The term is used in this article to denote pipeless electronic keyboard instruments that have the following three features in common with pipe organs: the ability to sustain the tone indefinitely, the ability to play chords (unlike certain electronic keyboard instruments which are monophonic), and the ability to increase or decrease any sustained tone, a function comparable with that of the Swell box of the pipe organ. In addition, most electronic organs have a wide selection of timbres, similar to the stops and mixtures of the acoustic instrument. In a few instances selected registers (e.g. 16' and 32' bass ranks) on a pipe organ have been created electronically.
After Lee de Forest was granted an American patent on his vacuum tube in 1906, the way was paved for the possibility of generating and amplifying musical sounds. However, it was not until after World War I that the first electronic organs were produced. The Coupleux-Givelet organ, named after its two French inventors, was first constructed in 1928; it used electronic oscillators to imitate and replace a pipe organ and had two or three manuals and a full pedal-board. Several of these instruments were built in the next few years and installed in churches; one was used at the Poste Parisien broadcasting station. In 1931 Richard H. Ranger demonstrated his Rangertone organ, developed from the principle of an interrupted light source in conjunction with photo-electric cells. Laurens Hammond in Chicago began to develop an organ for commercial production in 1933; the Hammond organ first appeared in 1935 and rapidly established itself – by the end of 1937 the company had sold over 3000 instruments. In 1934 the Orgatron, invented by Frederick Albert Hoschke, was marketed by the Everett Piano Co.; this used vibrating reeds as its sound source, and is thus classified as an Electric organ. It was taken over by the Wurlitzer Co. in 1946 and used as the basis of their electric organ until the mid-1960s.
The most significant differences between the various instruments lie in their manners of tone production. The electromechanical Hammond organ uses the principle of electromagnetic tone production with tone-wheels. For each frequency generated a profiled metal wheel rotates in close proximity to a coil-wound permanent magnet. As the wheel rotates it creates a disturbance in the magnetic field, inducing an alternating current in the coil. The number of projections passing the magnet per second gives the frequency; the waveshape is very close to a sine wave. Altogether 91 (later 96) such tone-wheels are used; all those producing pitches of the same pitch class rotate on the same shaft and all 12 shafts are driven by one synchronous motor. This ingeniously ensures that the instrument can never go out of tune within itself. The other characteristic principle of the Hammond organ is that of the drawbars (see Hammond organ, illustration): these govern the timbre by selecting pitches close to those of the harmonic series to sound along with the fundamental. Since these are drawn from the tone-wheel system, they are not true harmonics, but rather lie within equal temperament. This method does, however, provide a very wide range of timbre synthesis, limited mainly by the fact that partials only up to the 8th (and omitting the 7th) are employed. Preselected timbre combinations, usually given the names of common organ stops, are available by pressing tabs.
An English instrument which received the greatest praise for its faithfulness to acoustic models was the electromechanical Compton Electrone invented by Leslie Bourn. Its success in imitating acoustic organs was largely attributable to the fact that it could create a large number of harmonics by means of waveforms engraved on an electrostatic disc; there were 12 such discs, one for each of the notes of the octave, the pitch of each being determined by the speed at which an associated scanning disc revolved.
For all of these organs the quality of the sound is ultimately dependent on the quality of the loudspeakers. In more sophisticated instruments a large loudspeaker cabinet is usually separate from the console of the instrument, and can be placed in any convenient or acoustically advantageous position. Bearing in mind that many instruments are designed for the home, manufacturers now invariably incorporate some form of reverberation unit or electronic equivalent which can compensate for a very dry room acoustic. Often a special type of tremulant loudspeaker is incorporated or connected externally, particularly the Leslie, which contains a rotating curved reflector that causes interesting phase-change relationships and a distinctive quality of sound.
Each of the principles of tone production so far discussed has relied upon some electro-acoustic or electromechanical device. By far the most common source used in electronic organs from the 1940s to the early 1980s, however, was that of the electronic oscillator, one per note in the more expensive instruments, otherwise a set of 12 oscillators, one for each pitch class, in conjunction with frequency dividers – electronic circuits that produce one cycle for every two at their input – or a single master oscillator with two sets of frequency dividers. Commonly the 12 source oscillators generate the frequencies of the top octave of the organ, while the frequency dividers are used to derive each lower octave. Although each set of octaves derived from a single source oscillator is perfectly in tune with the rest, there are disadvantages with this system: frequency dividers naturally generate the square wave-form, which, containing only odd harmonics, is suitable primarily for simulating stopped organ pipes. Sawtooth waves, which contain all harmonics, are necessary to simulate open organ pipes and these can only be approximated by mixing square waves of particular frequencies and amplitudes. With a harmonically rich waveform, however, the number of ‘stops’ available by means of switching in different formant filters is limited only by expense. Size is not so much a problem, since the valves used in electronic organs up to the 1960s were superseded first by solid-state transistors and then by integrated circuits; from the 1980s the sounds have been generated digitally (pioneered in the Allen organ from 1971), more recently based on sampled timbres. Most analogue electronic organs are fully polyphonic, with a separate oscillator or frequency divider for each note; digital organs have frequently had fewer, up to the late 1990s often with only 16 oscillators, at the end of the 20th century normally with 32 or 64 (most keyboards comprise 61 notes).
