Blues
Blues music has its origins among the freed black African slaves who worked on the cotton fields of North West Mississippi following the American Civil War. Influential in the United States Civil Rights Movement, Blues music has always been a hallmark of African American culture in the United States.
Origins
Blues Music was influenced in its inception by gospel, Scots-Irish ballads, field hollers, and rythmic dances called 'jump ups', which evolved into a system of music with a singer who would engage in call and response with his/her guitar. He would sing a line, and the guitar would answer. Blues influenced the development of most forms of popular music, including Rock and roll, Jazz, Hip-Hop, Rap and Country Music. Once hailed as being a foundation of modern music, blues has declined somewhat in the last few decades as other forms of music (primarily rock and roll) have taken its place.
African Influences
African Americans may have been the precursor to blues music. This was evident in the African field songs that they sung together as they worked. The loose rythmic style would have suited the African spirit more so than the almost rigid European Classical style of music prevalent amongst the cultured elite at the time. The common white man may have listened and played something more akin to what was known as Traditional music, prevalent especially in Irish American immigrant communities where the focus on the old homeland was strong, with instruments such as the Bódhran, Accordian, Tin whistle and Banjo shaping the development of country music throughout the United States.
The African American slaves, however, differed in their style of music. The emphasis was instead on something that would make somebody work in a happier environment. From this came the music that many White Americans considered the 'devils music' as it influenced movement of the body in ways unknown to traditional European based forms of music. This field hollering later evolved with fusions of traditional Irish folk and the quickly developing American country music into what we now know as Blues Music'.
12-bar blues
Much of moderm music is built around 12-bar blues, which plays the root, fourth and fifth chords of the particular key the song is played in. There are any number of variations, but three of the most popular are shown below. Straight 12-bar blues, in the key of G, would have this pattern of chords played and this pattern would be repeated throughout the song. This pattern is suited to eight note bass walks whenever one chord is played for two bars.
Straight 12-bar blues pattern
| G | G | G | G |
| C | C | G | G |
| D | C | G | D |
Instead of staying on the root chord (G) for so many bars, blues song often use the "quick turn-around" variation, which jumps to the fourth chord (C) on the second bar and right back to the root on the third bar of music.
"Quick turn-around" 12-bar blues pattern
| G | C | G | G |
| C | C | G | G |
| D | C | G | D |
By ending on the firth chord (D), this pattern leaves a sense of "tension" at the end of pattern. This tension can be relieved by ending on the root chord, like this.
12-bar blues resolving on the root
| G | C | G | G |
| C | C | G | G |
| D | D | C | G |