A synthesizer (often abbreviated "synth") is an electronic instrument capable of producing sounds by generating electrical signals of different frequencies. These electrical signals are played through a loudspeaker or set of headphones. Synthesizers can usually produce a wide range of sounds, which may either imitate other instruments ("imitative synthesis") or generate new timbres.
Synthesizers use a number of different technologies or programmed algorithms, each with their own strengths and weaknesses. Among the most popular waveform synthesis techniques are subtractive synthesis, additive synthesis, wavetable synthesis, frequency modulation synthesis, phase distortion synthesis, physical modeling synthesis and sample-based synthesis. Other sound synthesis methods, like subharmonic synthesis or granular synthesis, are not commonly found in hardware music synthesizers.
Synthesizers are often controlled with a piano-style keyboard, leading such instruments to be referred to simply as "keyboards". Several other forms of controller have been devised to resemble violins, guitars (see guitar synthesizer) and wind-instruments. Synthesizers without controllers are often called "modules", and they can be controlled using MIDI or CV/Gate methods.
The first electric synthesizer was invented in 1876 by Elisha Gray, who is best known for his development of a telephone prototype. In 1920s, Arseny Avraamov developed various systems of graphic sonic art. The Hammond Novachord was an early but unsuccessful harbinger of synth technology in the 1930s-40s. In 1949, Japanese composer Minao Shibata discussed the concept of "a musical instrument with very high performance" that can "synthesize any kind of sound waves" and is "operated very easily," predicting that with such an instrument, "the music scene will be changed drastically." In 1958, USSR's engineer Yevgeny Murzin made the very first synthesizer, called the ANS. Although RCA had produced a machine called the Electronic Music Synthesizer in 1951–52, it would be better classified as a "composition machine", because the sounds were not produced in real time. RCA later developed the RCA Mark II Sound Synthesizer at the Columbia-Princeton Electronic Music Center, the first programmable synthesizer, which was inaugurated in 1957. Prominent composers such as Vladimir Ussachevsky, Otto Luening, Milton Babbitt, Halim El-Dabh, Bülent Arel, Charles Wuorinen and Mario Davidovsky used the RCA Synthesizer extensively in various compositions.
Robert Moog introduced the first commercially available modern synthesizer in 1964. In the 1970s the development of miniaturized solid-state components allowed synthesizers to become self-contained, portable instruments. By the early 1980s companies were selling compact, modestly priced synthesizers to the public. This, along with the development of Musical Instrument Digital Interface (MIDI), made it easier to integrate and synchronize synthesizers and other electronic instruments for use in musical composition. In the 1990s, synthesizers began to appear as computer software, known as software synthesizers.
The synthesizer had a considerable impact on 20th century music. Micky Dolenz of The Monkees bought one of the first Moog synthesizers. The band was the first to release an album featuring a Moog with Pisces, Aquarius, Capricorn & Jones Ltd. in 1967. It reached #1 on the charts. A few months later, both the Rolling Stones' "2000 Light Years from Home" and the title track of the Doors' 1967 album Strange Days would also feature a Moog, played by Brian Jones and Paul Beaver respectively. Wendy Carlos's Switched-On Bach (1968), recorded using Moog synthesizers, also influenced numerous musicians of that era and is one of the most popular recordings of classical music ever made, alongside the records of Isao Tomita (particularly Snowflakes are Dancing in 1974), who in the early 1970s utilized synthesizers to create new artificial sounds (rather than simply mimicking real instruments) and made significant advances in analog synthesizer programming.
The sound of the Moog also reached the mass market with Simon and Garfunkel's Bookends in 1968 and The Beatles' Abbey Road the following year, and hundreds of other popular recordings subsequently used synthesizers. Electronic music albums by Beaver and Krause, Tonto's Expanding Head Band, The United States of America and White Noise reached a sizeable cult audience and progressive rock musicians such as Richard Wright of Pink Floyd and Rick Wakeman of Yes were soon using the new portable synthesizers extensively. Other early users included Emerson, Lake & Palmer's Keith Emerson, Pete Townshend and The Crazy World of Arthur Brown's Vincent Crane.
