The traditional Happy Birthday tune is at the centre of a new copyright battle.

The ditty, titled Happy Birthday to You, is based on the track Good Morning to All, which was written in 1893 by American sisters Patty and Mildred J. Hill, but a copyright claim registered in 1935 credits authors Preston Ware Orem and Mrs. R.R. Forman with its creation.

Executives at Warner/Chappell Music obtained the copyright credits in 1990, and have been demanding payment for every use of the song on stage, Tv or in film ever since, insisting its ownership of the track in the U.S. does not expire until 2030, as works published after 1923 are protected for 95 years.

However, a class action suit filed in New York's Manhattan Federal Court is now challenging that assertion, with the plaintiffs - producers behind a new documentary about the song - insisting the tune originated in the 1890s and is therefore no longer under the record label's copyright.

The producers from Good Morning To You Productions Corp. had paid $1,500 (£968) in March (13) to license Happy Birthday to You for use in their film, but are now attempting to get their money back, insisting the song is in the public domain.