The Hammond organ is an electric organ invented by Laurens Hammond and John M. Hanert, first manufactured in 1935. Multiple models have been produced, most of which use sliding drawbars to vary sounds. Until 1975, sound was created from rotating a metal tonewheel near an electromagnetic pickup, and amplifying the electric signal into a speaker cabinet. The organ is commonly used with the Leslie speaker.
Around two million Hammond organs have been manufactured. The organ was originally marketed by the Hammond Organ Company to churches as a lower-cost alternative to the wind-driven pipe organ, or instead of a piano. It quickly became popular with professional jazz musicians in organ trios—small groups centered on the Hammond organ. Jazz club owners found that organ trios were cheaper than hiring a big band. Jimmy Smith's use of the Hammond B-3, with its additional harmonic percussion feature, inspired a generation of organ players, and its use became more widespread in the 1960s and 1970s in genres such as rhythm and blues, rock (especially progressive rock), and reggae.