Why is it that some musicians who are undeniably popular with the public can’t seem to get any airplay on radio? From Josh Groban to Harry Connick, Jr. to a young Norah Jones, artists are discovering that there is no longer much of a connection between album sales and inclusion on corporate radio playlists. Radio stations claim that most of their listeners don’t buy many albums, but some musicians blame Arbitron’s method of measuring radio ratings for the disconnect.