In a new article Copyright and the World’s Most Popular Song, Robert Brauneis of George Washington University persuasively argues that “Happy Birthday to You” is no longer in copyright due to deficiencies in authorship claims, registration renewals and improper notice upon publication:

The claim that “Happy Birthday to You” is still under copyright has three principal weaknesses. Most significantly, there is a good argument that copyright in the song has never been renewed. Under applicable law, the original term of copyright in the song ended in 1963. If no renewal application was timely filed, the song would have entered the public domain at that time. The only renewals filed were for particular arrangements of the song – piano accompaniments and additional lyrics that are not in common use. It is unlikely that these renewals suffice to preserve copyright in the song itself.

Second, the first authorized publication of “Happy Birthday to You,” in 1935, bore a copyright notice that was almost certainly not in the name of the owner of copyright in the song. Under the law in force at the time, publication with notice under the wrong name resulted in forfeiture of copyright protection.

Third, the current putative owner of copyright in “Happy Birthday to You,” the Summy-Birchard Company (a wholly owned subsidiary of Warner/Chappell Music, Inc.), can only claim ownership if it can trace its title back to the author or authors of the song. Yet it appears that the only possible authors to whom it can trace title are Mildred and Patty Hill themselves, and there is scant evidence that either of them wrote the song.

The best part the article though is the practical perspective on one of the major problems with copyright – orphan works:

copyright law needs a doctrine like adverse possession to clear title and protect expectations generated when, as with this song, putative owners do not challenge distribution of unauthorized copies for more than 20 years.