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Basic Harmony

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Chord Progressions

In a musical composition, a chord progression or harmonic progression (informally chord changes, used as a plural) is a succession of chords. Chord progressions are the foundation of harmony in Western musical tradition from the common practice era of Classical music to the 21st century. Chord progressions are the foundation of popular music styles (e.g., pop music, rock music), traditional music, as well as genres such as blues and jazz. In these genres, chord progressions are the defining feature on which melody and rhythm are built.

In tonal music, chord progressions have the function of either establishing or otherwise contradicting a tonality, the technical name for what is commonly understood as the "key" of a song or piece. Chord progressions, such as the extremely common chord progression I-V-VI-IV, are usually expressed by Roman numerals in Classical music theory. In many styles of popular and traditional music, chord progressions are expressed using the name and "quality" of the chords. For example, the previously mentioned chord progression, in the key of E^b major, would be written as E^b - B^b - Cm - A^b in a fake book or lead sheet. In the first chord, E^b major, the "E^b" indicates that the chord is built on the root note "E^b" and the word "major" indicates that a major chord is built on this "E^b" note.

In rock and blues, musicians might also often refer to chord progressions using Roman numerals, as this facilitates transposing a song to a new key. For example, rock and blues musicians often think of the 12-bar blues as consisting of I, IV, and V chords. Thus, a simple version of the 12-bar blues might be expressed as I-I-I-I, IV-IV-I-I, V-IV-I-I. By thinking of this blues progression in Roman numerals, a backup band or rhythm section could be instructed by a bandleader to play the chord progression in any key. For example, if the bandleader asked the band to play this chord progression in the key of B^b major, the chords would be:
 
B^b - B^b - B^b - B^b,
E^b - E^b - B^b - B^b,
F - E^b - B^b - B^b .

The complexity of a chord progression varies from genre to genre and over different historical periods. Some pop and rock songs from the 1980s to the 2010s have fairly simple chord progressions. Funk emphasizes the groove and rhythm as the key element, so entire funk songs may be based on one chord. Some jazz-funk songs are based on a two-, three-, or four-chord vamp. Some punk and hardcore punk songs use only a few chords. On the other hand, bebop jazz songs may have 32-bar song forms with one or two chord changes every bar.

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Chords In The Key

The chords in the major (Ionian) and minor (Aeolian) keys, the most popular scales, are the same. In each key there are three major triads, three minor triads and a single diminished triad.

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Major Key (Ionian)
C	Dm	Em	F	G	Am	B°
I	ii	iii	IV	V	vi	vii°
Minor Key (Aeolian)
Am	B°	C	Dm	Em	F	G
i	ii°	III	iv	v	VI	VII

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Number of Possibilities

If you're curious as to how many possible progressions there are using this finite set of seven, there is a way to determine this using finite mathematics. The diminished chord is not used very often, so for the sake of practicality, it will be removed from the list of chords to choose for the progression. In finite mathematics what is being sought here is what is known as a permutation. There are two types of permutations. One where repetition is allowed, and one where repetition is not allowed.
To find the possibilities of 4 chord progressions out of a set of 6 chords where repetition is allowed is: 6⁴ = 1,296 possible progressions.
To find the possibilities of 4 chord progressions out of a set of 6 chords where repetition is not allowed is: 6!/(6-4)! = 360 possible progressions

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Circle Of Fifths

In music theory, the circle of fifths is a way of organizing the 12 chromatic pitches as a sequence of perfect fifths. This arrangement can play an important role in developing chord progressions which makes it relevant to this subject.

The way it is constructed is like a clock. Starting on the note of C and moving up by fifths to each succeeding note a fifth away, the sequence will be C - G - D - A - E - B - F#/Gb - C#/Db - G#/Ab - D#/Eb - A#/Bb - F - C. The sequence is arranged in a circle like a clock:

The Circle & Key Signatures

This order places the most closely related key signatures adjacent to one another. From this illustration it can be seen that the two closest related keys to the key of C are the keys of F and G, both of which only differ from the key of C by one note.

Detailed Circles

Renderings of the circle can show much more relational data about keys, chords and modes. In this rendering, the relative minor keys are included along with the keys diminished seventh chord. It also illustrates how the modes are related to the key.

Looking at the illustration and all of the adjacent chords to the Tonic C, the Subdominant F is to the Tonic's left and the Dominant G is to its right. Above the Tonic C is the Submediant Am, C's relative minor. Adjacent to the Submediant Am is the Supertonic Dm to its left and the Mediant Em to its right. Above the Submediant Am is the Leading Tone B Diminished. This pattern repeats around the circle making it very easy to find all of the chords in each key. It can also be determined which chords are in the different modes. The mode headings on this circle relate specifically to the key of C Ionian also known as C Major.

