Chord Progressions - How Chords Fit Together to Form Keys:
Certain chords sound "right" together, and are grouped together to form "progressions". Just as there are rules and patterns that guide how notes fit together to form chords, there are interval patterns that determine how chords fit together to create musical compositions. Chords that go together are said to form a "key". Understanding how chords are grouped together is perhaps the most important element of music theory - it helps you recognize, categorize, and create on your instrument virtually every kind of sound you hear in music. If you want to be able to "play by ear", compose music, or improvise, then understanding and being able to play chord progressions is absolutely essential.
Chord progressions are labeled by Roman numerals. As with intervals, Roman numerals are defined by the notes of the major scale. In the key of C, for example, I (1) = C, II (2) = D, III (3) = E, IV (4) = F, etc. (the notes of the C major scale). Every chord progression in our musical system can be labeled as a succession of Roman numerals in a key:
- The root note (letter name) of the chord is determined by the scale number indicated as a Roman numeral (i.e., in C, I = C, II=D, III=E, etc.).
- The type of chord is indicate by the size of the roman numeral, along with all of other the notations found in standard chord symbols. Large roman numerals represent Major chords, small roman numerals represent minor chords.
In the key of C, for example, Imaj9 = Cmaj9, ii7 = D minor 7th,V7 = G dominant 7th, VIImin7(b5) = B half diminished, etc. - by the definitions above).
Below is a listing of all the common Roman numerals found in our music system, with examples in the keys of C, A, and Bb. They are grouped together into categories and arranged on the fretboard using the "caged" patterns:
"Diatonic" Chords: defined by the numbers I, ii, iii, IV, V (and/or V7), and vi (viim7(b5) is a valid diatonic chord, but not used commonly in rock/popular music. It is used often in jazz and classical music). Play through the chords below to see how they are positioned on the fretboard, and become aquainted with their basic "plain vanilla" type of sound. These chords are the harmonic basis for many types of music. The chords I, IV, and V, in particular, are found in just about every type of music, and an overwhelming majority of songs in mainstream music (most songs contain the I, IV, and V chords). Knowing how to play that three chord relationship (I IV V) on the fretboard will allow you to play literally thousands of songs by ear on the guitar!
I ii iii IV V(7) vi
C Dm Em F G(7) Am
A Bm C#m D E(7) F#m
Bb C D Eb F(7) G
A note about diatonic chords:
The diatonic chords above share a common relationship because they are created from the notes of a single major scale. If you take the notes of a major scale, for example, and combine those seven notes in all possible ways to create chords (all possible combinations of those 7 notes), you get the chords which are "diatonic" to that major scale. Take a look at the diatonic chords in the key of C:
The C major scale notes = C D E F G A B
Below are the notes contained in each one of the diatonic chords (I, ii, iii, IV, V7, and vi):
C major chord (I) = C E G
D minor chord (ii) = D F A
E minor chord (iii) = E G B
F major chord (IV) = F A C
G dominant 7th (V7) = G B D F
A minor chord (vi) = A C E
All of the notes in the diatonic chords come from the C major scale :)
"Secondary Dominant" Chords:
Secondary dominants" are dominant chords (i.e., 7th and other extended/altered dominant chords) built on the I, II, III, VI, and VII notes of the key. Each of these chords creates a characteristicly unexpected harmonic "twist" in its sound:
I7 II7 III7 VI7 VII7
C7 D7 E7 A7 B7
A7 B7 C#7 D7 G#7
Bb7 C7 D7 Eb7 7
"Borrowed" Chords: chords that are said to be "borrowed" from another key. These chords are used most often in rock. You would be hard pressed to find a rock tune that didn't contain at least one of these chords. Borrowed chords typically contain flats ("b") in their label. A bVII chord, for example, is a major chord (large roman numeral), on the note one fret below VII. bIII is one fret below III, etc...
bVII bIII bVI iv v
Bb Eb Ab Fm Gm
G Bb F Dm Em
Ab Db E Ebm Fm
"Blues" Chords: Blues tunes usually contain a I7 (one of the secondary dominants), V7 (one of the diatonic chords), and IV7. In the blues, the IV7 chord resolves differently than it does in other types of music (see the section below for more info about chord movement and resolution).
I7 IV7 V7
C: C7 F7 G7
A: A7 D7 E7
Bb/A#: Bb7 Eb7 F7
Certain chords tend to feel like they should move or "resolve" to other specific chords within a progression. For example, after a VII7 chord, you will almost always find a iii chord. Below is a list of all the most common tendency progressions. Knowing these guidelines is extremely useful when playing by ear, composing, and/or improvising, because they provide a way of knowing the most likely next chord in any sequence (without guesswork), and thus provide a furthur structured approach to learning and deciphering chord progressions. Be aware that the secondary dominant chords have the strongest tendency to move in the specified direction:
I -> ANY chord (most chord progressions START and END on I !)
