Savart’s Wheel is tuned rasp. It consists of 30 wooden disks of graduated sizes on a motor-driven spindle. The edge of each disk is surfaced with ridges spaced about one eighth inch apart. As the spindle turns, the player holds a special plectrum against the ridged edge of one of the disks. However many ridges rotate past per second is the frequency that sounds. With disks of different diameters, the ridges-per-second numbers are different, so by holding the plectrum against different disks you get different notes. The plectrum has an attached radiating surface in the form of a styrofoam cup. The cup acts as a soundboard, projecting the sound out into the air.
In the audio clip, Savart’s Wheel is backed by a wannabe rock band. A video of this instrument can be found among the demonstrations in this youtube playlist.