Bosses at publishing firm Warner/Chappell Music Inc. have been collecting royalties for the tune's use since 1988, when they bought the rights from previous owners at Clayton F. Summy Co. for $15 million (£9.38 million).

However, the copyright claim was challenged in a 2013 lawsuit by producers at Good Morning To You Productions Corp., who are working on a documentary titled Happy Birthday.

Plaintiffs Rupa Marya and Robert Siegel argued the song should be "dedicated to public use and in the public domain" and on Tuesday (22Sep15), they emerged victorious.

U.S. District Judge George H. King declared the copyright, originally obtained by Clayton F. Summy, only covered specific piano arrangements of the tune and not the widely-recognised lyrics.

He stated Happy Birthday To You originated from an earlier children's song, Good Morning to All, which was written by Kentucky sisters Mildred and Patty Hill before 1893, but insisted, "The origins of the lyrics to Happy Birthday... are less clear."

The lawsuit seeks damages and restitution of more than $5 million (£3.13 million) to cover licensing fees publishers had collected from commercial users over the years. The judge has yet to decide on the damages portion of the case.

A statement released by Warner/Chappell chiefs following the groundbreaking ruling reads: "We are looking at the court's lengthy opinion and considering our options."