7th chord gives a warm, dreamy feel.  If you’ve ever heard “Christmas Time is Here” from the Charlie Brown Christmas soundtrack…that song starts off with a major 7th chord.  Maroon 5 has a song called “Sunday Morning” and the third chord in this song is a C major 7.  So that will give you an idea of what it sounds like. 

A dominant 7th chord is a little less dreamy sounding.  It’s sounds more bluesy and you can use them in way more situations.  The Beatles used a TON of dominant 7th chords.  Blues uses lots of dominant 7th chords.  The main riff from the Beatles song  “Day Tripper” is based on a dominant 7th sound.  Dominant 7th chords are usually transition chord but they can be used in almost any situation.  You can think of them as halfway between major and minor so they have a whole lot of different applications that they can be used for, much more than major chords or minor chords.  

If you want to make a minor 7th chord, you would take the Dominant 7th chord and only change one note.  You would take the E (the 3) and drop it one half step to an Eb (b3)

C dominant 7      C7         (C, E, G, Bb)          (1, 3, 5, b7)

C minor 7           Cm7      (C, Eb, G, Bb)         (1, b3, 5, b7)

 

A minor 7th chord is a very funky, cool sounding chord.  ” Use Me” by Bill Withers starts off with an E minor 7th chord. 

So here’s a chord progression to leave you with, that will use all three different types of 7th chords we just went over.   

CMaj7      (C, E, G, B)

Dmin7     (D, F, A, C)

G7            (G, B, D, F)

Play through these chords until they get comfortable.  

CMaj7  |   CMaj7   |   Dmin7     |   G7

CMaj7  |   CMaj7   |   Dmin7     |   G7  

There you have it! There’s a crash course on basic 7th chords.  There are many many more than just this, but for now, just mess around with these and try them in every key you can.  Have fun and rock on.