# Guitar/Chord Progressions

A knowledge of chord progressions will help you communicate and play with other musicians. Knowing the most commonly used chord progressions allows for greater enjoyment and unity when playing with other musicians.

## The I-IV-V

The most common chord progression is I-IV-V. Note that Roman Numerals are used to describe these chord progressions, where the "I" chord stands for the chord on root note, the "II" for the chord on the second note of the scale, and so on. Many songs use only these three chords. If one views chords as a set of balancing scales with the root note and octave root at opposing ends it will be noted that the IV and V chords are at equal distance respectively to the root and octave root. Take for example the key of C major:
C - D - E - F - G - A - B - C
You will see that the G note (or chord) is a fifth above the root note. The note F is a fifth below the octave. This movement of a fifth is very pleasing to the human ear in its sense of balance and cohesion in relation to the root note. Another way to view chord progressions is that of a journey. In the sense that the root (or tonic) chord is the starting point and the octave root is at the end. All other points (chords) provide interest and variation with the fourth and the fifth chord occupying a special place on the journey due to them being half-way.
Many chord progressions start at the tonic (I), moves away to somewhere else, only to come back to the tonic. You can play this progression with major chords or you can substitute minor chords for the IV or V.

### Applying the I-IV-V

Eddie Cochran and Buddy Holly are two artists who have used this progression extensively. Note that this chord progression uses a V7 chord. A V7 chord is just a V chord with an extra note. It is so common a device that when learning a chord progression many guitarist will play it through a few times using I-IV-V (normal V chord with no extra note) and then will play the chord progression I-IV-V7 a few times before switching back to the normal I-IV-V.
* E major (I)
* A major (IV)
* B7 (V7)

## I-vi-IV-V

This progression is commonly referred to as the 50s progression, because it was common to many of the popular songs of the 1950s, notably "Stand by Me". Note that the vi chord is a tonic extension, as it contains many of the same notes as the tonic (I) chord. You may see this progression with sevenths added in a blues song (e.g., G7, e min 7, C7, D7). Here is the progression in the key of G major.
* G major (I)
* E minor (vi)
* C major (IV)
* D major (V)

## The I-V-I-I

This is a popular progression at the beginning of a much larger line, and can be combined with many other scale degrees.

## II-V-I

As its name indicates, the progression is: IImin7, V7 and Imaj7. In a pop song, the chords might be IImin, V7, IMaj, with the first and last chord being three-note chords (triads). In jazz, all three chords are usually seventh chords. The II/V/I is important in jazz, where some songs have the progression in a number of keys.
* Dm7 (ii-min7)
* G7 (V7)
* Cmaj7 (I)
Alternatively you can change the chord type on the II, and alter the voicing of the V. Some examples are:
* IIm7b5(9)/V7alt /Imaj7
(with a V7alt, the performer alters the 9th to b9 or #9 and/or makes the 11 into #11 and/or makes the 13 into b13)

### Applying the II-V-I

II-V-Is can be chained together, creating complex progressions. Here's an example that starts in C major and moves to the relative minor, a minor:
* C major (I)
* Bm7b5 (II)
* E7 (V)
* Am7 (I)
* Dm7 (II)
* G7 (V)
* Cmaj7 (I)
An example of complicated progression that can be created this way is the "Coltrane Changes", where the "I" chords move by Major 3rd intervals. Here's a simple example:
The way the ii-V-I progression works is first that it moves by 4ths upwards, which very often produces interesting results, and the 7th goes down a half tone below and becomes the following chord's 3rd.

## Minor ii-V-i

Another commonly used chord progression is the minor ii-V-i. One can derive this from the melodic minor scales shown above, while substituting a IminMaj7 for the IMaj7 chord, or by using three modes from one harmonic minor scale , which produces the following chord progression:
* ii m7 b5/ V7 / i
In the key of c minor, this would be:
* d m7 b5/ G 7 / c min