Susan,

The blues developed an an African American art form. It is difficult to categorize prior to the 1920's because there were no recording capabilities and no one was writing this down the way Bach was written down.

Many blues musicians were itinerant, but there seem to have been some styles that developed within a locality. Areas well-known for their blues are: the Missiissippi Delta area, Texas, the Piedmont area, and Florida (this is not an exhaustive list). The music was spread both by the itinerant musicians and the development of the Juke Box. The early recordings of blues were either by collectors like Lomax or by for profit companies servicing the Juke Boxes.

In the 30's and 40's, southern African Americans moved toward the factory towns of the north, primarily Chicago. There they were introduced to electric guitars and the Chicago blues were developed.

It is hard to categorize to a novice (as you present yourself), but I will give it a shot. The blues are primarily (but not exclusively) a guitar based music. Often the solo performer is trying to imitate the work of the bass guitar, the rhythm guitar, and the lead guitar all at once.

Delta blues is characterized by a strong persistant muffled bass beat. Frequent use of a slide and open tunings is also common. The guitar leads are independent of the bass and frequently feature a repetitive melodic figure with minor variations.

The other styles tend to utilize a rhythmic figure created using both the bass and treble strings of the guitar. The emphasis on improvisation continues throughout the song, and there maybe less repetition than in the Delta blues.

Many individual performers developed personal styles that are immediately identifiable to the practices ear. Mississippi John Hurt and Reverend Gary Davis come immediately to my mind.

Susan (and others) this is really off the top of my head. Others more learned than I may contradict this information with veracity.

Roger in Baltimore