V7 -> I
I7 -> IV
II7 -> V or V7
II7 -> V, V7, and sometimes IV
III7 -> vi or VI7, and sometimes IV
VI7 -> ii or II7
VII7 -> iii or III7
v -> I7
iv -> typically seen in IV -> iv -> I (i.e., preceded by IV, and resolving to I)
bVI -> bVII
bVII -> I, IV, bIII, or V(7)
Modulation is defined as the changing of key. Changing keys is often used to create harmonic variety within songs and compositions of all types. Starting a song with the chords I, IV, V7 in the key of G (G, C, and D7), then playing the same chords in the key of A (A, D, and E7) is called a modulation from G to A.
Below are a number of typical modulation patterns found in common use:
Direct: Moving directly from one key to another, without any specific transitional chords. The shift is abrubt, from one key to another. This type of modulation is common in popular music. Most often keys are modulated up by half or whole step to create a sense of heightened energy. A song may start in the key of C, and then modulate to D and then E at the end to create a dramatic finish.
Relative: C major and A minor contain the exact same notes. Remember, a minor key can be defined as a progression starting on the vi chord - A minor is the vi chord in the key of C major. It is common to start and end a progression on vi for one section of a tune, and then start and end a progression on I for another section of the tune. Although this is not a true modulation, it creates a sense of harmonic shift between the two modes. Another common move is between major keys with the relative minor-major (vi-I) root note relationship. If C major and A minor are relative major and minor keys, for example, C major and A major are relative major keys (they have the same roote notes, defined by the I-VI relationship). This type of shift is a true modulation between two totally different sets of chords.
Parallel: Progressions often move between major and minor keys with the same root note. A song may start in the key of C major, for example, and shift to the key of C minor. C minor is the same key as Eb major (where cm = vi, Eb = I), so there is a totally different set of chords used in this type of modulation (one in which C=I, and one in which Eb=I).
Pivot Chord: V7 chords are often used to move to new keys. Before playing the I of the new key, the V7 of the new key is played at the end of a progression in the starting key. For example, to switch from the key of C to the key of Ab, an Eb7 chord can be placed at the end of the C progression to make the change sound more natural. Remember, the V7 chord has the strongest tendency of any chord to move towards I (Eb7 = V7 in the key of Ab). Secondary dominant chords are often used to make this type of progression away from the starting key. III7, for example, often moves to vi (see the tendency guidelines given earlier). If you resolve the III7 to VI instead (not a chord in the starting key), it facilitates a shift in which VI can be treated as a new I (a "parallel major" modulation). In the key of C, such a progression would look like:
C -> E7 -> A -> C#7 -> F#m ...
starting key of C: I -> III7 -> VI
new key of A: I -> III7 -> F#m ...
ii -> V7 Progressions: Virually every tune in the jazz idiom contains "ii-V" progressions. These two chords are often played through quick successions of keys:
| Cm7 | F7 | Bb | Bb | Ebm7 | Ab7 | Db | Gm7 C7 | F |
| ii | V7 | I | I | ii | V7 | I | ii V7 | I |
| Bb: | | | | Db: | | | F: | |
iimin7(b5) -> V7(alt) Progressions: This is the minor version of the ii-V progression. It typically resolves to a minor chord (thought of here as i ("minor 1"), but can also be thought of as vi in the relative major). This progression contains a half diminshed chord (m7(b5)), followed by an altered dominant (often an extended chord, with a b9/#9 and/or a b5/#5) :
| Em7 | F#m7(-5) | B7(b9) | Em7 | Em7(-5) | A7(b9) | Dm7 |
| i | iim7(-5) | V7(alt) | i | iim7(-5) | V7(alt) | i |
| Em: | | | |Dm: | | |
Very often, chord progressions are added to and changed to make the harmony sound more interesting.
Chord Progression Examples:
Below is a list of common chord progressions to practice and to help train your ear. You will be hard pressed to find any harmonic composition from any time period and style that doesn't have as its basis chord progressions contained in these examples. Learn to recognize these sounds and play them on the guitar, and you will be able to play most types of music by ear! Be sure to notice the tendency progressions in many of the examples:
Diatonic: (notice the "plain Jane" character of the sound these chords produce)
Secondary Dominant: (notice the unexpected "harmonic twist" created by the secondary dominant chords)
Borrowed: (play these progressions with distortion, and notice how most rock songs contain these harmonic "moves")
"Minor" Chord Progressions: minor progressions have a darker sound because they start and end on a minor chord. The key to understanding minor chord progressions is that they typically start and end on the vi chord (said to be the "relative" minor of I), and often contain the III7 chord (note that the III7 -> vi progression is one of the common tendency progressions listed in the previous section). Minor chord progressions typically contain the diatonic and secondary dominant chords. The key is that they start and end on vi, rather than I:
Modulating Chord Progressions: (progressions which move through several keys)
Progressions Using Chord Substitutions: (In each example, the original chord progression is given, and then additional chords are added using the guidelines above)
For reference, below is a listing of all the roman numerals, with their respective note names in each key:
I II III IV V VI VII
i ii iii iv v vi vii
1 2 3 4 5 6 7
A B C# D E F# G#
Bb/A# C D Eb F G A