NEW YORK (AP) — The moody waltz was carefully composed on a sheet of music about the size of an index card. The brief, moody number also had an intriguing name, written across the top in cursive: “Chopin.”

A previously unknown musical work written by European master Frédéric Chopin appears to have been found at the Morgan Library & Museum in Manhattan.

The untitled and unsigned work is on display this month at the lavishly appointed institution, which was once the private library of financier JP Morgan.

Robinson McClellan, the museum curator who discovered the manuscript, said it was the first new work associated with the Romantic-era composer discovered in nearly a century.

But McClellan concedes that we may never know whether it is an original work by Chopin or simply one written in his hand.

The piece, set in the key of A minor, is notable for its “very stormy, moody opening section” before transitioning into a melancholy melody more characteristic of Chopin, McClellan said.

“It’s his style. This is its essence,” he said during a recent visit to the museum. “It really looks like him.”

McClellan said he discovered the work in May while looking through a collection of the late Arthur Satz, former president of the New York School of Interior Design. Satz had acquired it from A. Sherrill Whiton Jr., an avid autograph collector who had served as the school’s principal.

McClellan then worked with experts to verify its authenticity.

The paper turned out to be consistent with what Chopin preferred for manuscripts, and the ink matched a type of ink typical of the early 19th century, when Chopin lived, according to the museum. But a handwritten analysis revealed that the name “Chopin” written at the top of the sheet had been written by someone else.

Born in Poland, Chopin was considered a musical genius from an early age. He lived in Warsaw and Vienna before settling in Paris, where he died in 1849 at the age of 39, probably of tuberculosis.

He is buried among a pantheon of artists at the famous Père Lachaise cemetery, but his heart, marinated in a pot of alcohol, is preserved in a Warsaw church, in accordance with his deathbed wish that the organ return in his native country.

Artur Szklener, director of the Fryderyk Chopin Institute in Warsaw, the Polish capital where the composer grew up, agreed that the document matched the types of ink and paper Chopin used during his early years in Paris.

Musically, the piece evokes the “brilliant style” that made Chopin a luminary of his time, but it also exhibits characteristics unusual for his compositions, Szklener said.

“First of all, it is not a complete work, but rather a certain musical gesture, a theme mixed with quite simple piano tricks hinting at a virtuoso style,” Szklener explained in a lengthy statement released after the document was revealed last month.

He and other experts speculate that the piece could have been a work in progress. It could also be a copy of someone else’s work, or even co-writing with someone else, perhaps a student for a musical exercise.

Jeffrey Kallberg, a music professor at the University of Pennsylvania and a Chopin expert who helped authenticate the document, called the piece a “little gem” that Chopin probably wanted to give to a friend or wealthy acquaintance.

“Many of the pieces he gave as gifts were short – sort of like ‘appetizers’ to a full-fledged work,” Kallberg said in an email. “And we don’t know for sure if he intended for the piece to see the light of day because he often wrote the same waltz more than once as a gift.”

David Ludwig, dean of the music faculty at the Juilliard School, a performing arts conservatory in Manhattan, acknowledged that the piece exhibits many characteristics of the composer’s style.

“It has the Chopin character of something very lyrical and there is also a bit of darkness,” said Ludwig, who was not involved in authenticating the document.

But Ludwig noted that, if authentic, the tightly composed score would be one of Chopin’s shortest pieces known. The waltz lasts less than a minute when played on the piano, as many of Chopin’s works predicted.

“In terms of authenticity, in some ways it doesn’t matter because it stimulates our imagination,” Ludwig said. “A discovery like this highlights the fact that classical music is a living art form.”

Chopin’s revelation comes after the municipal libraries of Leipzig in Germany announced in September that they had discovered a previously unknown piece in their collections, probably composed by a young Wolfgang Amadeus Mozart.

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Associated Press video journalist John Minchillo in New York contributed to this story.

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Follow Philip Marcelo at twitter.com/philmarcelo.