This pair of bowed rod instruments, played side by side, provides two chromatic octaves of range. The sounding elements are threaded rods mounted on circular steel plates. The circular configuration allows bowing access to each of the rods individually, much as the violin’s arched bridge allows access to individual strings. The instruments are designed to sound not the fundamentals of the rods, but rather one of the overtones, producing a whistling tone. It takes a bit of practice to consistently produce the intended tone and not the fundamental or some other overtone; the trick is in bowing at just the right spot along the rod.