page_title: Hammond organ
section_title: Tone generation
hierarchical_section_title: Hammond organ / Tone generation
caption_attribution_description: Deutsch: Seltener Blick auf die Tonräder des Tongenerators einer Hammond CV von 1946.
context_page_description: The Hammond organ is an electric organ invented by Laurens Hammond and John M. Hanert and first manufactured in 1935. Various models have been produced, most of which use sliding drawbars to vary sounds. Until 1975, Hammond organs generated sound by creating an electric current from rotating a metal tonewheel near an electromagnetic pickup, and then strengthening the signal with an amplifier to drive 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 rhythm and blues, rock, reggae, and progressive rock.
context_section_description: Although they are sometimes included in the category of electronic organs, the majority of Hammond organs are, strictly speaking, electric or electromechanical rather than electronic organs, because the sound is produced by moving parts rather than electronic oscillators.
  The basic component sound of a Hammond organ comes from a tonewheel. Each one rotates in front of an electromagnetic pickup. The variation in the magnetic field induces a small alternating current at a particular frequency, which represents a signal similar to a sine wave. When a key is pressed on the organ, it completes a circuit of nine electrical switches, which are linked to the drawbars. The position of the drawbars, combined with the switches selected by the key pressed, determines which tonewheels are allowed to sound. Every tonewheel is connected to a synchronous motor via a system of gears, which ensures that each note remains at a constant relative pitch to every other. The combined signal from all depressed keys and pedals is fed through to the vibrato system, which is driven by a metal scanner. As the scanner rotates around a set of pickups, it changes the pitch of the overall sound slightly. From here, the sound is sent to the main amplifier, and on to the audio speakers.
  The Hammond organ makes technical compromises in the notes it generates. Rather than produce harmonics that are exact multiples of the fundamental as in equal temperament, it uses the nearest-available frequencies generated by the tonewheels. The only guaranteed frequency for a Hammond's tuning is concert A at 440 Hz.
  Crosstalk or "leakage" occurs when the instrument's magnetic pickups receive the signal from rotating metal tonewheels other than those selected by the organist. Hammond considered crosstalk a defect that required correcting, and in 1963 introduced a new level of resistor–capacitor  filtering to greatly reduce this crosstalk, along with 50–60 Hz mains hum. However, the sound of tonewheel crosstalk is now considered part of the signature of the Hammond organ, to the extent that modern digital clones explicitly emulate it.
  Some Hammond organs have an audible pop or click when a key is pressed. Originally, key click was considered a design defect and Hammond worked to eliminate or at least reduce it with equalization filters. However, many performers liked the percussive effect, and it has been accepted as part of the classic sound. Hammond research and development engineer Alan Young said, "the professionals who were playing popular music [liked] that the attack was so prominent. And they objected when it was eliminated."
caption: Rare view of the tone wheels (underside of the generator)
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