7th Chords are used in a lot of different styles of music, but nowhere are these chords as prominent as they are in blues and jazz music. The theory behind 7th chords is pretty simple, but a lot of guitar players seem to get all flustered by them. If you know the triads (go to the Triads Lesson if you don't know your triads), you should have no problem learning the 7th chords.
7th chords, as the name implies, are built by adding a 7th interval to the four possible triads:
Major: 1 3 5 7 Major 7 C E G B written CMaj7, CM7 1 3 5 b7 Dominant 7 C E G Bb written C7
1 b3 5 7 minor/Major 7 C Eb G B written Cmin/Maj7, Cm/M7 1 b3 5 b7 minor 7 C Eb G Bb written Cmin7, Cm7
1 b3 b5 b7 minor 7b5 or half diminished 7 C Eb Gb Bb written Cmin7b5, Cm7b5, C ø 1 b3 b5 bb7(6) Diminished 7 C Eb Gb Bbb(A) written Cdim7, C º7
1 3 #5 7 Augmented 7 C E G# B written CAug7, C+7, CM7#5
There are some things you need to understand about 7th chords.
In the Triads Lesson, I explain how chords are built by stacking 3rds. This formula holds true for adding the 7th to the chord. That is why you don't find an augmented chord with a b7 (G# to Bb is a 2nd interval) or a diminished chord with a natural 7. (Gb to B is a 4th interval. Check out the Intervals Lesson if you don't know intervals.) Both of these chords are still possible to play, they just have a different name. This is covered in the Extended, Altered and Other Types of chords Lesson(not posted yet).
Dominant chords cause a lot of confusion. This is due to the fact that the "dominant" part is understood rather than written. You will hear a lot of players refer to the majors, minors and "sevens" when they talk about chords. What they are really referring to is major triads, minor triads and "dominant" 7th chords. These three chord types are used in a billion songs, and these players have never learned to distinguish between the good old "7" chord (G7, D7, E7 etc...) and all the other possibilities. Don't make the same mistake.
Diminished chords are weird because you have to distinguish between half diminished and full diminished 7th chords. Not only that, but the full diminished 7th chord has that bb7(called double-flat seven). The bb7 is arrived at by flatting the 7 and then flatting it again. This gives you the same interval as the 6. The bb7 is covered in the Symmetrical Scales Lesson(not posted yet).
The hardest part of learning and using 7th chords (as well as extended and altered chords) is the fact that there is no standard way to write them. In the chart above, I give you a couple of common ways that you might see the chord written in a song book or chord dictionary, but every author seems intent on inventing a new system for naming chords. One guy thinks that major chords should be notated using a triangle, another guy thinks that a plus sign is the way to go, and the third guy uses some Egyptian hieroglyph. The only way around this mess is to know your chords well enough that you can pretty much figure out for yourself which chord is needed.
Now, let's see what happens when we plug 7th chords into the chord scale. (Go to the Chord Scale Lesson if you don't know what the chord scale is.)
Degree Note Triad 7th Chord Name I C C E G C E G B Tonic 1 3 5 1 3 5 7 ii D D F A D F A C Supertonic 1 b3 5 1 b3 5 b7 iii E E G B E G B D Mediant 1 b3 5 1 b3 5 b7 IV F F A C F A C E Subdominant 1 3 5 1 3 5 7 V G G B D G B D F Dominant 1 3 5 1 3 5 b7 vi A A C E A C E G Submediant 1 b3 5 1 b3 5 b7 vii B B D F B D F A Leading Tone 1 b3 b5 1 b3 b5 b7
Compare the intervals in each of these chords to the 7th chord chart I gave you above. You will see that the I and IV are Maj7, the ii, iii and vi are min7, the V is Dom7, and the vii is min7b5 (half diminished). These are the most commonly used 7th chords. You need to know them very well, and you need to know where they sit within the chord scale.
Also, notice that the V chord (Dominant) is the only place that we find the intervals 1 3 5 b7. That is why that particular arrangement of intervals has been given the name Dominant 7.
