Mager invented two different variants of the Sphärophon. 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. His second prototype was keyboard-based but used a radio frequency oscillator as well. This instrument was capable of producing quarter tones of an octave. In many of his instruments, including the Spharophon, Mager experimented with the drivers in the loudspeakers to achieve different sounds as well.
Mager premiered his special new instrument at the Donaueschingen Festival, Germany in 1926. The festival had been started in 1921 to promote new types of music and still continues to this day in the town of Donaueschingen in southwest Germany, just north of Zurich, Switzerland,
All that is known about the Spharophon is from pictures, witnesses' accounts, and written records. There are no Spharophons in existence today because they were all destroyed along with all of Mager's instruments such as the Partiturophon and the Kaleidophon during World War II.