The growing popularity of blues music coincided with changing attitudes within American culture after the Civil War. The music acted as a reflection of attitudes of the African American community during this period. It enabled individuals to express emotion and opinion without fear of being punished. Prejudices, racism and poverty were topics that were sang about in this emotional and expressive style of music. The migration north of many African Americans at the beginning of the 20th century, in search of a less oppressive lifestyles enabled blues to reach a wider audience. Blues became extremely popular in U.S. cities such as New York and Detroit.
Blues are well-know for their distinctive emotional and expressive style. Blues is also characterized by standard chord progressions, and the most common is the 12 bar blues. This style is made up of 12 bars of music in a 4/4 time signature and consists of usually three different chords. Eight bar blues and 16 bar blues are also common. Blues music is also characterized by the flattening of notes by a semitone or less. This is done for expressive purposes.
Jazz is a music style that was heavily influenced by blues music. It was popular in African American communities at the start of the 20th century and also incorporated European and African music traditions. The jazz style's most obvious link to blues is the flattening of notes to create an emotive sound.
Rock and roll is another music style that was heavily influenced by blues and jazz music at the start of the 20th century. However, rock and roll wasn't distinguished as another genre until the middle of the 20th century. Rock and roll traditionally had a blue's style rhythm, but with accentuated percussion and back beat. The musical genre developed to influence lifestyles, fashion and attitudes of the era.