Even if the company is on shaky legal ground, it probably will not lose its copyright, Brauneis said. It's cheaper for users of the song to pay royalties than to fight in court.
"I think there are substantial enough weaknesses in this copyright that a court more likely than not would find it not to be under copyright, that it is in fact in the public domain," Brauneis said.
"Yet it never gets into court because of the problems of mounting a challenge, And due to those problems we have people paying what amounts to $2 million a year or so into the coffers of Warner/Chappell," Brauneis said.
And so a simple six-note song will continue to be big business for years to come.