November 23, 1936 was a good day for recorded music. Two men, an ocean apart, sat before a microphone and began to play. One was a cello prodigy who had performed for the Queen of Spain. The other played guitar and was a regular in the juke joints of the Mississippi Delta.

On that day 85 years ago, Pablo Casals and Robert Johnson both made recordings that would change music history.

This episode originally aired on NPR in 2011.