Music Theory – Part 2
September 7, 2008 by Lee
Chords in the key
To stay in one key means that any chords used must contain notes from the same Major scale. Again using C Major as the example and staying with the rule that chords are built on third scale degrees, let’s see what happens if we do the same thing but start from the second scale degree instead of the first..
C D E F G A B
1 2 3 4 5 6 7
We now have the notes D, F and A.
D is the starting note here so if we compare that to a D major scale we can figure out from using the previous formulas that this is a D minor chord i.e..
D major scale contains the notes D, E, F#, G. A, B, C#.
Using the formula 1-3-5 we can see that a D Major chord consists of D – F# – A
Therefore D-F-A would translate the same as a 1-b3-5 making it a D minor.
Using this idea we can do the same thing again but starting on the third scale degree to find an E type chord, the 4th scale degree to get an F type chord and so on.
What we end up with is all these chords that belong to the key of C Major..
- C Major
- D minor
- E minor
- F Major
- G Major
- A minor
- B diminished
C E G = 1-3-5 taken from the C Major scale notes C-D-E-F-G-A-B-C
D F A = 1-b3-5 taken from the D Major scale notes D-E-F#-G-A-B-C#
E G B = 1-b3-5 taken from the E Major scale notes E-F#-G#-A-B-C#-D#
F A C = 1-3-5 taken from the F Major scale notes F-G-A-Bb-C-D-E
G B D = 1-3-5 taken from the G Major scale notes G-A-B-C-D-E-F#
A C E = 1-b3-5 taken from the A Major scale notes A-B-C#-D-E-F#-G#
B D F = 1-b3-b5 taken from the B Major scale notes B-C#-D#-E-F#-G#-A#
Diminished chords we have not spoke about and I’m not going to give any details other than the formulas that make the chords. There are actually three types of diminished chords..
- Diminished = 1-b3-b5
- Half diminished (also called minor7 flat 5) = 1-b3-b5-b7
- Full diminished or diminished seventh = 1-b3-b5-bb7
Yes you read that correctly, diminished seventh chord has a double flat 7. This actually makes it become the same note as the 6th in the scale however for theoretical reasons it’s true term would be a flat flat 7.
We can also extend these chords to go beyond Triads, I’ll use the G chord as an example but the same idea applies to all the others.
G B D F= 1-3-5-b7 taken from the G Major scale notes G-A-B-C-D-E-F#
G B D F A = 1-3-5-b7-9 taken from the G Major scale notes G-A-B-C-D-E-F#-G-A
Chord construction and chords relating to a key are important things to understand but the good news is it’s all fairly easy to remember.
For the formula of the most common chords it doesn’t take long to realise that..
- Major Triads, Maj7, Maj9 chords etc.. consist of scale notes stacked in third scale degrees
- Dominant chords consist of Major chord notes but with a flat 7
- Minor chords consist of Major chord notes but with a flat 3 and flat 7
Note: minor chords larger than 3 note triads are usually of the dominant type because they have a flat 7. There is also such a thing as a minMaj7 chord which will have a flat 3 but the 7 isn’t flat. i.e.. CminMaj7.. 1-b3-5-7 (C – Eb – G – B)
The Chord Numbering System
Just as we used numbers to relate note position in the Major scale we also do the same thing with chords that relate to each position of a Major scale, the only difference is when we write it down we use Roman Numerals instead of decimal numbers.
As in the previous section, starting from the first note of a Major scale the first chord will be Major, the second chord will be minor and so on. There are seven notes in the Major scale and so we obviously have seven chords associated with each note. Each of these chords can be of the Triad or extended type. The full sequence of chords is easy to remember..
Major, minor, minor, Major, Major, minor, diminished.
Maj7, Min7, Min7, Maj7, Dom7, Min7, Min7b5
The chart below shows how they are related to their corresponding scale position and the equivalent Roman Numerals
Note: It’s common practice to always use lower case numerals for minor chords and upper case for major.
You have probably heard terms like, “two five one in C” or “one four five in G” etc.. These numbers refer to the chords relation to the scale position.In the key of C, the chords are…
- I – C Major
- ii – D minor
- iii – E minor
- IV – F Major
- V – G Major
- vi – A minor
- vii – B diminished
A I-IV-V (one four five) in C therefore consists of the chords …
- C Major (I)
- F Major (IV)
- G Major (V)
These chords can be extended to CMaj7 – FMaj7 – G7
Here are some more examples..
- ii-V-I in C…….. Dmin7 – G7 – CMaj7.
- I-vi-IV-V in G…. GMaj – Emin – CMaj – DMaj
- I-IV-V in A…….. AMaj – DMaj – EMaj
The 6th chord in any Major scale sequence is called the relative minor. This would be Am in the key of C, Em in the key of G, F#m in the key of A and so on. We won’t discuss this further here other than to mention that the Key chord and the Relative minor chord share two of the same notes and have a reasonably similar sound, i.e.. C (C-E-G) Am (A-C-E).
Also the notes in the scale of C Major are the same notes found in the Natural minor scale starting on the 6th note. i.e..
- C Major scale C-D-E-F-G-A-B
- A Natural minor scale A-B-C-D-E-F-G
You hear a lot about the relative major and minor. Personally I would recommend not thinking too much about it. It’s common for guitarists to use this major/minor relationship as a handy short cut, for instance, move a minor scale pattern down by three frets and it becomes a major scale for the same key and vice versa.
While this is a handy trick it unfortunately does nothing to help you advance as a guitarist, in fact it does the exact opposite. My advice is to just know that every major scale has a relative minor and vice versa that share exactly the same notes, try to memorise these relative notes for every key and leave it at that unless you decide to get into more advanced music theory.
That pretty much covers the crash course on music theory, as mentioned already there is a lot left out of this but we have covered the important basics, the main stuff that there’s just no point not knowing!.