Editing Ring modulation (section)

== Applications ==
=== Radio communications ===
Ring modulation has also been extensively used in [[radio receiver]]s, for example, to [[demodulate]] an [[FM broadcasting|FM]] stereo signal, and to heterodyne microwave signals in mobile telephone and wireless networking systems. In this case, the circuit is sometimes called a ''ring demodulator'', one of many possible [[Chopper (electronics)|chopper circuits]].<ref name="Meikle 2008 336"/><ref name="Yadav 2008 83"/> A ring modulator can be used to generate a double-sideband suppressed-carrier (DSB-SC) wave used in radio transmission.<ref name="T G Thomas S Chandra Sekhar 2005 37"/>

=== Music and sound effects ===
{{listen
 | header       = Audio samples of the ring modulation effect:
 | filename     = Ring_Modulation-Original_sample.ogg
 | title        = Unprocessed original sample
 | description  =
 | format       =
 | filename2    = Ring_Modulation-with_2500Hz.ogg
 | title2       = Ring modulation with a 2500 Hz sound
 | description2 = Notice the bell-like sound.
 | format2      =
 | filename3    = Ring_Modulation-with_sweep_to_9kHz.ogg
 | title3       = Ring modulation with an exponential sweep from 0 Hz to 9 kHz
 | description3 = On lower modulation frequencies, the ring modulation is perceived as a tremolo effect (as in the first part of the sound)
 | format3      =
}}

One of the earliest musical instruments utilizing a ring modulator was the ''Melochord'' (1947) built by [[Harald Bode]]. It was a two-tone melody keyboard instrument with foot controllers and later added a second keyboard for timbre control, featuring a white-noise generator, envelope controller, formant filters and ring modulators for harmonics.<ref name="palov"/> The early Melochord was extensively used by [[Werner Meyer-Eppler]] in the early days of the electronic music studio at [[Bonn University]].<ref name="melo"/> Meyer-Eppler mentioned the musical application of ring modulator in his book ''Elektrische Klangerzeugung'', published in 1949.<ref name="meyer-eppler1949"/>

Meyer-Eppler's student [[Karlheinz Stockhausen]] used ring modulation in 1956 for some sounds in ''[[Gesang der Jünglinge]]'' and his realization score for ''[[Telemusik]]'' (1966<ref name="Collins">[[Nick Collins (composer)|Collins, Nick]] (2010). ''[https://books.google.com/books?id=mCpqmESEOEcC&pg=PA124 Introduction to Computer Music]'', pp. 124-125. John Wiley & Sons. {{ISBN|9780470714553}}.</ref>) also calls for it. Indeed, several entire compositions by Stockhausen are based around it, such as ''[[Mixtur]]'' (1964), one of the first compositions for orchestra and live electronics; ''[[Mikrophonie (Stockhausen)|Mikrophonie II]]'' (1965), where the sounds of choral voices are modulated with a [[Hammond organ]]; ''[[Mantra (Stockhausen)|Mantra]]'' (1970),<ref name="Collins"/> where the sounds from two pianos are routed through ring modulators; and ''Licht-Bilder'' (2002) from ''[[Sonntag aus Licht]]'' (2003),<ref name="Roads"/> which ring-modulates flute and trumpet.<ref name="Brümmer 2008"/><ref name="Stockhausen 1996"/><ref name="Stockhausen 2005"/> Other Stockhausen pieces employing ring modulation include ''[[Kontakte]]'' (1960),<ref name="Roads"/> ''Mikrophonie I'' (1964),<ref name="Roads"/> ''[[Hymnen]]'' (1969),<ref name="Roads"/> ''[[Prozession]]'' (1967),<ref name="Roads"/> and ''[[Kurzwellen]]'' (1968).<ref name="Roads"/>

A ring-modulator was the major component used in [[Louis and Bebe Barron]]'s music for the film ''[[Forbidden Planet]]'' (1956). One of the best-known applications of the ring modulator may be its use by [[Brian Hodgson]] of the [[BBC Radiophonic Workshop]] to produce the distinctive voice of the [[Dalek]]s in the [[television series]] ''[[Doctor Who]]'', starting in 1963.<ref name="Jeremy Bentham"/>

