An electronic device used in both recorded and live electronic music. It is a standard item in electronic music studios, and can appear as a free-standing unit connected to other electronic apparatus, or as a module within a synthesizer. Existing in both analog and digital forms, the ring modulator takes its name from the characteristic ring formation of four diodes in its analog circuit (see illustration).
There are broadly two classes of instruments in an electronic music studio: sound generators and sound modifiers. The ring modulator is a sound modifier. It modifies the frequency components of a given sound (henceforward the ‘signal’), according to definite laws, in relation to those of a second source, or ‘carrier’. So a ring modulator has two inputs, the signal input and the carrier input, and one output. The modulator will function only if both inputs are present, and optimally when they are balanced, i.e. present at the same amplitude. The output consists of the sum and difference frequencies of those at the inputs. For example, if sine waves (i.e. pure tones) of frequencies 1000 Hz and 400 Hz are present at the inputs, the output will consist of the two frequencies 1400 Hz and 600 Hz. In practice, it matters little which input is regarded as the signal and which the carrier, since it is only the modulation products that matter. These products are called ‘sidebands'.
In the above example, where sine waves were the input signals, only two frequencies were contained in the output. If one of the inputs is changed to a more complex form, such as a square wave, then each of the harmonic partials contained within that input is modulated, and so the output is much more complex. Each harmonic generates a sideband not related to the harmonic series. This applies, of course, to any more complex sound at either of the inputs. Each instantaneous frequency component at one input is modulated with each instantaneous frequency component at the other input. With a varying input such as that often obtained in live electronic music from an instrumental source, the aural result is not precisely predictable.
Ring modulators may be used in studios to create new and complex sound mixtures, or to effect various transformations upon material. For example, a musical signal may be modulated with a low-frequency sine wave (say 5 Hz), to produce a strange amplitude-modulation effect. Related to this is the use of a pulse or any other very short carrier input to ‘gate’ the signal input. Another characteristic result of the ring modulator is the creation of multiple glissandos when one of the input signals is varied in frequency. It should be noted that, as in the 5 Hz example, the input signals need not be within the audio range. As long as at least some of the sidebands lie within it there will, of course, be an audible result. The device known as the ‘frequency shifter’ or ‘Klangumwandler’ exploits this. A double ring-modulation process heterodynes the signal into a higher frequency range and back again, isolating the upper or lower sideband. The signal is shifted in frequency by the amount of the frequency of the carrier, the direction of the shift depending on which sideband has been isolated.
Several works by Stockhausen can be cited as exemplifying the use of the ring modulator. In Mixtur (1964) the sounds of four groups of instrumentalists are picked up by microphones and fed into the signal inputs of four ring modulators. The carrier input of each is a full-range sine-wave oscillator operated by separate musicians. The frequencies of the carrier sine waves are varied throughout the composition, and the modulated sounds, amplified and reproduced through four loudspeakers, blend with the live orchestral sound. In Mantra (1969–70) the sounds of two pianos are presented to the signal inputs of two ring modulators, the carrier inputs again being sine waves. Ring-modulation techniques are applied to recorded materials in the tape compositions Telemusik (1966) and Hymnen (1966–7).
Other composers to have used ring modulation in conjunction with acoustic instruments include Ichiyanagi (Appearance, 1967), Ivan Tcherepnin (Rings, 1967), Smalley (Transformation I, 1968–9; Pulses, 1969; Monody, 1971–2), Cristóbal Halffter (Noche activa del espiritu, 1973), Kelemen (Mirabilia, 1975) and Stahmer (Kristallgitter, 1992). Subotnick's ‘ghost box’, which he began to use in 1977, altered ring modulation, frequency and amplification to vary the sounds of a live performer. Known colloquially as the ‘fuzz box’, the ring modulator has also been extensively and imaginatively employed in ‘electric jazz’ and in pop music.
H. Bode: ‘The Multiplier-Type Ring Modulator, Electronic Music Review, no.1 (1967), 9
K. Stockhausen: Texte zur Musik 1963–1970 (Cologne, 1971), 51ff, 66ff, 75ff
A. Strange: Electronic Music: Systems, Techniques and Controls (Dubuque, IA, 1973, 2/1983), 9–11
S. Emmerson: ‘Ring Modulation and Structure’, Contact, no.17 (1977), 14–20
H. Bode: ‘The History of Electronic Sound Modification’, Journal of the Audio Engineering Society, xxxii/10 (1984), 730–39
C. Dodge and T.A. Jerse: Computer Music: Synthesis, Composition and Performance (New York, 1985, 2/1997)
RICHARD ORTON/R