Diatonic Scale

The diatonic scale is another way to describe the major scale. For example, I could say that the chord G7 is diatonic to the C major scale, or that the chord A minor only contains notes diatonic to C major. Learn about this scale on the Music Theory page.

Chords

All chords can be placed into one of 3 categories - Major, Minor and Dominant. These basic types are colourless - this means that they are constructed of only the notes or intervals that are necessary to define them.

For example, a Major chord needs only the root (tonic) and the 3rd interval for it to be defined as a major chord, whereas the Minor chord needs the tonic (root) and the flattened (b) 3rd (a semitone below the 3rd interval). The Dominant chord is very similar to the Major chord with it's major 3rd, but it also needs the flattened (b) 7th interval (a semitone below the 7th interval from the major scale) to add the natural dominant tension - but what is dominant tension?

Dominant Tension

So, the Dominant chord contains a b7th Interval. This is why, compared to the Major chord, that it sounds a little 'tense'. This kind of tension is known as natural or diatonic tension, because the feeling of tension is created using a note from the major scale key centre.

For example, G7 is the Dominant chord in the key of C because it has the note F as it's 'tense' note. However, in relation to G (the root of G7), F is the b7 interval - in relation to C (from whence it came), it is the natural, or diatonic 4th interval.

Chord Harmony can be difficult to understand at the first attempt so don't be hard on yourself if you don't get it yet. Why not book your first guitar lesson and learn all about chords and harmony at the same time?

Cycle of 5ths

This illustrates logical chord progression and helps us understand what chords do and why they usually move in certain directions.

But what makes a chord progression logical?

It makes sense that tension should be released or resolved. So it is logical that the chord type containing tension (Dominant 7) should be resolved. The best way to release the tension in the Dominant chord is to change to it's natural key centre or tonic, or root.

This is the movement that drives the Cycle of 5ths round and round - in an ever spinning wheel.

For example, given that G is the 5th (interval) of the C major scale and G7 (Dominant) chord derives from the key of C - commonly known as the 5 (V) chord in the key of C, the most logical progression for the G7 chord is to resolve to C major - , better know as the one (I) chord.

So then we have the most common and recognisable sound in music - the V - I progression (5 - 1)

If we then convert the C major itself into a Dominant chord - C7, then by the same logic, it too has now become a little tense and should resolve to a new key centre/root/tonic.

A good musical example of how this cycle of 5ths is in a well written song is 'The Windmills of Your Mind' ,where the verse chords cycle around logically from B to E to A to D and resolve to G major.

Modes

Modes often confuse guitarists because they can be taught as separate scales. But in fact, each mode represents a sound or a flavour in the same way that a major chord have a different flavour from a minor chord.

Well, modes are extra flavours that are not produced by new chord types or new scales. They are produced when particular melodies are sung or played from a new key centre. In essence, if you want to play Dorian mode in D, you would play C major scale, but start from it's second interval, D. If you wanted to play Phrygian Mode, you'd start from the 3rd interval, E and resolve back to it.

So Modes represent sounds that your ear should learn to recognise, rather than a new set of scales to learn.