Simplify the following text for a Grade 7 native English-speaking person.
Original: Rock and roll ( often written as rock & roll or rock 'n' roll ) is a genre of popular music that originated and evolved in the United States during the late 1940s and early 1950s , primarily from a combination of the blues , country music , jazz and gospel music .
Simplified: He is said to be the first person to use the expression `` rock and roll '' to describe rhythm and blues music . Alan Freed was one of the first to play rock and roll music on his radio show , and he organized the first rock and roll concert in Cleveland in 1952 .