Here is a common fingering for each of the possible 7th chords:
For each of these chords, you don't want to play the A-string or the high E-string. The high E-string is easy to leave out. You just have to make sure you don't hit it when you strum the chord. The A-srting is a little harder to leave out. What you have to do is dampen that string with the finger that is playing the low E-string. Do this by angling that finger so that it lightly touches the A-srting and keeps that string from ringing. This is easier to do than you may be thinking, so don't be shy. Give it a try.
Also, the correct fingering is given below each chord. Though some of the fingerings may seem a little awkward, I strongly recommend that you learn to finger the chords this way. How you finger a chord is very important when it comes to using the chord within a chord progression. These are the fingerings that have proven themselves every time.
Learn each of the various 7th chords in the diagrams above. Don't just memorize them. You gotta know this stuff inside and out. That includes knowing which note is functioning as which interval. practice switching back and forth between every possible combination of 7th chord. This will either tie your fingers in knots or increase your dexterity ten-fold.
Once you have the fingerings that I have shown you down cold, practice moving 7th chords through the chord scale like this:
If you can play through that without fumbling, you're doing pretty well.
Next, you need to start figuring out other possible fingerings for each of the 7th chords in all keys.
I strongly suggest that you get yourself a couple of good chord books. These are also called chord dictionaries. There are so many possible ways to play 7th chords (as well as extended and altered chords) that a person can easily get lost or overwhelmed. A good chord book will help you to cut through the confusion and learn the tried and true fingerings used by most players.
The two books that I personally recommend are:
Chord Chemistry by Ted Greene - This book is the most comprehensive chord reference I have ever seen. The author goes to the trouble of showing you every fingering imaginable for each chord. Lucky for us regular folks, he also breaks them into one section of essential fingerings and another section of "other fingerings". This book also covers how to use these chords in a thorough and logical manner, unlike most chord books I have seen.
A Guide to Chords, Scales & Arpeggios by Al Di Meola - This book is nowhere near as comprehensive as Chord Chemestry, but the manner in which the chords are organized will help you to learn the essential fingerings faster. There is also a section on scales and arpeggios and a section where Al provides excerpts from his own tunes to show you how to use and improvise over the chords you have learned.
These two books compliment each other perfectly, and will provide you with the resources you need to really learn your chords.
The next step is to plug these chords into a few standard chord progressions:
Formula Example ii V I Dm7 G7 CM7 I ii iii ii CM7 Dm7 Em7 Dm7 I ii iii ii V I CM7 Dm7 Em7 Dm7 G7 CM7 iii vi ii V I Em7 Am7 Dm7 G7 CM7 I IV ii vii I CM7 FM7 Dm7 Bm7b5 CM7
As you may have noticed from the examples, 7th chords are used most often in jazz music. But they also form the basis for blues music. The standard blues progression doesn't just follow the chord scale though. It utilizes a unique variation.
The standard blues progression is based off of the I, IV and V chords from the chord scale, but each chord is treated as a Dominant 7 chord. In the key of C, the progression looks like this:
C7 //// //// //// //// F7 C7 //// //// //// //// G7 F7 C7 G7 //// //// //// ////
If you've never seen this way of writing a chord progression, it's pretty basic. The slash marks represent strums of the guitar strings. Each group of four strums is equal to a measure or bar. There are 12 bars. You've probably heard people talk about playing a 12-bar blues. Now you get to find out what it means.
The basic formula for a 12-bar blues is 4 bars of the I chord (C7), 2 bars of the IV chord (F7) and then back to the I chord for 2 bars. This is followed by what is called the "turn-around" because the sequence of chords in the final four measures sets you up to play the whole thing over again. The turn-around consists of one bar for each for the the V chord (G7), IV chord, I chord and V chord in that order.
Now, you are not relegated to playing jazz or blues if you decide to whip out some 7th chords. A lot of rock, country and folk tunes throw in the occasional 7th chord to spice up a progression. The best thing you can do is grab some song books and look over the chord progressions. You can learn a lot that way.
Also, don't be afraid to experiment. I have used various 7th chords in a lot of stuff I have written, even some really heavy rock progressions.
You never know 'till you try.
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