During the 1970s, Jean Michel Jarre, Larry Fast and Vangelis released successful electronic instrumental albums. The emergence of Synthpop, a sub-genre of New Wave, in the late 1970s can be largely credited to synthesizer technology. The ground-breaking work of all-electronic German bands such as Kraftwerk and Tangerine Dream, via David Bowie during his Berlin period (1976–77), as well as the pioneering work of the Japanese Yellow Magic Orchestra and British Gary Numan, were crucial in the development of the genre. Nick Rhodes, keyboardist of Duran Duran, used Roland Jupiter-4 and Jupiter-8 synthesizers. OMD's "Enola Gay" (1980) used a distinctive electronic percussion and synthesized melody. Soft Cell used a synthesized melody on their 1981 hit "Tainted Love". Other chart hits include Depeche Mode's "Just Can't Get Enough" (1981), and The Human League's "Don't You Want Me". English musician Gary Numan's 1979 hits "Are 'Friends' Electric?" and "Cars" used synthesizers heavily Other notable synthpop groups included Visage, Japan, Ultravox, Spandau Ballet, Culture Club, Eurythmics and Blancmange, and synthesizers became one of the most important instruments in the music industry. Other notable users include Giorgio Moroder, Howard Jones, Kitaro, Stevie Wonder, Peter Gabriel, Kate Bush, Frank Zappa, A Flock Of Seagulls and Devo.
Types of synthesisEdit
Additive synthesis builds sounds by adding together waveforms (which are usually harmonically related). An early analog example of an additive synthesizer is the Hammond organ. Additive synthesis is also the principle of Wavetable synthesis, which is used to implement real-time synthesis with minimum hardware, commonly used in low-end MIDI instruments such as educational keyboards, and low-end sound cards.
Subtractive synthesis is based on filtering harmonically rich waveforms. Due to its simplicity, it is the basis of early synthesizers such as the Moog synthesizer. Subtractive synthesizers use a simple acoustic model that assumes an instrument can be approximated by a simple signal generator (producing sawtooth waves, square waves, etc.) followed by a filter. The combination of simple modulation routings (such as pulse width modulation and oscillator sync), along with the physically unrealistic lowpass filters, is responsible for the "classic synthesizer" sound commonly associated with "analog synthesis" and often mistakenly used when referring to software synthesizers using subtractive synthesis.
FM synthesis (frequency modulation synthesis) is a process that usually involves the use of at least two signal generators (sine-wave oscillators, commonly referred to as "operators" in FM-only synthesizers) to create and modify a voice. Often, this is done through the analog or digital generation of a signal that modulates the tonal and amplitude characteristics of a base carrier signal. FM synthesis was pioneered by Chowning, who patented the idea and sold it to Yamaha. Unlike the exponential relationship between voltage-in-to-frequency-out and multiple waveforms in classical 1-volt-per-octave synthesizer oscillators, Chowning-style FM synthesis uses a linear voltage-in-to-frequency-out relationship and sine-wave oscillators. The resulting complex waveform may have many component frequencies, and there is no requirement that they all bear a harmonic relationship. Sophisticated FM synths such as the Yamaha DX-7 series can have 6 operators per voice; some synths with FM can also often use filters and variable amplifier types to alter the signal's characteristics into a sonic voice that either roughly imitates acoustic instruments or creates sounds that are unique. FM synthesis is especially valuable for metallic or clangorous noises such as bells, cymbals, or other percussion.
Phase distortion synthesis is a method implemented on Casio CZ synthesizers. It is quite similar to FM synthesis but avoids infringing on the Chowning FM patent.
Granular synthesis is a type of synthesis based on manipulating very small sample slices.
Physical modeling synthesis is the synthesis of sound by using a set of equations and algorithms to simulate a real instrument, or some other physical source of sound. This involves taking up models of components of musical objects and creating systems which define action, filters, envelopes and other parameters over time. The definition of such instruments is virtually limitless, as one can combine any given models available with any amount of sources of modulation in terms of pitch, frequency and contour. For example, the model of a violin with characteristics of a pedal steel guitar and perhaps the action of piano hammer. When an initial set of parameters is run through the physical simulation, the simulated sound is generated. Although physical modeling was not a new concept in acoustics and synthesis, it wasn't until the development of the Karplus-Strong algorithm and the increase in DSP power in the late 1980s that commercial implementations became feasible. Physical modeling on computers gets better and faster with higher processing.
Sample-based synthesis One of the easiest synthesis systems is to record a real instrument as a digitized waveform, and then play back its recordings at different speeds to produce different tones. This is the technique used in "sampling". Most samplers designate a part of the sample for each component of the ADSR envelope, and then repeat that section while changing the volume for that segment of the envelope. This lets the sampler have a persuasively different envelope using the same note.
Analysis/resynthesis is a form of synthesis that uses a series of bandpass filters or Fourier transforms to analyze the harmonic content of a sound. The resulting analysis data is then used in a second stage to resynthesize the sound using a band of oscillators. The vocoder, linear predictive coding, and some forms of speech synthesis are based on analysis/resynthesis.
