Learn to improvise. 2004-2005. Lesson 03: harmony in groups of three chords.

The harmony changes continuously, but remains for a while within an area of three chords, called a key. As the keys during a piece of music change, they are called temporary keys. This way you can distinguish them from the initial key, which is indicated at the beginning of a staff in staff notation.

This thinking in groups of 3 chords is very important and is common in the world of music, but seldom expressed in this simple way. I will call them the three main chords of a key. Their root notes are on the 1st, 4th and 5th notes of the scale (for C the scale has the white keys and the 3 root notes are c, f and g) and consequently the 3 chords are indicated by I, IV and V. I is called root, V is called the dominant chord and IV subdominant chord. The scale of a key consists of all the notes of the three main chords in a row (e.g. the main chords of the key of C are the chords C, F and G and all the notes of them in a row are the white keys c d e f g a b).

In practice the dominant chord is often played as seventh chord and then called dominant seventh chord. The reason this is possible is because the seventh note (the note two key steps left of the root note of a chord, e.g. G = g+b+d and G7 = g+b+d+f) belongs to the scale of C (the seventh note of G7 is f, which is also a white key). The seventh notes of I and IV does not belong to the scale, in other words does not belong to the key.

Changing from one key to another is called modulation and is an important moment in the harmonic stream. Take care you don't falter on that very moment! Those moments are treacherous, as they are more difficult than a stream within a key and moreover have a climax.
Initial G and a climax with temporary key Am.

In a chord scheme never is indicated where the modulations are. You have to feel yourself when a key changes and to which one. For improvising this must be known beforehand, because you have to know which notes belong to the scale and which notes not.

Actually this thinking and working in groups of three chords, so in keys, respectively in scales, is the basis of this course. That's why I advise to start making improvisations in only one initial key, say C, so with the chords C, F and G(7), in order to learn what a key means and what the effect is in a melody of notes which belong to the scale and of the other ones.

When you start working with chord schemes running through different keys, it is handy to write those keys on the right place in the scheme (by color, by brackets, in another kind of character or the like). After a while you recognize these modulations automatically if you always play with the same initial key. It is practical to consider tones not belonging to the scale as treacherous. E.g. In the scheme C D7 G7 the initial key is C and the scale is c d e f g a b. During D7 the key is modulated to G and the scale has become g a b c d e f#. At this moment note f does not belong to the temporary scale. It is tricky as it has belonged to the valid scale just a moment ago (when the key was C). So you are inclined to interpret it wrongly (out of tune).
1st example has note f# during D7, the 2nd example note f.

Actually it is more complicated, because the place of the key in the chord scheme also has influence on the other notes of the melody note. E.g. consider note e-flat in the previous example. During key C it has a jazzy effect, but keeps on having that in key G (during D7).
Note e-flat is jazzy in C but also in G (during D7).
We would expect the jazzy note in key G to be the note b-flat. Well, it has a jazzy effect but in a different way.
Note b-flat is jazzy too during D7 but in a different way than e-flat.
HOMEWORK: Improvise as in the homework of lessons 01 through 04 of the previous year. Transpose all the songs you use for improvisation to one initial key (C is easy to understand, G sometimes easier to grab). Don't play the first years in different initial keys.
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