Last month, a German library unearthed a previously unknown Mozart composition — a very, very deep cut, if you will. Now, a Manhattan museum curator has found what appears to be a long-lost composition by Frédéric Chopin,

After testing the manuscript’s paper and ink, analyzing its handwriting and musical style, and consulting outside experts, the Morgan has come to a momentous conclusion: The work is likely an unknown waltz by Frédéric Chopin.

Deep in the vault of the Morgan Library & Museum in Manhattan on a late-spring day, the curator Robinson McClellan was sorting through a collection of cultural memorabilia. There were postcards signed by Picasso,