Guitar Scales and Modulation

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Modulation   Modulation 2   Modulation 5  Cadence]

Cadence, modulation harmonic, melodic, major and minor scales

In the chapter leading to modulation, we covered Major Scale Cadences, harmonic and melodic minor scale construction. We need to continue developing the diatonic major and minor scale cadences.

Out of all the possible 7 note scales, the Diatonic has the greatest number of constant intervals and the most major and minor triads. The Diatonic Major scale has 3 major, 3 minor triads with only 1 tri-tone, diminished 5/ Augmented 4th. Count each of the minor and major chords in the key of C Major below. 

C, Dm, Em, F, G, Am, B diminished. 

The Am natural minor scale below shares the same chords and notes of C major. But notice that the 1, 4, 5 progression would consist of only minor chords. Another popular progression would be Am F and G .

Am,  B°, C , Dm,  Em, F and G

A harmonic minor

A, B, C, D, E, F and G# Notice by raising that G to a G# it creates the E major chord. By raising this note and changing the Em to E major will create the stronger cadence. Explaining this theory will be down the road.

The C major is the home note in the key of C major. You will write your song or progression around this chord. The popular major progressions and most famous are the 1-4-5 progression. Moving a 5th up and a 5th down will determine this progression. It has been determined that the 5th up would be the dominant major chord and note. And the 5th down would be the sub-dominant. Since this 5th chord is Major, it will produce a stronger cadence. If this G chord was the Gm chord the progression would be weakened. This is where the harmonic minor comes into play. One major difference between the harmonic minor and natural minor is the E chord. In the Am natural scale the E is minor, in A harmonic minor the E is a major chord. Since this E chord can produce a stronger cadence over the Em it will be found more in classical music.

We know now that there are seven modes to each major key. Out of these 7 modes, only two are capable or effective in creating harmonic music. For a scale to be effective, it must have a tonic triad. (Tonic triad, brings closure and completion). Out of the seven modes in the major key the Ionian and Aeolian modes can produce this tonic triad. However, the major progression will produce the stronger cadence. Don’t forget the Ionian and Aeolian modes are the 1st and 6th in every major key.

In the key of C major, these two chords would be the (I and vi) (C and Am). Recall the chords in the key of C major, C, Dm, Em, F, G, Am, B dim, C. In the key of C major, C would be the (I or Tonic triad) and in the Am scale, Am would be the (i or tonic triad).

The major scale is a powerful scale and can create a very powerful tonic function. The (I chord) is a powerful chord in the major key. When the (I – Tonic chord) is played in the root position not inverted, it will produce a very effective tonic or final function. Recall our inversion chapter, by playing the tonic chord in the 1st or 2nd inversion will weaken the cadence. 

For example, in the key of C major using the Am scale, the Am will do basically the same thing as far as being a tonic chord, but not as powerful or decisive as the C major scale. Since the Am or Aeolian mode has a less decisive cadence, it is usually not used in classical music. You may find the harmonic minors for  its strong tonic function. The Aeolian minor 5th weakens this cadence as compared to the Harmonic major 5th. This major chord will strengthen the progression.  

The Aeolian mode progression may want to drift back to the relative major scale, for this reason, care must be taken in chord changes, unless you want to switch back to its relative major. We will cover that subject down the road. As you play these modes you will begin to hear their medieval or ancient qualities. Before the 1600’s, music was written using modes.

Okay, what does this mean to me, you ask? To better understand what is going on, we need to start from the beginning.

A progression can consist of 3 triads or a progression using a 7th chord or the diminished chord in the major key. We will learn later the chords in the melodic and harmonic minor scales.  For now, we will be covering progressions using only diatonic major and minor triads of the scale. We will eventually get to the harmonic and melodic progressions.

Before we begin you must be up on roman numerals. From now our progressions will be illustrated using roman numerals. All major and minor keys will be illustrated the same way. Major chords get the Large Caps, and minor chords will get small caps. Look at the key of C major illustrated below.

Two examples below, but remember the roman numerals represent every major key in the same fashion. The key of C major and G major have been illustrated, but I could have used any key to do this.

I, ii, iii, IV, V, vi, vii° , in the key of C major these roman numerals represent:

C, Dm, Em, F, G, Am, B° in the key of C major

Or

G, Am, Bm, C, D, Em, F#° in the key of G major.

This means if I give you a (I, IV, V, I) progression in the key of C major, you would play the chords: C, F, G and C or G, C, D, G in the key of G major.

If we are working on the Am scale Am, B, C, Dm, Em, F and G this progression would be shown as: i, iv, v, i  or Am, Dm, Em, Am

The little circle (° ) is often used to represent the diminished chord.

It's time now to work on a few progressions in the key of C major and Am. The first progressions are those in the key of C major and using the C chord as the tonic or final chord.

Key of C major and progressions
Tonic   Supertonic Mediant Sub-Dominant Dominant Sub Mediant Leading Tone Tonic
C Dm Em F G Am B° C
I ii iii IV V vi vii octave
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