Polyphony is a property of musical instruments that means that they can play multiple independent melody lines simultaneously. Instruments featuring polyphony are said to be polyphonic. Instruments that are not capable of polyphony are monophonic or paraphonic.
A monophonic synthesizer or monosynth is a synthesizer that produces only one note at a time, making it smaller and cheaper than a polyphonic synthesizer which can play multiple notes at once. This does not necessarily refer to a synthesizer with a single oscillator; The Minimoog, for example, has three oscillators which are settable in arbitrary intervals, but it can play only one note at a time.
Duophonic synthesizers, such as the ARP Odyssey and Formanta Polivoks built in the 1970s and 1980s respectively, have a capability to independently play two pitches at a time. These synthesizers have at least two oscillators that are separately controllable, and a duophonic keyboard that can generate two control voltage signals for the lowest- and highest-note. When two or more keys are pressed simultaneously, the lowest- and highest-note will be heard. When only one key is pressed, both oscillators are assigned to one note, possibly with a more complex sound.
Paraphonic synthesizers, such as the Roland RS-202 string machine or Korg Poly-800, were designed to play multiple pitches at the same time by using multiple oscillators, but with a common filter and/or amplifier circuit shared among all the voices. The result is a synthesizer that can play chords, provided all the notes start and end at the same time (homophony). For example, playing a new note on top of notes already held might retrigger the volume envelope for the entire sound. Monophonic synthesizers with more than one oscillator (such as the ARP 2600) can often be patched to behave in a paraphonic manner, allowing for each oscillator to play an independent pitch which is then routed through a common VCF and VCA.
The earliest polyphonic synthesizers were built in the late-1930s, but the concept did not become popular until the mid-1970s. Harald Bode's Warbo Formant Orguel, developed in 1937, was an archetype of a voice allocation polyphonic synthesizer. Novachord by Hammond Organ Company, released in 1939, is a forefather product of frequency divider organs and polyphonic synthesizer. It uses octave divider technology to generate polyphony, and about 1,000 Novachords were manufactured until 1942.
Using an octave divider a synthesizer needs only 12 oscillators - one for each note in the musical scale. The additional notes are generated by dividing down the outputs of these oscillators. To produce a note one octave lower, the frequency of the oscillator is divided by two. Polyphony is achieved so long as only one of each note in the scale is played simultaneously.
|Hammond Novachord (1939)
A forefather of octave divider synth and electronic organs.
|Moog Polymoog (1975)
Octave divider technology similar to Novachord was used.
|Korg PE-1000 (1976)
Polyphonic ensemble keyboard consists with one synth per key (totally 60 synthesizers), based on octave divider
|Korg PS-3300 (1977)|
Patchable polyphonic synthesizer consists with three synths per key (totally 144 synthesizers), based on octave divider.
In the early-to-mid-1970s, the voice allocation technology with digital keyboard scanning was independently developed by several engineers and musical instrument manufacturers, including Yamaha, E-mu Systems, and Armand Pascetta (Electro Group). The Oberheim Polyphonic Synthesizer and Sequential Circuits Prophet-5 were both developed in collaboration with E-mu System.
|Yamaha GX-1 (1973/1975)
Voice allocation technology was used to assign the limited 8-voices per manual into the notes. It was succeeded by the portable Yamaha CS-80 (1976), which was successful and became one of the most popular polyphonic analog synths.
|Live Electronic Orchestra (LEO) by Don Lewis (1977)
LEO used Armand Pascetta's polyphonic keyboard (c. 1975) to control the multiple synthesizers.
|Sequential Circuits Prophet-5 (1978)|
One notable early polyphonic synthesizer, the Prophet 5 released in 1978, had five-voice polyphony. Another notable polyphonic synth, the Yamaha CS-80 released in 1976, had eight-voice polyphony, as did the Yamaha GX-1 with total 18 voice polyphony, released in 1973. Six-voice polyphony was standard by the mid-1980s. With the advent of digital synthesizers, 16-voice polyphony became standard by the late 1980s. 64-voice polyphony was common by the mid-1990s and 128-note polyphony arrived shortly after. There are several reasons for providing such large numbers of simultaneous notes:
Synthesizers generally use oscillators to generate the electric signal that forms the basis of the sound, often with a keyboard to trigger the oscillators. However, multiple oscillators working independently are a considerable challenge to implement. To double the polyphony, not only must the number of oscillators be doubled but the electronics must also function as a switch connecting keys to free oscillators instantaneously, implementing an algorithm that decides which notes are turned off if the maximum number of notes is already sounding when an additional key is pressed. There are several ways to implement this:
Modern synthesizers and samplers may use additional, multiple, or user-configurable criteria to decide which notes sound.
Almost all classical keyboard instruments are polyphonic. Examples include the piano, harpsichord, organ and clavichord. These instruments feature a complete sound-generating mechanism for each key in the keybed (e.g., a piano has a string and hammer for every key, and an organ has at least one pipe for each key.) When any key is pressed, the note corresponding to that key will be heard as the mechanism is activated.
