Simplify the following text for a Grade 7 native English-speaking person.
Original: Robert Johnson , born Robert Leroy Johnson ( May 8 , 1911 â `` August 16 , 1938 ) is one of the most famous Delta blues musicians .
Simplified: Robert Leroy Johnson ( May 8 , 1911 â `` August 16 , 1938 ) was an American blues singer and musician .