At the factory, two experienced workers, David Gonzalez and Joseph Guarascio, began taking the Cole Porter piano apart with help from their boss, Bill Youse. As they took the lid off and reached inside, one was tempted to steal a line from another Cole Porter hit. They were going deep in the heart of it.

Before long Mr. Gonzalez, who has worked at Steinway for 29 years, and Mr. Guarascio, who has worked there for 16, slid the entire keyboard out, along with the hammers that strike the strings. They loosened the tuning pins and snipped the thick, copper-wound bass strings. They lifted out the cast iron plate, exposing the soundboard.

Eventually, they will cut that out, leaving the familiar curved rim and the legs, the skeleton of the Cole Porter Steinway, No. 129281. Steinway has numbered every piano it has made in its 165-year history. The Cole Porter piano, finished in 1907 and sold in 1908, was the 129,281st.

Where the piano was for its first 28 years is a mystery, at least to Steinway, whose records show that it was delivered to an address on West 81st Street in Manhattan in 1908. The next date in Steinway’s handwritten ledger is from 1945, when the piano was sent back for repairs.

The Porter biographer William McBrien did not explain the gap but did explain how Porter came to have No. 129281. It was a gift from the Waldorf’s management after he moved in, in the 1930s.

Porter lived a grand life, and his suite at the Waldorf was, appropriately enough for the composer of “You’re the Top,” near the top. Mr. McBrien described the room the piano was in as “cathedral-like.” It must have been, not just because No. 129281 is almost seven feet long but because it was not the only piano on the premises. “Porter decorated the suite with two grand pianos placed curve to curve, the players facing,” Mr. McBrien wrote.