The Guitar's Role
The role of the guitar in early blues music was to accompany singers.
A guitar was a cheap and readily available alternative to a piano. Some of the earliest Robert Johnson recordings featured only solo voice with guitar accompaniment. For live performances, the piano was the preferred accompaniment instrument because it was able to project much louder than the acoustic guitar. The solo instruments of the blues were harmonica, voice, saxophone, and, occasionally, trumpet and clarinet. Because of the volume problems inherent in the acoustic guitar, it never caught on as a strong solo instrument. But the popularity of guitar was immense and acoustic jams were frequent in the churches and halls of the Deep South.
The invention of the electric guitar changed the role of guitar forever. Finally, the guitar was capable of carrying a band as an accompanist and a suitably loud soloist. The blues now had a solo instrument and rhythm player all in one, and the popularity of the electric guitar and electric blues exploded. The electric guitar also gave birth to rock and roll.