Lev Sergeyevich Termen (27 August 1896 – 3 November 1993), or Léon Theremin in the United States, was a Russian and Soviet inventor, most famous for his invention of the theremin, one of the first electronic musical instruments and the first to be mass-produced. He also devised the interlace technique for improving the quality of a video signal, still widely used in video and television technology.