LEON THEREMIN led a life of flamboyant musical invention laced with daring electronic stealth. A creative genius and prolific inventor, Theremin launched the field of electronic music virtually singlehandedly in 1920 with the musical instrument that bears his name. The theremin -- the only instrument that is played without being touched -- created a sensation worldwide and paved the way for the modern synthesizer. Its otherworldly sound became familiar in sci-fi films and even in rock music. This magical instrument that charmed millions, however, is only the beginning of the story.

As a...