The Leslie speaker is a specially constructed amplifier

Amplifier

Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...

/loudspeaker

Loudspeaker

A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...

 used to create special audio effects using the Doppler effect

Doppler effect

The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...

. Named after its inventor, Donald Leslie

Donald Leslie

Donald James Leslie, created and manufactured the Leslie speaker that refined the sound of the Hammond organ and helped popularize electronic music....

, it is particularly associated with the Hammond organ

Hammond organ

The Hammond organ is an electric organ invented by Laurens Hammond in 1934 and manufactured by the Hammond Organ Company. While the Hammond organ was originally sold to churches as a lower-cost alternative to the wind-driven pipe organ, in the 1960s and 1970s it became a standard keyboard...

 but is used with a variety of instruments as well as vocals. The Hammond/Leslie combination has become an element in many genres of music. The Leslie Speaker and the Hammond Organ brand

Brand

The American Marketing Association defines a brand as a "Name, term, design, symbol, or any other feature that identifies one seller's good or service as distinct from those of other sellers."...

s are currently owned by Suzuki Musical Instrument Corporation

Suzuki Musical Instrument Corporation

is a Japanese company that produces a range of musical instruments.-History:Suzuki was founded in 1953, as a harmonica manufacturer.Suzuki's western U.S...

.
Don Leslie, at the outset, was refused hire by the Hammond Organ

Hammond organ

The Hammond organ is an electric organ invented by Laurens Hammond in 1934 and manufactured by the Hammond Organ Company. While the Hammond organ was originally sold to churches as a lower-cost alternative to the wind-driven pipe organ, in the 1960s and 1970s it became a standard keyboard...

 Company, but did work for the local electric company, in a contract with Hammond, to replace the old fifty cycle rotor tone generators

Tonewheel

A tonewheel is a simple electromechanical 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...

 with the new sixty cycle units, in customers' homes.