The earliest form of the blues dates back to the early 1860s and was associated with the American blacks. The development of the blues was influenced by black folk music such as work songs, spirituals, field hollers, ring-shouts and certain popular ballads.
The mood of the blues usually portrays a condition of depression or melancholy. The lyrics often depict sadness, sorrow, loneliness, depression, sexuality and protest. Since harmony was not a part of their culture, blacks either sang solo or in unison, and often without any musical accompaniment. Today we call that a cappella singing.
In 1863, President Lincoln issued the Emancipation Proclamation giving the slaves their freedom. Black children
could now go to school and get an education. Churches became plentiful in black communities. Being free, Negroes were now able to hear the music of the white man. They heard spirituals being sung
by white choirs in harmonization, applying simple chord progressions in four parts. Up to that time, the Negroes' only style of singing was in unison, that is, everyone singing the melody at the
same time.
Harmony, as was mentioned earlier, is of European influence. This form of harmonization was completely strange to the Negroes. African-American music had no harmony whatsoever. The Negroes however, with their keen ear for music were quick to adopt this European style and apply it to their own music.
The call-and-response routine was incorporated into a musical pattern. The first line of the lyric was repeated in the second line, with the same melodic phrase. The third line was sung with a different melodic phrase. Combining the three-line melodic phrases, this musical form fell into a twelve-bar pattern.
Although the Negroes had no accurate knowledge of music, their three-line stanzas established the rhythm-and-chord progression of the twelve bar blues. The chord progression of the blues involves three simple basic chords. They are; the tonic (I), the sub-dominant (IV) and the dominant (V). The distribution of these chords for the blues, are four bars of the tonic (I) chord, two bars of the sub-dominant (IV) chord, two bars of the tonic (I) chord, two bars of the dominant (v) chord and two bars of the tonic (I) chord.
One outstanding melodic feature of the blues is that of lowering the third and seventh degrees of the major scale. The lowered third and seventh degree notes are called "blue notes." These became essential in the development of early jazz. When jazz musicians came into the picture, they developed new forms and styles of jazz. Improvisation became the jazz musician's most important asset.
When the musician improvised around a given theme, additional notes and embellishments were included, which in turn created more harmonic progressions to the basic I - IV - V chords.