TO QUALIFY: A song must have made the Billboard top 40 between 1960 & 2011 by at least two different acts. Each version of the song was assigned points based on chart performance, then points for each song were totaled to determine the rank shown. The biggest act for the song is listed first, followed by the other act or acts in descending order of success with the track. THE GLEE EXCEPTION: If one version of the song was responsible for 90% or more of all points, then the song was not included in the list. This was to largely eliminate most Glee Cast & American Idol covers that had a very short chart life.