A French court was set to rule Friday on whether "Bolero", one of the best-known classical music pieces in the world, was written by Maurice Ravel alone -- a decision with big financial stakes.
Ravel first performed "Bolero" at the Paris Opera in 1928 and it was an immediate sensation.
He died 10 years later and his heirs earned millions of dollars until the copyright ran out in 2016 and passed into public domain.
In France, copyright runs for 70 years after a composer's death, though some extra years were added to make up for losses during World War II.
However, the heirs of Alexandre Benois, a celebrated stage designer who worked on the original performance of "Bolero", say he should have been credited as a co-author all along and are demanding a share of the proceeds.
And because Benois died in 1960, that would put "Bolero" back under copyright until 2039.
"The music of the Bolero was created especially for the ballet" and should not be considered as a stand-alone piece of orchestra music, a lawyer for the Benois estate told a French court in February.
Ravel's estate supports the claim that it was a "collaborative work" with the Russian set-dresser, not least because they would start receiving copyright payments again.
The claimants point to various documents that name Benois as a co-author of the music.
On the other side is France's Society of Authors, Composers and Music Publishers (Sacem), which says the claim is based on a "historical fiction".
Sacem points to an official declaration signed by Ravel in 1929 identifying him as the sole author.
Having heard both sides, the court is set to make its decision on Friday.
Sacem's lawyer said the rights once generated "millions and millions of euros" per year, though this had fallen to an average of 135,507 euros annually between 2011 and 2016.