Synthesizers generate sound through various analogue and digital techniques. Early synthesizers were analog hardware based but many modern synthesizers use a combination of DSP software and hardware or else are purely software-based (see softsynth). Digital synthesizers often emulate classic analog designs. Sound is controllable by the operator by means of circuits or virtual stages which may include:
- Electronic oscillators – create raw sounds with a timbre that depends upon the waveform generated. Voltage-controlled oscillators (VCOs) and digital oscillators may be used. Additive synthesis models sounds directly from pure sine waves, somewhat in the manner of an organ, while Frequency modulation and Phase distortion synthesis use one oscillator to modulate another. Subtractive synthesis depends upon filtering a harmonically rich oscillator waveform. Sample-based and Granular synthesis use one or more digitally recorded sounds in place of an oscillator.
- ADSR envelopes - provide envelope modulation to "shape" the volume or harmonic content of the produced note in the time domain with the principle parameters being attack, decay, sustain and release. These are used in most forms of synthesis. ADSR control is provided by Envelope Generators.
- Voltage-controlled filter (VCF) – "shape" the sound generated by the oscillators in the frequency domain, often under the control of an envelope or LFO. These are essential to subtractive synthesis.
- Low frequency oscillator (LFO) – an oscillator of adjustable frequency that can be used to modulate the sound rhythmically, for example to create tremolo or vibrato or to control a filter's operating frequency. LFOs are used in most forms of synthesis.
- Other sound processing effects such as ring modulators may be encountered.
- Voltage-controlled amplifier (VCA) – After the signal generated by one (or a mix of more Voltage-controlled oscillators), modified by filters and LFOs, and the signal's waveform is shaped (contoured) by an ADSR Envelope Generator, it then passes on to one or more voltage-controlled amplifiers (VCA) where. The VCA is a preamp that boosts (amplifies) the electronic signal before passing on to an external or built-in power amplifier, as well as a means to control its volume using an attenuator that affects a control voltage (coming from the keyboard or other trigger source), which affects the gain of the VCA.
When an acoustic musical instrument produces sound, the loudness and spectral content of the sound change over time in ways that vary from instrument to instrument. The "attack" and "decay" of a sound have a great effect on the instrument's sonic character. Sound synthesis techniques often employ an envelope generator that controls a sound's parameters at any point in its duration. Most often this is an "ADSR" (Attack Decay Sustain Release) envelope, which may be applied to overall amplitude control, filter frequency, etc. The envelope may be a discrete circuit or module, or implemented in software. The contour of an ADSR envelope is specified using four parameters:
- Attack time is the time taken for initial run-up of level from nil to peak, beginning when the key is first pressed.
- Decay time is the time taken for the subsequent run down from the attack level to the designated sustain level.
- Sustain level is the level during the main sequence of the sound's duration, until the key is released.
- Release time is the time taken for the level to decay from the sustain level to zero after the key is released.
An early implementation of ADSR can be found on the polyphonic 1938 Hammond Novachord (which predates the first Moog synthesizer by over 25 years). A seven-position rotary knob set ADS for all 72 notes; a footpedal controlled release. The ADSR was specified by Vladimir Ussachevsky (then head of the Columbia-Princeton Electronic Music Center) in 1965 while suggesting improvements for Bob Moog's pioneering work on synthesizers.
A common variation of the ADSR on some synthesizers, such as the Korg MS-20, was ADSHR (attack, decay, sustain, hold, release). By adding a "hold" parameter, the system allowed notes to be held at the sustain level for a fixed length of time before decaying. The General Instruments AY-3-8912 sound chip included a hold time parameter only; the sustain level was not programmable. Another common variation in the same vein is the AHDSR (attack, hold, decay, sustain, release) envelope, in which the "hold" parameter controls how long the envelope stays at full volume before entering the decay phase. Multiple attack, decay and release settings may be found on more sophisticated models.
Certain synthesizers also allow for a "delay" parameter, which would come before the "attack". Modern synthesizers like the Dave Smith Instruments Prophet '08 have DADSR (delay, attack, decay, sustain, release) envelopes. The delay setting determines how long there is silence after a note is hit, before the attack is heard. Some software synthesizers such as Image-Line's 3xOSC (included for free with their DAW FL Studio) have DAHDSR (delay, attack, hold, decay, sustain, release) envelopes.
Some electronic musical instruments allow the ADSR envelope to be inverted, which results in opposite behavior compared to the normal ADSR envelope. During the attack phase, the modulated sound parameter fades from the maximum amplitude to zero then, during the decay phase, rises to the value specified by the sustain parameter. After the key has been released the sound parameter rises from sustain amplitude back to maximum amplitude.
Electronic filters are particularly important in subtractive synthesis, being designed to pass some frequency regions through unattenuated while significantly attenuating ("subtracting") others. The low-pass filter is most frequently used, but band-pass filters, band-reject filters and high-pass filters are also sometimes available.
