You got it backwards.

It was copyrighted a LONG time ago.

[link|http://en.wikipedia.org/wiki/Happy_Birthday_to_You|http://en.wikipedia....y_Birthday_to_You]

The lyrics were copyrighted in 1935, 11 years before Patty's death, and the ownership has swapped hands in multi-million dollar deals ever since; the copyright is currently owned by Time Warner (a subsidiary of which bought the rights in 1988) and is scheduled to expire in 2030. It thus follows that unauthorized public performances of the song are technically illegal. It is not completely certain who wrote the lyrics to "Happy Birthday to You."