While adapting the dielectric device by adding circuitry to generate an audio tone, Theremin noticed that the pitch changed when his hand moved around. In October 1920 he first demonstrated this to Ioffe who called in other professors and students to hear. Theremin recalled trying to find the notes for tunes he remembered from when he played the cello, such as the Swan by Saint-Saëns. By November 1920 Theremin had given his first public concert with the instrument, now modified with a horizontal volume antenna replacing the earlier foot-operated volume control. He named it the "etherphone", to be known as the Терменвокс (Termenvox) in the Soviet Union, as the "Thereminvox" in Germany, and later as the "theremin" in the United States.