Chords are built from the notes of the scale or key. Scales and Key Signatures shows how the Major scale or Key Signature is built from the Chromatic scale with the W – W – H – W – W – W – H formula.
This set of notes is the basis for harmony and chord construction. Each note has a “Degree” 1st, 2nd, 3rd, etc. which we use to refer to the notes. These relationships hold no matter what the key.
- In every Major key, a 3rd is 4 half steps above the 1st degree. (3 half steps in minor keys)
- In every key, a 5th is 7 half steps above, or 5 half steps below the 1st degree.
The strongest combination of notes is the 1st and 5th played together. This two note chord is called a Power Chord.
Power Chord 1 - 5
Triads are chords built from three notes of the scale.
Major Triad 1 - 3 - 5 Minor Triad 1 - b3 - 5
Scales and Key Signatures shows how the Relative minor scale is defined as starting on the 6th degree of the major scale (aka Aeolian mode). Since scales repeat an octave higher and an octave lower, in practice it is sometimes easier to think about going down 3 half steps instead of going up 6 degrees.
As you can see,
- the 3rd of the Major Scale is 4 half steps from the root and is said to be a Major 3rd, and
- the 3rd of the minor Scale is 3 half steps from the root and is said to be a minor 3rd.
All chord formulas are expressed relative to the Major Scale. In terms of the Major Scale, a minor 3rd is a flatted Major 3rd, aka a flatted 3rd.
The order of the notes in a chord or harmony is not particularly important. No matter the order, a Major Triad is still a Major Triad. However, this “inversion” is sometimes notated as 1st or 2nd inversion.
Major Triad 1st inversion 3 - 5 - 1 Major Triad 2nd inversion 5 - 1 - 3
The shorthand notation for this is as a slash chord. For example:
- C/G is a C Major Chord, with G as the lowest note, which is the same as 2nd inversion.
If you pick every other note, 3 notes at a time from a Diatonic Scale, you end up with:
Roman numerals are frequently used to reference Triads built from 7 degrees of the scale. Upper Case roman numerals indicated Major Triads and use lower case roman numerals indicate minor Triads. The relationship holds for all keys.
- the I Triad is Major
- the ii Triad is minor
- the iii Triad is minor
- the IV Triad is Major
- the V Triad is Major
- the vi Triad is minor
- the vii Triad is diminished
This quickly tells us that the Triads that fall within the key, the ones that use only the notes of the key, follow the pattern.
I ii iii IV V vi vii° Key of C C Dm Em F G Am B° Key of G G Am Bm C D Em F° Key of D D Em Fm G A Bm C° Key of A A Bm Cm D E Fm G°
and so on…
This is also the basis for the Nashville Numbering System, which let’s songwriters write without specifying a key, and helps performers to transpose on the fly. Songs are frequently transposed for the range of the singer. Many chord progressions are expressed as I – IV – V or vi – ii – V – I, etc.
Augmented and Diminished
Augmented Triads raise the 5th.
Augmented Triad 1 - 3 - #5
Diminished Triads lower the 5th
Diminished Triad 1 - b3 - b5
Suspended Triads eliminate the 3rd degree.
Suspended  1 - 4 - 5 [Suspended] 2 1 - 2 - 5
Triads form the basis for 4 note chords.
Seventh chords come in several flavors
Major 7 1 - 3 - 5 - 7 Dominant [7th] 1 - 3 - 5 - b7 minor 7 1 - b3 - 5 - b7 minor half diminished 7 1 - b3 - b5 - b7 diminished 7 1 - b3 - b5 - bb7 Augmented 7 1 - 3 - #5 - 7 7 Suspended 4 1 - 4 - 5 - b7
9, 11 and 13 Chords
As we’ve seen, chords or harmony is built on every other note of a Diatonic scale. If we extend this into the next octave, we make use of the remaining three notes of the scale. Two adjacent scale degees played together sound very dissonant, but when separated an octave, sound more harmonious.
- the 9th is the 2nd degree in the next octave
- the 11th is the 4th degree in the next octave
- the 13th is the 6th degree in the next octave
9, 11 and 13 chords are typically built on 7 chords, but sometimes the 9th, 11th or 13th degree is added to a triad instead. The naming goes like this:
- a 9 chord is built on a 7 chord
- an 11 chord is built on a 9 chord
- a 13 chord is built on an 11 chord
C Major 9 1 - 3 - 5 - 7 - 9 C [dom] 11 1 - 3 - 5 - b7 - 9 - 11 Cm 13 1 - b3 - 5 - b7 - 9 - 11 - 13
A 9, 11, or 13 can be “added” to a triad or 7 chord, in which case it is marked as an Add9, Add11, or Add13.
C add13 1 - 3 - 5 - 13 or C - E - G - A Am add9 1 - b3 - 5 - 9 or A - C - E - B
Most people would probably stop here. The remainder is included for completeness. You may never run into any of these additional chords.
Some may be enharmonic with other chord names if another one of it’s degrees is considered to be the root, in which case an enharmonic name may be chosen for it’s context rather than it’s simplicity.
Major b5 1 - 3 - b5 quartal 1 - 4 - b7 quintal 1 - 5 - 9 Major 2 1 - 2 - 3 - 5 ( close voicing is more dissonant than add9 ) Major Add9 1 - 3 - 5 - 9 Major 6 1 - 3 - 5 - 6 minor 6 1 - b3 - 5 - 6 minor/Major 7 1 - b3 - 5 - 7 minor half diminished 7 1 - b3 - b5 - b7 ( minor 7 b5 ) dominant 7 b5 1 - 3 - b5 - b7 dominant 7 #5 1 - 3 - #5 - b7
Have I missed any?
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