BBC Radio 2 has a Listen Again (podcast) documentary about pioneering Rock and Roll DJ Alan Freed. I was going to listen to just a few minutes and finish it later, but instead sat through the whole show in one sitting. I think it should be available until next week.
http://www.bbc.co.uk/iplayer/episode/b00pqb52/The_Inventor_of_Rock_and_Roll_The_Alan_Freed_Story/