Some Quick Basic Chord Theory.
As we discussed in previous blogs, chords are built stacking 3rd intervals.
A 3rd interval is a 3-letter distance.
From C to E is a 3rd (CDE = 123), from E to G is a 3rd (EFG).
These 3 notes (C E G) combined form a C chord.
This is called a triad.
If we stack another 3rd on top of G (123 from G =GAB), we get B. Now we have: C E G B.
This is called a “7th chord”.
7th chords are 4-note chords. They are called that because the outer 2 notes are a 7th interval. (Or in other words: “7 letters apart”)
(CDEFGAB: From C to B is a 7th.)
In this particular case: C E G B is a major 7th chord. (Cmaj7)
There are 4 different types of 7th chords in a major scale.
- maj7 chords
This chord type happens on I and IV
In the key of C: Cmaj7 and Fmaj7
- 7 chords
This chord type happens on V.
In the key of C: G7
- m7 chords
This chord type happens on II, III and VI.
In the key of C: Dm7, Em7 and Am7
- m7b5 chords
This chord type happens on VII.
In the key of C: Bm7b5
Chord Tones & Tensions
The root, 3rd, 5th and 7th are called “chord tones”
“Chord tones” fall below the octave: root – 3rd – 5th – 7th
That number system is called a formula. Formulas in music, are used to show the interval distances between notes that make up scales and chords.
In other words: a formula is a number sequence, in which every number signifies an interval distance in relationship to whatever 1 is.
For example: the formula of a minor pentatonic scale is 1 b3 4 5 b7.
That means that that particular scale consists of a root (starting note), a minor 3rd interval above the root, a 4th (above the root), a 5th (above the root) and a minor 7th interval (above the root).
The formulas for the above chords are:
maj7 = 1 3 5 7
7 = 1 3 5 b7
m7 = 1 b3 5 b7
m7b5 = 1 b3 b5 b7
When you stack a 3rd interval on top of the 7th your next note is the 9th.
A 9th is a whole step above the root/octave.
The notes added to a chord above the octave, 9th, 11th and 13th, are called “tensions”.
9th is the 2nd above the octave
11th is the 4th above the octave
13th is the 6th above the octave.
There is no tension 10th or 12th, because these are chord tones. (The 3rd and 5th)
Theoretical Rules About The Harmonic Tensions.
There is really only one rule about tensions: Tensions need to be a whole step above a chord tone in order to be a harmonic option to a given chord.
Tension 11 is not an option on a maj7 chord.
This is easier to see with an example.
Cmaj7 = C E G B
E is the 3rd.
Tension 11 on C would be the note F.
F as a tension added to a Cmaj7 chord, is not an option, because it is only a half step above the 3rd.
However, F would be an available tension on a Cm chord.
The notes in a Cm7 chord are: C Eb G Bb
F as a tension 11 is an available option on Cm, because F is a whole step above chord tone Eb.
Hence you can have a Cm11 chord, but you can not have a Cmaj11 chord.
Learn & Memorize The Harmonic Tensions.
- Imaj7 ———- 9, 13
- II-7 ————– 9, 11
- III-7 ————- 11
- IVmaj7 ———- 9, #11, 13
- V7 —————- b9, 9, #9, b5 (#11) , #5, b13, 13
- VI-7 ————– 9, 11
- VII-7b5 ———- 11, b13
Translating this to say the key of C major, the chords are:
- Cmaj9, Cmaj13 or Cmaj7(9,13)
- Dm9, Dm11, Dm7(9,11)
- Fmaj9, Fmaj7(#11), Fmaj13, Fmaj7(9,#11,13)
#11 is called that because the note B (the #11) is a whole step above A (the major 3rd in an F chord)
From the root F to the #11 B note is an augmented 4th interval.
- G9, G13, etc..
- Am9, Am11, Am7(9,11)
Since the 5th in Bm7b5 is flatted, a whole step above that 5th is a b13th. That b13 note on a Bm7b5 chord is G.
Now you only need to research the chord shapes for chords with tensions.
This new knowledge will greatly jazz up your guitar playing with much richer sounding chords.
Later on we’ll discuss tensions on subV7 or secondary dominants.
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