Chord in Blues
For the most part, the chords used in Blues are the same as those which evolved in European music beginning in the Renaissance. There are two chords which differ, and these are critical in identifying blues and in improvising Blues solos.
Given in the top row is the set of chords that evolved in European music and which are used in nearly all styles of American popular music. In understanding the symbols below each chord, there are several facts you must know. First, each chord is built on a note of the scale, in this case, the C major scale, and uses for it notes those found only in the scale. The lowest note in the chord in the chart is its root. The I maj7 chord is Cmaj7, the ii7 chord is Dm7, the iii7 chord is Em7, the IV maj7 is F maj7, the V chord is G7, the vi7 chord is Am7, and the vii half-dim7 is B half-diminished 7. Half-diminished 7 chords are often written in jazz charts as m7 flat 5, or minor 7 flat 5.
Each chord is numbered according to the note of the scale upon which it is built, the note which is also its root. The "I" chord is built upon the first note of the scale, the "ii" chord is built upon the second note, the iii chord on the third note, and so forth. The use of upper case identifies the chord quality. The upper case Roman numerals are major chords while those labeled in lower case are minor. There is an exception among the set, and that is the half-diminished chord found on the seventh note of the scale. It is not used often in major keys because it is in sound strongly similar to the V chord and hence will be addressed in a later article. A note the interval of a seventh is added to the chords in the chart. These 7ths are not present in many styles of popular music, but they appear on almost every chord in jazz and blues.
The chart has double duty. The reader can remove the 7th from the chord and what is left is the chord that would be used in styles in which 7ths are not prevalent. In Country, for example, the use of Cmaj7 would be unlikely for the tonic or I chord, but the user can remove the 7th to have a C major chord, and this chord would be correct to use in the style.
The 7ths also have quality, and here the symbols can get confusing. The "maj7" label attached to the I chord does not refer to the quality of the chord, which is major, but to the quality of the 7th. A major seventh or "maj7" is most easily reckoned not by counting the whole and half-steps between the root and the added seventh, which is the note stacked highest in the chord. Instead, it is far easier and far easier to count downward one half-step from the root and then add that note at the highest part of the chord. In the case of Cmaj7, the maj7 is B, located one-half step lower than the root C note but placed always as the highest note. The Cmaj7 is actually a major chord with a major 7th added to it.
The symbol "7" is actually an abbreviation. It indicates that a minor 7th is added to a chord. The easiest way to identify or locate the minor 7th is to count downward from the root one whole step then add that note in the highest position within the chord. In the case of the ii, iii, and vi chords, the chords are actually minor chords with minor 7ths.
The case of V7 is a second exception within the set of chords. After the tonic chord, it is the most critical in any key. This chord is called the "dominant 7 chord." It consists of a major chord with a minor 7th, and in terms of actual chord names, this is realized as a plain chord letter name and a plain "7." The numbers 9 and 13 are variant forms of the V7 chord and should be considered and treated in the same way. Just as it is not traditional to write "major" to indicate major chords, using just the letter name instead, we do not indicate that a 7th is minor by putting an "m" before the 7th in a chord symbol. Typical dominant 7 chords are written as C7, D7, E7, F7, G7, etc.
In traditional music, the dominant 7 chord controls harmonic and melodic direction. It contains the least stable notes in the scale. The root, 3rd, and 5th of the chord all pull to the tonic note for resolution. The 7th pulls downward to the 3rd of the tonic chord. In this key, the G (root), B (3rd), and D (5th) of the G7 chord all need to move to the tonic note C to resolve. The C note is the root of the C or tonic chord. The F note (7th) of the G7 chord moves downward to the next lower note in the scale to resolve, the E note, and the E note is also the 3rd of the C or tonic chord. The motion V7-I is the closing signature chord progression that identifies closure in Western music, and the appearance of these two chords marks the ending of nearly every piece of Western music since the early 16th century. There is only one "real dominant 7 chord in a key, and it is always found on the fifth note of the scale.
Blues differs from the European system in use in much of popular music in that it admits more scale notes than those found in the basic major scale. The additional notes are found in the minor pentatonic scale illustrated above. Many of the notes of the minor pentatonic scale and the major scale are shared (C, F, and G). Some notes found in the major scale are missing entirely from the minor pentatonic scale (D and A). What remains are two notes which are different from the notes of the major scale, and these notes are E flat, the flatted 3rd, and B flat, the flatted 7th. These two notes are the fundamental "blue notes" found in wide variety of American popular music styles. These notes are certainly the first blue notes and the minor pentatonic scale the first blues-based note sets that most young players learn.
These two notes have an effect on the basic chords used in Blues. The flatted 3rd of the minor pentatonic scale clashes terribly with the 7th of the IV maj7 chord. The flatted 7th of the minor pentatonic scale clashes terribly with the 7th of the I maj7 chord. The result is that in blues the two chords are altered to accommodate these blue notes. IV maj7 is altered to become IV7, a chord with the same note pattern as a dominant 7 chord but in the position on the fourth note of the scale, not the fifth. The I maj7 chord is altered to become I7, a chord with the same note pattern as a dominant 7 chord but on the first note of the scale.
Although these chords are "spelled" as dominant 7 chords, they do not function as dominant 7 chords, instead being simply altered chords that coincidentally resemble the dominant 7 chord. There is the suggestion, however, that I7 might imply or contain some of the function of the "real" dominant chord. In the simple blues progression below, notice that if the key were considered to be F and not C and all but the first two chords were ignored, the progression of C7 to F7 could be viewed or heard as V7-I in the key of F major.
||: I7 (C7) | IV7 (F7) | I7 (C7) | Iv 7 (F7) V7 (G7) :|| C7 ||
In listening to blues, there is a sense that music moves not just to a new chord but also to a new key whenever there is motion from I7 to IV7 or vice-verse, and it. This sense of shift is the result of the dominant-tonic relationship between the I and IV chords, and this is an element of the music that makes the music particularly potent. The relationship will be explored in greater depth in a subsequent article.
Those reader who are particularly observant have doubtless noticed that the flatted third of the minor pentatonic scale does not alter the third of the I chord. Here we have an aural phenomenon or tradition. The insertion at certain places in a melody of the flatted third, even over the I chord, does not create an unacceptable dissonant clash. In the evolution of American folk song, the flatted third of the minor pentatonic scale heard through the 19th century and earlier in black work song simply crept into the American style as an acceptable alternative, under certain circumstances, to the natural 3rd found in the major scale. The flatted third is traditionally introduced in popular melody late in the musical stanza, often over the last few chords before the stanza concludes. An example of the use of the flatted minor pentatonic third as an alternate note to the natural third of the major scale can be heard in "Froggy Went A Courtin'," a media file in a preceding lecture.
The chords in the graphic above appear here in the key of C major, but the chords, their qualities and the qualities of their added 7ths, and the Blues alterations described transpose literally to any major key since they remain the same regardless of the key, as long as the music is in major.
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