The idea of a polyphonic keyboard on wheel instruments derives from my studies about 12th century Organistrum.
The three strings are tuned to the same pitch (C), eight tangents being distributed among them: two on the first string, three on the middle one and three on the third.
Thus it is possible to play not only a melody accompanied by drones, but some double stops (fourths and thirds) too.
I introduce you SONYA, the polyphonic symphonia.
Diapason: cm. 43