One of the first products dedicated for music was the ''Bode Ring Modulator'' developed in 1961 by [[Harald Bode]]. Also in 1964 he developed the ''Bode Frequency Shifter,'' which produced a clearer sound by eliminating a side band.<ref name="HaraldBodeLifetime"/> These devices were designed to be controlled by voltage, compatible with modular synthesizer architecture also advocated by him,<ref name="bode1961"/> and these modules were licensed to [[R.A. Moog]] for their [[Moog modular synthesizer]]s started in 1963–1964.<ref name="TomRhea2004"/> In 1963, [[Don Buchla]] included an optional ring modulator in his first modular synthesizer, the [[Buchla|Model 100]].<ref name="Buchla"/> Also [[Tom Oberheim]] built a ring modulator unit for [[The United States of America (band)|his musician friend]] in the late 1960s,<ref name="oberheim1970"/><ref name="oberheim2008"/> and it became an origin of [[Oberheim Electronics]] ''Music Modulator''<ref name="Oberheim Music Modulator"/> and ''[[Gibson Guitar Corporation#Brand names|Maestro]] Ring Modulator'',<ref name="maestroRM1A"/> one of the earliest ring modulator [[Effects unit|effect]] products for guitarists. The [[Electronic Music Studios|EMS]] [[VCS3]], [[Synthi A]], [[ARP 2600]], [[ARP Odyssey|Odyssey]], [[Rhodes Chroma]] and [[Yamaha CS-80]] synthesizers also featured built-in ring modulators.

[[John McLaughlin (musician)|John McLaughlin]] employs the ring modulator heavily in the 1974 [[Mahavishnu Orchestra]] album ''[[Visions of the Emerald Beyond]]'', especially on the track "On the Way Home to Earth". On [[Miles Davis]]' 1975 live album ''[[Agharta (album)|Agharta]]'', guitarist [[Pete Cosey]] ran the sounds he played through a ring modulator.<ref name="Trzaskowski"/> [[Deep Purple]]'s [[Jon Lord]] fed the signal from his Hammond through a Gibson Ring Modulator unit live on stage, which he described in 1989.<ref name="Lord Almighty"/><ref name="Jon Lord"/> Founding member of [[Hawkwind]], Dik Mik, a self-confessed non-musician, used a ring modulator as his main instrument during his time with the band (1969-1973).<ref name="Hawkwind"/>

[[Vangelis]] used a ring modulator with his [[Yamaha CS-80]] to improvise his 1978 avant-garde-experimental album ''[[Beaubourg (album)|Beaubourg]]''. The music on the album is often atonal, with the ring modulator converting the synthesizer's sound into complex metallic timbres.<ref name="BeaubourgReviewSynthopia"/> It remains the most experimental released work by the artist, with reviewers calling it "difficult listening at best".<ref name="BeaubourgReviewAllmusic"/>

Ring modulation is used in the piece ''Ofanim'' (1988/<!--revised-->1997) by [[Luciano Berio]], and in the first section is applied to a child's voice and a [[clarinet]]: "The transformation of the child voice into a clarinet was desired. For this purpose, a pitch detector computes the instantaneous frequency <math>f_0 (n)</math> of the voice. Then the child voice passes through a ring modulator, where the frequency of the carrier <math>f_c</math> is set to <math>f_0 (n)/2</math>. In this case odd harmonics prevail which is similar to the sound of a clarinet in the low register."<ref name="DAFX">Zölzer, Udo; ed. (2002). ''[https://books.google.com/books?id=h90HIV0uwVsC&pg=PA75 DAFX - Digital Audio Effects]'', p.76-7. John Wiley & Sons. {{ISBN|9780471490784}}.</ref>{{failed verification|reason=may verify the math but does not verify the quote|date=March 2020}}

=== Analogue telephone systems ===
An early application of the ring modulator was for combining multiple analog telephone voice channels into a single wideband signal to be carried on a single cable using [[frequency-division multiplexing]]. A ring modulator in combination with [[carrier wave]] and filter was used to assign channels to different frequencies.

Early attempts at [[Privacy|securing]] analog telephone channels used ring modulators to modify the spectrum of the audio speech signals. One application is spectral inversion, typically of speech; a carrier frequency is chosen to be above the highest speech frequencies (which are low-pass filtered at, say, 3&nbsp;kHz, for a carrier of perhaps 3.3&nbsp;kHz), and the sum frequencies from the modulator are removed by more low-pass filtering. The remaining difference frequencies have an inverted spectrum: high frequencies become low, and vice versa.