Blues is a significant form of music. Most of the music that you hear today contains specific elements of blues in one form or the other. The influence of Blues music is quite evident in all the prevailing forms of popular music like Rock & Roll, Rap, Pop, Jazz or Country.
Afro Americans were the originators of Blues and started this music in the late 19th century in the plantations around Texas, Mississippi and Louisiana as these were the places where most African Americans used to live. Blues music at that time was a combination of work songs, field hollers, religious music, rag time and African music. The Blues music derived a major influence from the African music, as that had a steady and strong beat that was created using drums & some other instruments. This beat and the singing was a major part of the Blues music.
Field hollers and work songs also greatly influenced Blues music, as they were a sort of storytelling songs sung a particular tone. Similarly another musical factors that influenced Blues was Rag time. It influenced the Blues and introduced fast beats with piano. This way as soon as the Blues became popular, it started influencing the rock music in a certain manner.
Although Rock music did not adopt Blues completely, but certainly it borrowed few elements from Blues in order to thicken its music plot. Slowly and gradually every kind of music started to add certain elements of Blues in their own music type to enhance its effect.