Then showed the paper on the overhead projector. Five ragged holes had been burned into the paper by the vibrating balls. Vibrating ball bearings burn 5 holes into a sheet of typing paper. A piece of grooved aluminum, Bolt heads fit the grooves and are attached to springs with a ball like mass on the end. Start the balls at the top and they vibrate with a wonderful sound to the bottom.
Balls vibrating in grooves noisily bounce their way down to the bottom.
I twirled the three foot long children's toy whirly playing a series of notes up and down the scale. I fell in love with the sounds of the whirly the first time I heard one. Whirlies only play notes which sound good together. No matter how I swing it around, it only plays certain notes. It does not slide from note to note it jumps.