A tonewheel is a relatively primitive apparatus for generating electronic musical notes. The tonewheel assembly consists of a synchronous AC motor and an associated gearbox that drives a series of rotating disks. Each disk contains a set of bumps that generate a specific frequency through a corresponding pickup assembly, consiting of a magnet and coil. The frequency depends on the speed of rotation of the disk and the number of bumps. A single fundamental frequency can be combined with one or more harmonics to produce complex sounds. A tonewheel was used in the Teleharmonium and in the original Hammond organs.