Blues is one of them. The origin of Blues is not clear. Spirituals were based on the story of God or Bible but Blues were based on wicked stories of the life of human beings. As if it's falling down from heaven to the ground.

W. C. Handy wrote down the first music sheet of "Memphis Blues" in 1909. There were no music sheets of Blues until then. Handy composed a famous "St. Luis Blues" in 1914.

The structure of Blues is based on 12 bars and its feature is that the 3rd tone and the 7th tone are flat called "Blue Note"

We are using a chromatic sign to flat half tone, but the ages of Handy there were different symbol for Blue Note. African musical scale is five tones scale. The seven scale of European music was strange for black people from Africa. So they created peculiar melodies in Blues.

In the early time, they sang E flat for E backing and B flat for B backing in C major songs. This method is called complete playing method of Blues.

A similar matter can be found in the old Japanese music such as Naga-uta of Ko-uta. Oh, there also exists "Blue Note" in Japan. They sing a major song in like minor feeling.