Signedon third front wheel, stamped: illegible
FunctionThis instrument was used to produce specific sounds by letting a rigid card come into contact with the rotating wheels. If the wheels rotate at a constant speed, putting two cards on separate wheels can generate different kinds of pitches. For instance, owing to the number of teeth on these wheels, the diatonic scale can be entirely reproduced. For instance, the 9/8 tone with the 1st and 2nd wheels; the 4/3 tone with the 2nd and 5th wheels; the 15/8 tone with the 1st and 8th wheels, etc.
The French physicist Félix Savart (1791-1841) devised this system of generating sound frequencies and used these toothed wheels to try to determine the upper limit of audible frequencies.