To find all of the chords for C Dorian, look at the Dorian heading and all of the chords below. From this it can be determined that the chords for C Dorian are:
Cm, Dm, E^b, F, Gm, A°, B^b

To find the chords for C Aeolian also known as C Minor, look at the Aeolian heading. It can be determined that the chords for C Aeolian are:
Cm, D°, E^b, Fm, Gm, A^b, B^b

This same process can be used to find the chords for all of the modes

Dominant Seventh Resolution

The following explanation uses the key of C and the Dominant Seventh chord G7 (G-B-D-F) to illustrate this concept. Notice that the leading note (B) and the subdominant note (F) combined form a diminished fifth also known as a Tritone. The clashing sounds produced by playing these two notes together gives the dominant seventh chord its dissonant quality (i.e, lack of harmony, or it's instability). The dominant seventh is perhaps the most important of the seventh chords. The V7 chord typically functions to drive the piece strongly toward a resolution to the tonic of the key. Because the circle of fifths is build upon fifths, which in the key is the dominant's interval, each chord in the circle, moving counterclockwise is the dominant to the next key or chord. Since the dominant seventh want to resolve to the tonic, a series of resolutions can be made in traveling to the tonic of the base key. This is covered later with Secondary Chords, specifically Secondary Dominants

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12 Bar Blues

The 12-bar blues (or blues changes) is one of the most prominent chord progressions in popular music. The blues progression has a distinctive form in lyrics, phrase, chord structure, and duration. In its basic form, it is predominantly based on the I, IV, and V chords of a key. Mastery of the blues and rhythm changes are "critical elements for building a jazz repertoire"

Choose A Key Key of C Key of C# Key of Db Key of D Key of Eb Key of E Key of F Key of F# Key of Gb Key of G Key of Ab Key of A Key of Bb Key of B

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Minor 12-Bar Blues

i7	i7	i7	i7
iv7	iv7	i7	i7
bVI7	V7	i7	i7

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Common Chord Progressions

There are many common chord progressions that are used over and over again.

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The 50s Progression

The '50s progression (also known as the "Heart and Soul" chords, the "Stand by Me" changes, the doo-wop progression and the "ice cream changes") is a chord progression and turnaround used in Western popular music. The progression, represented in Roman numeral analysis, is: I - vi - IV - V. For example, in C major: C - Am - F - G. As the name implies, it was common in the 1950s and early 1960s and is particularly associated with doo-wop. The first popular song to use the progression was Blue Moon, written in 1934. This inspired Heart and Soul in 1938.

Songs With The 50s Progression

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Variations of the 50s Progression

As with any other chord progression, there are many possible variations, for example turning the dominant or V into a V7, or repeated I - vi progression followed by a single IV - V progression. A very common variation is having ii substitute for the subdominant, IV, creating the progression I - vi - ii - V (a variant of the circle progression) and thus the ii - V - I turnaround.

Choose A Key Key of C Key of C# Key of Db Key of D Key of Eb Key of E Key of F Key of F# Key of Gb Key of G Key of Ab Key of A Key of Bb Key of B

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The I - V - vi - IV Progression

This is a very popular progression. Songs that use this progression include:

Inversions or Rotations of I - V - vi - IV

There are three other progressions from the I - V - vi - IV progression derived from rotating or inverting the progression. In other words, by starting on a chord other than the first chord the following are derived: V - vi - IV - I, vi - IV - I - V, IV - I - V - vi. The most popular of the rotations is the vi - IV - I - V. Songs that use this progression include:

Choose A Key Key of C Key of C# Key of Db Key of D Key of Eb Key of E Key of F Key of F# Key of Gb Key of G Key of Ab Key of A Key of Bb Key of B

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The I - V - ^bVII - IV Progression

I - V - ^bVII - IV may be viewed as a variation of I - V - vi - IV, replacing the submediant with the subtonic.

Choose A Key Key of C Key of C# Key of Db Key of D Key of Eb Key of E Key of F Key of F# Key of Gb Key of G Key of Ab Key of A Key of Bb Key of B

I

V

bVII

IV

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vi - ii - V - I (Circle Progression)

This progression is known as the Circle Progression and it can sometimes be seen as a rotation of the variant of the 50s progression, I - vi - ii - V. It is one of the most common chord progressions in jazz. The progression is often used as a turnaround, occurring as the last two bars of a chorus or section. The I - vi - ii - V chord progression occurs as a two-bar pattern in the A section of the rhythm changes, the progression based on George Gershwin's "I Got Rhythm".

Choose A Key Key of C Key of C# Key of Db Key of D Key of Eb Key of E Key of F Key of F# Key of Gb Key of G Key of Ab Key of A Key of Bb Key of B

vi

ii

V

I

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Bebop 12-Bar Blues

The following progression uses what are known as secondary chords. Secondary chords are a type of altered or borrowed chord, chords that are not part of the music piece's key. In the bebop blues progression the secondary chord V/iib9 is used twice.

Choose A Key Key of C Key of C# Key of Db Key of D Key of Eb Key of E Key of F Key of F# Key of Gb Key of G Key of Ab Key of A Key of Bb Key of B

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