Every revolution begins with an idea, so we've created a countdown of The 55 Best Ideas in Music History. These are the decisions that altered the course of music, from Bob Dylan "plugging in" at the Newport Folk Festival to Adele deciding to write about her terrible taste in boyfriends. Hosted by Craig Marks and Rob Tannenbaum, authors of the best seller "I Want My MTV," this is a highly-curated retrospective.