The “Happy Birthday” song was protected by copyright, and was owned by Warner Music Group until last year. Warner bought the song from the song creators’ heirs in 1998. Sisters Patty and Mildred Hill wrote the song in the late 19th century. Warner has policed the commercial use of this song, which is why you have not often seen the song in films or on television.
Singer, Joseph William, Bethany R. Berger, Nestor M. Davidson, and Eduardo M. PenÌalver. Property Law: Rules, Policies, and Practices. 6th ed. New York: Wolters Kluwer, 2017. 190. Print.