Copyright laws can be pretty confusing. That's why when one of the most famous songs in the world entered the public domain, no one knew about it. Filmmakers and entertainers were still paying hefty royalties to use "Happy Birthday" for years because Warner Chappell Music, who acquired the rights in 1988, insisted the copyright didn't expire until 2030. But in 2015, a federal judge declared the publishing company only held the rights to a specific piano arrangement of the 1893 song, not the music or lyrics. Warner Chappell agreed on a settlement of $14 million to compensate the thousands of people and entities who needlessly shelled out licensing fees for a free song.

The case left us wondering what other famous songs are free to use, and which are still tied down by copyright. See if you can discern the status of these songs.