The Jean Remy Library in Nantes, France has announced that a partial musical score in its holdings has been authenticated as coming from the hand of Wolfgang Amadeus Mozart. The single sheet, more than a third of which is missing, has been in the library for more than a century, but handwriting experts have only now concluded that Mozart wrote it (although the donor gave it to the library along with other Mozart letters). The fragment is believed to come from a Mass Mozart began composing but never completed.
Ulrich Leisinger, head of research at Salzburg's International Mozarteum Foundation, confirmed the document's authenticity, saying "His handwriting is absolutely clearly identifiable. There's no doubt that this is an original piece handwritten by Mozart." Only about 100 Mozart drafts are known, according to the AP report.
At the bottom of the page here, you can listen to a piano rendition of the fragment by Harvard's Robert Levin, although other musical scholars caution that playing the piece may not be so simple: "Musicians must work out the key signature and clef based on other clues in the music. The tempo is also mysterious. And there is no orchestration." Jean-Louis Jossic, deputy cultural director of the city of Nantes told the Guardian "If we gave it to four, five or six different musicians, we would have 10 different versions." Nonetheless, the library has commissioned a performance of the piece, to be held in January.