What Key Is It In? - Learn Guitar Theory Part 4
Chords and key signatures. When learning a new song, especially if you want to improvise a guitar solo, one of the difficult things to figure out is what key is it in. Finding the key can be very tricky if you don't have any music theory knowledge. It's not possible to give a comprehensive overview of chords and key in a few easy to read pages. What we will do here is explain what "key" actually means.
When a piece of music is in a particular key it means all the chords are derived from the notes contained in one scale. For example, if a song is in the key of C major then all the chords used must contain notes from the C major scale. Likewise, if a piece of music is in the key of A minor, then the chords must be built from notes within the A minor scale.
Minor keys are a little trickier because there are three types of minor scale, the natural, harmonic and melodic minor scales. A cause of confusion can arise from minor keys because these three scale types are used interchangeably. In this case, if the chords are using notes from any three of those scales then it can be said to be in a minor key. Minor keys don't necessarily conform strictly to being just in the key of harmonic minor, or natural minor etc. More on that in the next part.
To figure out what chords belong to one set of notes in a scale, we use series of notes in third scale degrees, or every other note is an easier way of looking at it. Take the key of C major for example. We already know that C major chords are built using third scale degrees (every other note) of the C major scale. For a clearer picture, look at how the C major chords are built from the C major scale. The chord tones are the bold notes.
C major - C D E F G A B
C major 7 - C D E F G A B
C major 9 - C D E F G A B C D E F G A B
C major 11 - C D E F G A B C D E F G A B
If you have read the previous articles in this Learn Guitar Theory series then that should be making sense to you. Now, to find what other chords we can use, we do the same thing again, build in thirds, but starting from each note within the scale. So the next set of chords would be those starting from D, like so ...
C D E F G A B C D E F G A B = D minor
C D E F G A B C D E F G A B = D minor 7
C D E F G A B C D E F G A B = D minor 9
Etc..
Now you're probably wondering why D minor? This is where it can get a bit confusing, so bear with me. Because we are now starting from D, D is now also the root note for the notes that follow it. This means that to find out what the chord is, we have to work backwards, in effect, by comparing these notes to the D major scale. You might need to revise the section on chord construction if this isn't making sense.
What we have to do is find the notes for the D major scale and use the scale degree numbers to find what chord formula is appropriate for our new notes. Let's start with the first one in the above example.
C D E F G A B C D E F G A B = D minor
The notes are D F A. Now lets take a look at the D major scale.
D E F# G A B C# D E F# G A B C# D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
You'll notice here that the D major scale uses an F# but in our set of notes the F is natural. In this case it means that our F is therefore flat. So the notes D F and A will correspond to the scale degrees 1 b3 5. Looking back at the section on chord construction we can see that the formula 1 b3 5 is that used for a minor chord. Therefore the chord is D minor.
Now do the same thing again with the next example.
C D E F G A B C D E F G A B = D minor 7
The notes D F A C, with respect to the D major scale will produce the chord formula 1 b3 5 b7. Note it's a flat 7 because C should be sharp in the D major scale.
Okay, getting back to the key of C major. We'll just stick with the three note chords now to keep it short. Here are all of them.
C D E F G A B C D E F G A B = C major
C D E F G A B C D E F G A B = D minor
C D E F G A B C D E F G A B = E minor
C D E F G A B C D E F G A B = F major
C D E F G A B C D E F G A B = G major
C D E F G A B C D E F G A B = A minor
C D E F G A B C D E F G A B = B diminished
And for clarity, here are each of those major scales with the notes highlighted above and the corresponding chord formulas. We'll skip C and D as we've done those already.
E major scale - E F# G# A B C# D# ... E G B = 1 b3 5
F major scale - F G A Bb C D E ... FAC = 1 3 5
G major scale - G A B C D E F# ... G B D = 1 3 5
A major scale - A B C# D E F# G# ... A C E = 1 b3 5
B major scale - B C# D# E F# G# A# ... B D F = 1 b3 b5
Okay, that's the boring theory. The good news is that the chords themselves follow a pattern that makes things easy to remember. The observant among you may have noticed that the chords types follow this order.
Major - Minor - Minor - Major - Major - Minor - Diminished.
For three note chords (Triads), this order will always be the same in any major key. For four note chords, the sequence will look like this.
Maj7 - Min7 - Min7 - Maj7 - Dom7 - Min7 - min7B5
We can then carry on with five note chords that go like this.
Maj9 - Min9 - Min9 - Maj9 - Ninth - Min9 - half diminished 9th
It's unlikely you'll be using chords like half diminished ninth, or at least you don't need to know what they are unless you want to get more serious about music theory. Most of the time, if you see a chord like that then you can probably get away with just playing a half diminished (m7b5). If you do want to get better acquainted with music theory then I recommend a good book at the bottom of this page. So, where were we, ah yes, chords in key.
Figuring out what key a song is in, boils down to knowing the sequence of chords and matching them up to the major scale. Example, here are the notes for the D major scale. D E F# G A B C# Now using the chord sequence above we can see the chords in the key of D major are...
Dmaj - Emin - F#min - Gmaj - Amaj - Bmin - C#dim
And / or
Dmaj7 - Emin7 - F#min7 - Gmaj7 - A7 - Bmin7 - C#m7b5
And one more example in case you're still confused, lets look at the key G major.
G major scale - G A B C D E F#
Chords in the key of G
Gmaj - Amin - Bmin - Cmaj - Dmaj - Emin - F#dim
Gmaj7 - Amin7 - Bmin7 - Cmaj7 - D7 - Emin7 - F#m7b5
That covers the basics of finding major keys. Minor keys need a bit more explaining so we'll take a look at those next ... Minor keys explained.
Learn Music Theory The Easy Way
If you want to get a better understanding of music theory then I highly recommend these two books. I have found them to be among the easiest to follow but without lacking any information.
The Idiots guide to music composition compliments the theory book perfectly. It answers all the questions you expect to see in other theory books but never do. In fact, if you already have a reasonable understanding of music theory then you should check out the composition guide. Learning theory is one thing, how to use it is another. The Composition Guide plugs the gap between theory and it's actual use in music.
The Complete Idiots  
|
The Complete Idiots  
|
