Leon Theremin (1896-1993), born Lev Termen, Russian and Soviet engineer. Theremin was the inventor of the first electric musical instrument, known as a theremin after his later name Leon Theremin. The instrument was based on the heterodyne principle, and was played without touch by moving the hands through the air around the antennae. After a period touring and working in Europe and the USA, Theremin returned to USSR in 1938, and later invented the first covert listening device. He returned to the USA in 1991, dying at the age of 97. Photographed on the 3rd of May 1928.