An American film production company is suing the music publisher Warner/Chappel over the copyright to the most popularly sung song in the English language, Happy Birthday to You.
In March, Warner/Chappel charged the filmmakers NZ$1800 to use the song in a documentary.
The film company, Good Morning To You Productions, says the song, which is also known simply as Happy Birthday, belongs to the public and people should be free to use it.
Its class-action suit asks a New York court to order the music publisher to return the millions of dollars of licence fees it has collected for the song over the years.
The melody of Happy Birthday to You comes from the song Good Morning to All, which was written and composed by American sisters, Patty Hill, a kindergarten principal, and the pianist Mildred J Hill in Louisvillle, Kentucky, in 1893.