20 years ago, I chose for my dissertation texts written from 1920 through 1950, expecting them to come out of copyright one after the other during my career as a professor, but the Copyright Term Extension Act of 1998 added 20 years. Disney has made dozens of movies based on characters that are in the common domain, but lobbied for a law to protect its own property. The story of “Happy Birthday” offers some hope.

Now, the documentary film company says it has “irrefutable documentary evidence, some dating back to 1893, [which] shows that the copyright to ‘Happy Birthday,’ if there ever was a valid copyright to any part of the song, expired no later than 1921 and that if defendant Warner/Chappell owns any rights to ‘Happy Birthday,’ those rights are limited to the extremely narrow right to reproduce and distribute specific piano arrangements for the song published in 1935.” —Billboard.