An unknown waltz by Chopin, written nearly 200 years ago, has been discovered in the vault of the Morgan Library and Museum in New York.

The score, on a card bearing Frédéric Chopin’s hand-written name, was found by a curator in the spring, the New York Times reported on Sunday.

“I thought, ‘What’s going on here? What could this be?’ I didn’t recognise the music,” curator Robinson McClellan told the paper.

He was at first unsure that the piece was actually Chopin’s after photographing the score and playing it on a keyboard at home.

He conferred with an academic at the University of Pennsylvania who is an expert on the Polish composer, before the Morgan concluded the find was genuine after testing the ink and paper.

The penmanship was also found to match Chopin’s, including the reproduction of a stylised bass clef symbol as well as doodling characteristic of the composer.

“We have total confidence in our conclusion,” McClellan said.

The finding may prompt debate in the classical music field, where reports of unearthed masterpieces are sometimes greeted sceptically, and where there is a history of fakes and forgeries, the New York Times reported.

Newly discovered works by Chopin, who died in 1849 at 39, are rare. While he is one of music’s most beloved figures – his heart, pickled in a jar of alcohol, is encased in a church in Warsaw – he was less prolific than other composers, writing about 250 pieces, almost entirely for solo piano.

The museum believes that the music is from between 1830 and 1835, when Chopin was in his early 20s.

The tune features a stark opening and was described by pianist Lang Lang as containing “dramatic darkness turning into a positive thing”.

With Agence France-Presse