The question of the identity and function of the electronic organ is an interesting one. At one extreme it has nearly always been related to the church organ, to be compared with it, usually unfavourably, although special church models often offer a choice of completely different registrations, and Hammond church organs have omitted the ‘out of tune’ overtones. Expensive concert models have been produced by several companies, especially by Allen and Yamaha (Electones), and electronic instruments largely replaced pipe-based cinema organs. The electronic organ began to find a niche in popular music in the 1950s, especially with portable models suitable for small bands; in the 1960s ‘combo’ organs, such as the Farfisa Compact and Vox Continental, had considerable success. But it has found its greatest popularity as a home entertainment instrument; organs designed for this area of the market now often include a range of special effects and features, such as rhythm and ‘walking bass’ units, arpeggiators, memories and a choice of chord systems. In the late 1970s the development of the polyphonic synthesizer began to blur the differences between the two types of instrument; larger digital organs still retain their uniqueness, even though composers such as Stockhausen have chosen synthesizers instead of electronic organs in recent performances of their earlier works. (For further discussion of the development of the electronic organ since 1945, see Electronic instruments, §IV, 3.)
For instruments classifiable as electronic organs see Allen organ; Baldwin organ; Bode, Harald; Hammond organ; Korg; Lowrey organ; Roland; Yamaha. Other significant electronic organ manufacturers or specific models (including ‘organ modules’) have included Ahlborn, AWB, Bradford Computing organ, Cellulophone, Conn, Copeman Hart, Dereux, Elka, Gulbransen, Johannus, KdF-Grosstonorgel, Kimball, Kinsman, Kristadin, Lichtton-Orgel, Magneton, Makin, Mastersonic, Midgley-Walker, Miller, Minshall, Norwich, Novachord, Organo, Philicorda, Rodgers, Syntronic organ, Thomas, Tuttivox, Vierling, Voce, Wyvern and Yunost'. Electronic organs are classified according to different methods of sound production in Electronic instruments, §I, 3(i) and 4.
GroveJ (A. Shipton)
MGG1 suppl. (W. Lottermoser)
J. Castellan: ‘Les grandes orgues et l'électricité’, Science et vie, lxxi (1947), 115–26
A. Douglas: The Electronic Musical Instrument Manual: a Guide to Theory and design (London, 1949, 6/1976)
R.H. Dorf: Electronic Musical Instruments (Mineola, NY, 1954, 3/1968) [rev. version of articles orig. pubd in Radio-Electronics, 1950–52]
R.L. Eby: Electronic Organs: a Complete Catalogue, Textbook and Manual (Wheaton, IL, 1953)
N.H. Crowhurst: ‘Electronic Organs’, Audio, lii/9–liii/5 (1958–9) [series of articles]; rev. in Electronic Organs (Indianapolis, IN, 1960, 3/1975)
W.H. Barnes: The Contemporary American Organ: its Evolution, Design and Construction (Glen Rock, NJ, 7/1959), 347–62
H.E. Anderson: Electronic Organ Handbook (Indianapolis, IN, 1960)
S. Irwin: Dictionary of Electronic Organ Stops: a Guide to the Understanding of the Stops on all Electronic Organs (New York, 1968)
W. van Bussel: Elektronische Orgels (Utrecht and Antwerp, 1972)
J.H.M. Goddijn: Groot elektronisch orgelboek (Deventer, 1975)
M. Rieländer: Die elektronische Orgel (Frankfurt, [1975])
B. Drukker and H. Goddijn: Handboek elektronische orgels en synthesizers (Deventer and Antwerp, 1978)
E. Peterson: ‘The Rich History of the Electronic Organ’, Keyboard, ix/11 (1983), 32–6
M. Vail: ‘The Rhodes Piano Bass and the Vox Continental: the Original Doors Keyboards’, Keyboard, xvii/2 (1991), 100–01; rev. in Vintage Synthesizers: Groundbreaking Instruments and Pioneering Designers of Electronic Music Synthesizers (San Francisco, 1993), 223–6
B. Carson: ‘'60s Combo Organs: Turn On – Tune In – Rock Out! – Tweezy – Twerpy – Trendy’, Keyboard, xix/6 (1993), 48–67; rev. in M. Vail: Vintage Synthesizers: Groundbreaking Instruments and Pioneering Designers of Electronic Music Synthesizers (San Francisco, 1993), 227–39
For further bibliography see Electronic instruments.
RICHARD ORTON/HUGH DAVIES