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, but it was known in the Soviet Union as the or , in Germany as the Thereminvox and later, in the USA, as the theremin.

On 24 May 1924 Theremin married 20-year-old Katia Konstantinova, and they lived together in his parents' apartment on Marat street. In 1925 Theremin went