The melody and lyrics to the "Happy Birthday to You" song were written in 1924 by sister Mildred J. Hill and Patty Smith Hill. The sister filed a lawsuit in 1934 for unauthorized use of the song. Since 1935, the melody and lyrics have been protected by copyright. It is estimated that the "Happy Birthday to You" song brings in $2 million in royalties every year.
. http://musiced.about.com/od/historyofmusic/a/happybirthday.htm
