Original: The Chicago blues is a form of blues music that developed in Chicago, Illinois by taking the basic acoustic guitar and harmonica-based Delta blues and adding electrically amplified guitar, amplified bass guitar, drums, piano, and sometimes saxophone, and making the harmonica louder with a microphone and an instrument amplifier.
Simplified: The Chicago blues is a form of blues music that developed in Chicago, Illinois by adding electrically amplified guitar, drums, piano, bass guitar and sometimes saxophone to Delta blues.