A company that had been collecting royalties for use of the Happy Birthday song no longer has a valid copyright claim to the tune, a US court has ruled.

Warner Chappell acquired the copyright to the song in 1988, 53 years after it had originally been filed by Summy Co. But now a US judge has stated that the rights only apply to specific arrangements of the music, and not to the song itself.

The melody of the song, which is used to celebrate birthdays all over the world, was composed by two sisters, Mildred and Patty Hill, in Kentucky in 1893. Originally called Good Morning to All, the lyrics changed to become the celebratory birthday song.

A 1927 book unearthed by filmmakers disputing the origins to the Happy Birthday song has been called a "smoking gun" in the case. (Court filing from Wolf Haldenstein Adler Freeman & Herz LLP)

A claim against Warner Chappell’s rights to the song was made in 2013 by Rupa Marya and Robert Siegel, a pair of documentarians making a film about the history of the Happy Birthday song.

Warner Chappell had issued a bill of $1,500 (€1,344) for the rights to use the song in the feature, with the documentary makers arguing the song is in the public domain and should therefore be exempt of copyright fees.

Judge George King ruled that Summy Co’s acquisition of the song’s copyright applied only to the melody, and not to the lyrics.

"The Hill sisters gave Summy Co the rights to the melody, and the rights to piano arrangements based on the melody, but never any rights to the lyrics," he said.

The rights to the song were eventually purchased by Warner Chappell for $25m (€22.4m) when they bought a successor company to Summy in the 1980s.

Since then, Warner Chappell has managed to accrue as much as $2m (€1.8m) per year from royalty payments every times the Happy Birthday song was used in film and TV, advertising or in public performances.

"We are looking at the court's lengthy opinion and considering our options," a Warner Chappell spokesperson said, after the ruling was announced.