How did Alexander Calder experiment with sound in Small Sphere and Heavy Sphere?

In his 1932–33 work Small Sphere and Heavy Sphere, Alexander Calder experimented with sound by positioning various utilitarian objects on the floor. He then suspended two balls from the ceiling on wires, which were intended to strike these objects as they moved, thereby creating a variety of sounds.1

This piece was part of Calder’s broader exploration of mechanical motion, which he began after a visit to the studio of Piet Mondrian inspired him to move toward abstract art. These early experiments with motion and sound were instrumental in his development of the mobile, a form for which he later became world-renowned.12