Popular music has always reflected the feelings of the common people and their times, whatever period they lived in. In the present day, the problems we encounter are very different from those suffered by the descendents of the Negro slaves in the Mississippi Delta, for example. It's generally acknowledged that the Delta was the crucible that formed the original blues music, spawning such blues men as Son House, Leadbelly and the legendary Robert Johnson.
Even before guitars were widely used to create basic songs, workers in the Deep South would sing 'field hollers', a type of song without music that used a strong rhythm to help the associated work, which was often very repetitive, such as digging, cutting or chopping. Old films of Gandy Dancers exist that show this perfectly. Gandy Dancers were workers who moved along the railroad aligning the rails using long steel crow bars. A team of men would all push at the same time to maximize their force and the song provided the exact timing for this kind of work.
Although a typical blues song followed the 12 or 8 bar format, very often in the key of E or A, another form of the blues appeared that expressed the spiritual aspects of people's lives, and the Spiritual style of roots music was born. Typically, such a song took the form of call and repsonse, where the singer would either be answered by other singers, or by his guitar in later years. The road to modern blues music is paved with many different styles from various guiarists from almost every state in America, acoustic blues guitar lessons should relect this diverse spread.
In the 1930s it was common to have swing bands playing in noisy clubs or juke joints, often with a horn section and piano. The acoustic sound of a wooden guitar was becoming overcome by the other instruments, so the all metal construction of the National Steel type of guitar was favored. Very soon, more power was needed and the first electric guitar appeared. Although certain blues artists such as Big Bill Broonzy were very active in creating a new exciting way of playing, newcomers like Muddy Waters quickly saw the huge possibilities in playing a more amplified sound, with the extra tone effects that electronics brought to the overall sound.
It could be said that this was the time that rock and roll was born, when the new blues men adapted the old style traditional music that had it's roots in the African tradition and generated a new exciting sound that still contained all the power of the traditonal music.