The 320-page score, presumed lost for nearly a century, was discovered in a Swiss cellar last September, and was due to be auctioned in December by Sotheby's in London, with an expected sale price of Ô£300,000-Ô£500,000, when the composer's grandson got an injunction to stop the sale.
Alexandre Rachmaninoff and three of the composer's great-grandchildren are bringing the claim to court. Their lawyer, James Ware, said, "Why shouldn't this manuscript belong to the relatives of Sergei Rachmaninoff? As far as they know, he never sold it or gave it away. How did it come to be in the possession of a private collector?"
According to the Telegraph, Sotheby's speculates that the manuscript was in fact given away, and the paper said it was likely that the auction house will claim it has the right to sell the work on behalf of the collector.
Sotheby's has declined to reveal the collector's identity.