There was a legend that Johnson sold his soul to the Devil at the crossroads to become a great guitar player. According to Johnson himself, all that happened was that the Doctor gave him The Best of Robert Johnson for his birthday.
In 1931, the Eleventh Doctor took Alice Obiefune and, unwittingly, John Jones to see one of his live performances on the Dockery Plantation in Mississippi Delta. The Doctor described him as "one of the most electrifying live performers in the known universe".
However, when they arrived, Johnson and several other people were possessed by an alien force and attempted to attack the Doctor. The Doctor used his sonic screwdriver to reverse Johnson's trance and sent him back to the TARDIS with the sonic, promising that Alice would know what to do with it. Johnson aided Alice in her plan to cure the possessed mob by hooking his guitar up to the TARDIS and playing what he called a "TARDIS Blues" song.
The Eleventh Doctor described Johnson's voice as a fabulous falsetto.