Polyphony is a property of musical instruments, meaning they can play multiple notes simultaneously. Instruments featuring polyphony are said to be polyphonic.[citation needed] Instruments that are not capable of polyphony are monophonic.
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Most of early synthesizers were monophonic musical instruments which can play only one note at a time, and are often called monosynth as opposed to polysynth. For example, Minimoog has three oscillators which are settable in arbitrary intervals, but it can play only one note at a time (with a timbre consists of three pitches of fixed-intervals).
Duophonic synthesizers, such as the ARP Odyssey and Formanta Polivoks built in the 1970s, has a capability to play independent two pitches at a time. These synthesizers have (at least) two oscillators separately controllable, and duophonic keyboard that can generate two control voltage signals for lowest- and highest-note. When two or more keys are pressed simultaneously, lowest- and highest-note will be heard. When only one key is pressed, both oscillators are assigned to one note, and possibly more complex sound will be heard.
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.[1] Novachord by Hammond Organ Company, released in 1939, is a forefather product of octave divider synthesizer and electronic organs. It uses frequency divider technology to generate polyphony,[2] and about one thousand Novachords were manufactured until 1942.[3]
In the early 1970s, Allen Organ Company, E-mu Systems and Yamaha independently developed digital keyboard scanning technology, and the results were known as Oberheim 2/4/8-voices licensed by E-mu Systems [4] and Yamaha GX-1.
| 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). |
Korg PS-3300 (1977) Although it uses octave divider, it contains three synths per key. |
| Yamaha GX1 (1973) Voice allocation technology was used to assign limited 8-voices per manual into notes. |
E-mu Modular System (1972) In 1974, E-mu released polyphonic keyboards for it.[4] |
Oberheim 4voice (1975) Polyphonic technology was licensed by E-mu Systems.[4] |
Sequential Circuites Prophet-5 (1977) is one of the most popular polyphonic synth featuring patch memories, also used E-mu's technology.[4] |
One notable early polyphonic synthesizer was the Sequential Circuits Prophet 5, which was released in 1977 and had five-voice polyphony. Six-voice polyphony was standard by the middle 1980s. With the advent of digital synthesizers, 16-voice polyphony became standard by the late 1980s. 64-voice polyphony was common by the middle 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 and/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 mechamism 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.
The electric piano and clavinet rely on the same principles to achieve polyphonic operation. An electric piano has a separate hammer, vibrating metal tine and electrical pickup for each key.
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.
Stringed instruments may be polyphonic if they have a separate string for each note to be played. The harp has a large number of strings, one for each note in the scale, so it is polyphonic; The guitar has multiple strings and is usually chorded and not played one string at a time, so it is polyphonic; The violin has multiple strings, but usually only one is bowed at a time, so the violin family of instruments are considered to be monophonic.
Some eastern instruments include strings which are fretted and plucked like those on a guitar, plus secondary strings which resonate and provide reverberation on a few key notes. This is technically not polyphony, but it can be used to simulate polyphony.
The electric guitar, just like the classical guitar, is polyphonic, as are the various guitar derivatives that have turned up (including the harpejji and the Chapman stick).
Although polyphonic wind instruments are relatively rare, they do exist. 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. 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; the drone type and the polyphonic type. 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.