I recently learned that an unknown waltz by the eminent composer Chopin, written nearly 200 years ago, had been discovered in the vault of the Morgan Library & Museum in New York. It was unearthed in a collection of memorabilia, alongside postcards signed by Picasso and letters from Brahms and Tchaikovsky.We published our exclusive story on the discovery today. And here’s a special treat: The superstar pianist Lang Lang recorded the waltz for The Times. You can watch his performance here. The story of the long-lost waltz starts at the Morgan on a late-spring day, when the curator and composer Robinson McClellan came across an unusual musical manuscript. The piece was moody and melancholic, and a conspicuous name was written across the top: Chopin.
McClellan took a photo on his iPhone so he could play the piece back at home on his electric piano. He also sent a photo to Jeffrey Kallberg, a Chopin scholar at the University of Pennsylvania.
“My jaw dropped,” Kallberg told me. “I knew I had never seen this before.”
In September, the Morgan’s experts invited me to view the manuscript, which they had authenticated by analyzing the paper, ink and musical style. It was much smaller than I had imagined — a pockmarked scrap about the size of an index card. Chopin had famously tiny penmanship, and he packed a lot into this little piece.
As an amateur pianist, I grew up adoring Chopin’s music. His waltzes, nocturnes, ballades and mazurkas are a dreamy realm of nostalgia, longing, suffering and bliss. He is still one of music’s most beloved figures. (His heart, pickled in a jar of alcohol, is encased in a church in Warsaw.)
After viewing the manuscript, I spent weeks immersed in Chopin’s world. I studied his scores, letters and sketches, and listened to recordings of his waltzes, searching for clues about the unusual piece found at the Morgan. I tracked down the previous owners of the manuscript: a Connecticut family that was not aware of its importance. I delighted in working through the waltz in a practice room near Lincoln Center, wondering if anyone nearby had any idea what I was playing.
Newly discovered works are rare in classical music, especially for Chopin, who was less prolific than other composers. We knew that readers would want to hear the waltz, but we needed a pianist who could do it justice. I immediately thought of Lang Lang, one of the biggest stars in classical music, whom I first met in 2016 when I was a China correspondent for The Times in Beijing.
I messaged Lang on WeChat, asking if he’d be interested in being part of an “unusual story.”
“What kind of unusual story 
,” he wrote back. I told him about the newly discovered Chopin and sent him the score, which he played through before a rehearsal in San Francisco.
“Wow this is a great piece!” he said in a voice message. “I’m very surprised. It’s very Chopin. It must be Chopin. It sounds very much like Chopin, with a very dramatic darkness turning into a positive thing. It’s beautiful.”
While Lang was in New York earlier this month to open Carnegie Hall’s season, I met up with him at Steinway Hall in Manhattan to record the waltz. He adjusted his interpretation after each take, changing the tempo and refining the quiet opening notes. He joked that the piece sounded like the beginning of a Woody Allen movie.
Sitting near the piano, I asked him why people should care about this waltz, 175 years after Chopin’s death.
“This level of music making — it always touches us the deepest,” he said. “To have a new work by this level of great artist — we’re just so lucky. Just enjoy it.”
