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The Key, the Scale and the Related Chords

Guitar Lesson by Kirk Lorange

If you are new to music, it would be best if you have a read of this first.

What is a Key? It's a term you will hear all the time when playing music, and it's a good idea to have some kind of mental picture of just what it is. The word 'key' is very appropriate, because knowing the key automatically unlocks a whole lot of information about a piece of music. There are 12 keys, one for each note, all the laid out in the same way. This lesson uses G. It's a good guitar key to demonstrate this lesson, as you will soon find out. 

The most basic element to a key is the major scale. Lets first listen to a G major scale that starts on the low G (fret 3 of the thickest string), going all the way up to the 15th fret of the thinnest string. It spans 3 octaves. Remember that the 7 scale notes are like days of the week ... they keep repeating into other weeks. In this analogy, a week = one octave.

Listen to a midi file of 3 octaves of the G scale

Familiar sound, isn't it? It's that Do Re Mi thing. This example goes up through the scale 3 times, 3 octaves. So it's like looking at 3 weeks worth of days, starting at Monday.

Lets now bring the guitar into the picture. As you know, one of the strings is tuned to G, the 3rd string. So that's where we'll start to play just one octave of G scale, and we'll play the whole scale on that one string, moving right up to the 12th fret. Here is the tab:


You can see the formula for major scales just by looking at the numbers. The formula is Tone Tone semitone, Tone Tone Tone semitone. Most of the notes are 2 frets apart, a couple are one fret apart. The blue letter show the formula. I've written the note names above the tab.

Listen to a midi file of this single G scale

Now, and this is going to take some thinking about if you're new to music, we're going to look at the next string up, the 2nd string. That string is a B string. You can see that B is in the G scale, so we're going to play the G scale starting and ending at B on that string ... we're sort of dropping into the G scale at the B note, and playing it up to the next B note ... like looking at one week starting at Wednesday. The pattern of tones and semitones will be jogged out, of course, but it will still be the G scale. Here is the tab:


If you look at the notes, you'll see they are the notes of the G scale, but starting and ending on B. 

Listen to a midi file of this G scale starting at B

Now we're going to look at the string below the G string, the D string. D is also in the G scale, so now let's play a G scale, starting at D on that D string. Once again, you have to really let it sink in that we're still playing the G scale, but starting and ending on the D note. Now we're starting our week at Friday, going to the next Friday. Here is the tab:


Do take the time to look at the note names and really understand that they are the same notes as the other two strings, but starting and ending on different notes. 

Listen to a midi file of this G scale starting at D

Here is where it gets interesting!! It just so happens that guitars are tuned in such a way that those three strings when played open ARE a G chord. The formula for chords is to take three alternate notes from a major scale and play them together. In the case of G, those 3 notes are G, B and D, which are those three open strings. it doesn't matter that the D note is lower than the G, it still is, always was and for ever will be a G chord.

Because the scale was kept intact on the other strings, now when we combine the notes from all three strings, we get 7 chords. Those chords are the related chords from the key of G. Here is the tab:


Here is what they look like on the fretboard, each chord has its own color.


Listen to a midi file of these related chords

Now they sound like a scale made up of chords. 

So here, using the fretboard itself as the graph paper, we have unraveled the mystery of scales, chords and keys. If you're familiar with chord shapes, you can see very plainly that there are three major chords , three minor chord and there's that 'dim' chord there ... diminished. It's really 'half-diminished' ... don't concern yourself too much with this loner for now.

These chords are represented by the Roman numerals I often refer to in the lessons. They're written:

I - ii - iii - IV - V - vi - vii The upper-case represent the majors, the lower-case the minors and the half diminished.

What is shown here in G happens in exactly the same way with the other 11 major scales/keys, but not quite so neatly.

To summarize

We took one scale, the G scale and tracked it on three strings. It so happens that on a guitar, the open strings actually ARE a G chord. It's only a 3 note chord (triad) but that's enough to make it a proper chord. We then merged the three next notes up each into a chord, then the next, and so on. Together, these notes and chords form the Key ... in this case the key of G.

You can see the different shapes for the major and minor chords. They're different because of the irregularity of the scale. The note that differs is the treble note which is the 3 of the chord. All of these triads are 5-1-3 triads, meaning that the root (1) is sandwiched between the 5 and the 3. So just by studying the tab, you can see that the only difference between major minor chords is the 3 ... minors have 'flat 3s'. 

You can, of course, add more 1-3-5s to the other three strings and flesh these triads out to bigger, six string barre chords, but this lesson is just to show you how the related chords come about.