It goes like this: In 1893, a couple of lines of music were published in a book. The piece of music is eight bars long, and consists of a single-note melody which can be hummed in its entirety in about six seconds.
In 1927, this song was published in a separate compilation of similar musical pieces, with different lyrics which are known to have been informally attached to it for some time.
And now, as a result, if you want to reproduce the song Happy Birthday in any kind of media, you need to pay the Warner/Chappell Music Group for the right to do so, or risk being sued.
They collect millions of dollars every year this way. By claiming some bizarre kind of “ownership” of a universally familiar melody composed well over a century ago by some person or persons entirely unconnected with the people now profiting from it.
I’m trying to imagine a basically worse person than someone who’d demand money from someone else for the right to sing Happy Birthday. If you can think of anything more viscerally contemptible, let me know.