The Hammond-organ is an electric organ, invented by Laurens Hammond and John M. Hanert (6) and first manufactured in 1935. (7) Different models were made, of which most use sliding drawbars to specify a variety of sounds. Up to 1975, Hammond organs produced sound by creating an electric current by turning a metal tone wheel near an electromagnetic pickup and then amplifying the signal by means of an amplifier, so it can drive a speaker cabinet. Around two million Hammond organs were manufactured. The organ is often used with and associated with the Leslie speaker. The organ was originally released and sold by the Hammond Organ Company (1970/1975) to churches as a cheaper alternative to the wind-driven pipe organ, or instead of a piano. It quickly became popular among professional jazz musicians in organ trios.