Whose voice was recently discovered to have been recorded on one of Thomas Edison's early voice-recording devices?

In 1957, a box of wax recording cylinders was discovered in the laboratory of Thomas Edison. Until 2011, however, its contents remained a mystery.

Now, a combination of digital conversion and historical research has identified them as a series of long-sought recordings made by Edison's assistant Adelbert Wangemann on a trip to Europe, during which he demonstrated Edison's newly-perfected phonograph to such luminaries as German chancellor Otto von Bismarck, Prussian officer Helmuth von Moltke, and Kaiser Wilhelm II.

The recordings capture the voice of von Moltke, as well as what is believed to be the first recording of a work by Chopin. Perhaps most importantly, they also provide the only recording of Otto von Bismarck's voice, in which he recites pieces from several songs, ending with advice to his son Herbert, who apparently heard the recording weeks later in Budapest. Bismarck historians had known of the cylinder, but after years of searching, they assumed that it had been destroyed.