A rolling stone gathers no moss as they say, but this collection of stones manipulated by electromechanical devices are capable of performing George Harrison’s “Here Comes the Sun” thanks to artist Neil Mendoza. Titled Rock Band, this kinetic sound art installation is actually four different instruments including a xylophone, a buzzing base, two spinners, and a pair of slappers. Mendoza describes how each device works:
Xylophone: Inside each of the tubes is a small pebble. When the Teensy receives a note for this instrument, it triggers a solenoid (electromagnet), to launch the pebble up a tube and strike a key. For the design of this piece, I wrote a piece of software that calculated the size each key needed to be to produce the appropriate frequency and then cut them out using a water jet cutter.
Bass: This is the small marble circle in the front. When the Teensy receives a note for this one, it causes the plunger of a solenoid (electromagnet) to vibrate at the frequency of the appropriate musical note against the rock.
Spinners: These are the two large objects on either side and are percussive. Inside each of these, there are two magnets attached to each end of a shaft. On the outside, there are two magnetic rocks, Hematite, that are attracted to the magnets on the inside. When a note is received, the shaft spins and one of the rocks is guided away from its magnet and launched through the air. It lands on a piece of marble that has been cut to size to fit in the machine.
Slapper: These slap the rocks with pieces of fake leather and provide some light percussion.