Some clavichords do not have a string for each key. Instead, they will have a single string which will be fretted by several different keys. Out of the keys that share a single string, only one may sound at a time.
With a few exceptions, electric organs consist of two parts: an audio-generating system and a mixing system. The audio-generating system may be electronic (consisting of oscillators and octave dividers) or it may be electromechanical (consisting of tonewheels and pickups), and it sends a large number of audio outputs to a mixer. The stops or drawbars on the organ modify the signal sent from the audio-generating system, and the keyboard switches the mixer's channels on and off. Those channels which are switched on are heard as notes corresponding to the depressed keys.
In classical music, a definition of polyphony does not only mean just playing multiple notes at once but an ability to make audiences perceive multiple lines of independent melodies. Playing multiple notes as a whole, such as a rhythm from a chord pattern, is not polyphony but homophony.
A classical violin has multiple strings and indeed is polyphonic but harder for some beginners to play multiple strings by bowing. One needs to control the pressure, speed and angle well for one note before having an ability to play the multiple notes at acceptable quality expected by the composers.
Therefore, even though the violin family of instruments are misleadingly considered (when bowing) by general untrained musicians to be primarily monophonic, it can be polyphony by both pizzicato (plucking) and bowing techniques for standard trained soloists and orchestra players. The evidence can be seen in compositions since the 17th century such as Bach sonatas and partitas for unaccompaniment solo violin.
Multiphonics can be used with many regular wind instruments to produce two or more notes at once, although this is considered an extended technique. Explicitly polyphonic wind instruments are relatively rare, but do exist.
The standard harmonica can easily produce several notes at once.
Multichambered ocarinas are manufactured in a number of varieties, including double, triple, and quadruple ocarinas, which use multiple chambers to extend the ocarina's otherwise limited range, but also enable the musician to play more than one note simultaneously. Harmonic ocarinas are specifically designed for polyphony, and in these instruments the range of the chambers usually overlap to some extent (typically at the unison, third, fourth, fifth, seventh or octave). Cross-fingering enables a single chamber to span an entire octave or more.
Recorders can also be doubled for polyphony. There are two types of double recorder; drone and polyphonic. In the drone type, one tube is tuned exactly like a regular recorder with a range of approximately two octaves, and the other tube is a drone and plays the tonic note of the scale. The polyphonic recorder has two tubes with a range of one major sixth. With overblowing, some notes can be played an octave higher, but it is not possible to achieve the range of an entire octave in one tube with these instruments.
... Introduced in 1975, the GX-1 was ... In 1973, Yamaha completed development work on a prototype codenamed the GX-707. Based on cluster voltage control, this instrument could be regarded as the predecessor of the Electone GX-1. ... As the flagship model in the Electone lineup, however, this prototype was conceived of as a theatre model for use on the concert stage. With a console weighing in excess of 300 kg and a separate board required for editing tones, it was not well suited for sale to the general public, and to this day is still considered a niche instrument.", "Why digital technology in an analog synth? ... It was thus clear that new control technology would be required in order to use a limited number of circuits in a more effective manner. ... This type of device was known as a key assigner, and it can rightly be called the predecessor of today's dynamic voice allocation (DVA) technology. Back in the early seventies, when tone generators still relied on analog technology, digital circuitry was already being put to use in these key assigners.
... I'm not the kind of circuit design expert that Bob Moog was. ... When I did Oberheim, I didn't consider myself a great circuit guy, so I had help. In one case part of the Oberheim module was designed by an engineer at ARP, and another was designed by an engineer at E-mu, by the guy who started E-mu ...", "Oberheim Four-Voice polyphonic synthesizer. ... in January 1975, I got the idea to put four or eight of these [little synthesizer] modules together with just a simple digital keyboard and have the first polyphonic synthesizer. And so I designed this module, it was already in existence when I made this decision, so it took me about six weeks to design this machine. ... a few months later showed it at the NAMM show, and the Oberheim synthesizer world was born.
There were two parts that led to the development of the Prophet-5. One was I already had a background in microprocessors, so I knew how they worked. In my day job, I was using microprocessors, so it was a real obvious thing to me to use a microprocessor to make a programmable polyphonic synth. The other thing is, we knew the people from E-mu systems, ... I had heard that they were involved with developing a new chip set where they had an oscillator integrated circuit, they had a filter circuit, and they had an envelope and a VCA. ...
Description: Custom-built modular synthesizer system consisting of a three-manual controller with a pedalboard, ... Produced: Schematics completed December 20, 1974, assembly began in '75, and system finished in May '77. ... Manufacture: Don Lewis. Pre-MIDI 4-channel polyphonic keyboard designed by Armand Pascetta. Richard Bates served as chief engineer; ... The "Pascetta parts" of LEO -- four Oberheim SEMs and two ARP 2600s controlled by Armand Pascetta's custom-designed keyboard ...'
CS80 was launched in 1976", "CS80 could almost be thought of as two polyphonic synths, because there are two independent 8-voice sections available.