His second prototype was keyboard - based but used a radio frequency oscillator as well .
The first version was similar to a Theremin , but Mager 's design had the capability to change the timbre of the sound that was produced as well as utilize discrete pitches .
Mager 's second prototype was keyboard - based but used a radio frequency oscillator as well .
The first version was similar to a Theremin , but Mager 's design had the capability to change the timbre of the sound that was produced as well as utilize discrete pitches .