Simplify the following text for a Grade 3 native English-speaking person.
Original: One of the lengthiest documentaries of any medium ( 48 hours in the 1969 version , 52 hours for the 1978 version ) , The History of Rock & Roll is a definitive history of the Rock and Roll genre , stretching from the early 1950s to its day .
Simplified: The 1978 version was 52 hours long . The History of Rock & Roll told the story of Rock and Roll music from the early 1950s to its day .