This might not be a known fact but the "Happy Birthday To You" song is copy-righted and who ever wishes to use it must pay royalty to Warner Music, the song maid more than $2 million dollars in one year in 2008.
Although we might do know it's original tune and lyrics back-bone was composed by the Hill sisters in the 1890s that had never been proven legally. It was copy-righted in 1935 by two compositors working for a company that was bought by Warner eventually absorbing the rights.
Well a few weeks ago! a college librarian in Kentucky found the long lost original manuscript about the song dated in 1883 under the name of none other than "Mildred Hill" and its original title "Good Morning To You"
This means the song can be associated to Miss Hill as the copy-right owner by composition and before history and since she already passed bless her soul the right automatically would become public for anyone to use without paying a cent to Warner Music.