The filter may be controlled with a second ADSR envelope. An "envelope modulation" ("env mod") parameter on many synthesizers with filter envelopes determines how much the envelope affects the filter. If turned all the way down, the filter will produce a flat sound with no envelope. When turned up the envelope becomes more noticeable, expanding the minimum and maximum range of the filter.
A low-frequency oscillator (LFO) generates an electronic signal, usually below 20 Hz. LFO signals create a rhythmic pulse or sweep, often used to in vibrato, tremolo and other effects. In certain genres of electronic music, the LFO signal can control the cutoff frequency of a VCF to make a rhythmic wah-wah sound, or the signature dubstep wobble bass.
Modern synthesizers often look like small pianos, though with many additional knob and button controls. These are integrated controllers, where the sound synthesis electronics are integrated into the same package as the controller. However many early synthesizers were modular and keyboardless, while most modern synthesizers may be controlled via MIDI, allowing other means of playing such as;
- Fingerboards and touchpads
- Wind controllers
- Guitar-style interfaces
- Drum pads
- Music sequencers
- Non-contact interfaces akin to theremins
A ribbon controller or other violin-like user interface may be used to control synthesizer parameters. The concept dates to Maurice Martenot's 1928 Ondes Martenot (sliding a metal ring),, improved upon by Robert Moog (finger pressure). The ribbon controller has no moving parts. Instead, a finger pressed down and moved along it creates an electrical contact at some point along a pair of thin, flexible longitudinal strips whose electric potential varies from one end to the other. Older fingerboards used a long wire pressed to a resistive plate. A ribbon controller is similar to a touchpad, but a ribbon controller only registers linear motion. Although it may be used to operate any parameter that is affected by control voltages, a ribbon controller is most commonly associated with pitch bending.
Fingerboard-controlled instruments include the Hellertion, Heliophon, Trautonium, Electro-Theremin, Perspehone and the Swarmatron. A ribbon controller is used as an additional controller in the Yamaha CS-80 and CS-60, the Korg Prophecy and Korg Trinity series, the Kurzweil synthesizers, Moog synthesizers and others.
Rock musician Keith Emerson used it with the Moog modular synthesizer from 1970 onward. In the late 1980s, keyboards in the synth lab at Berklee College of Music were equipped with membrane thin ribbon style controllers that output MIDI. They functioned as MIDI managers, with their programming language printed on their surface, and as expression/performance tools. Designed by Jeff Tripp of Perfect Fretworks Co., they were known as Tripp Strips. Such ribbon controllers can serve as a main MIDI controller instead of a keyboard, as with the Continuum instrument.
Wind controllers are convenient for woodwind or brass players or emulation, being designed along the lines of those instruments. These may be analog or MIDI controllers or may include built-in synthesizers. In addition to a key arrangement the controller has breath-operated pressure transducers, and may have gate extractors, velocity sensors and bite sensors. Saxophone style controllers have included the Lyricon, and products by Yamaha, Akai and Casio. The mouthpieces range from alto clarinet to alto saxophone sizes. Melodica or recorder style controllers have included the Variophon, Martinetta, Tubophon and Joseph Zawinul's custom Korg Pepe. A Harmonica style interfaces was the Millionizer.
Trumpet style controllers have included products by Steiner, Yamaha, Morrison and Akai. A breath controller may be used as an adjunct to a conventional synthesizer. The Steiner Master's Touch and products which interface to the Yamaha Breath Controller are examples. Several controllers also provide breath-like articulation capabilities.
The Ondes Martenot control touche d’intensité, Theremin, footpedal and lightbeam controllers are examples. Envelope following systems, the most sophisticated being the vocoder, follow the power or amplitude of an audio signial, rather than using pressure transducers. Various companies make accordion controllers that use pressure transducers on bellows for articulation. More direct articulation using the vocal tract without breath is the Talk box.
Synthesizers became easier to integrate and synchronize with other electronic instruments and controllers with the introduction of Musical Instrument Digital Interface (MIDI) in 1983. First proposed in 1981 by engineer Dave Smith of Sequential Circuits, the MIDI standard was developed by a consortium now known as the MIDI Manufacturers Association. MIDI is an opto-isolated serial interface and communication protocol. It provides for the transmission from one device or instrument to another of real-time performance data. This data includes note events, commands for the selection of instrument presets (i.e. sounds, or programs or patches, previously stored in the instrument's memory), the control of performance-related parameters such as volume, effects levels and the like, as well as synchronization, transport control and other types of data. MIDI interfaces are now almost ubiquitous on music equipment and are commonly available on personal computers (PCs).
The General MIDI (GM) software standard was devised in 1991 to serve as a consistent way of describing a set of over 200 tones (including percussion) available to a PC for playback of musical scores. For the first time, a given MIDI preset would consistently produce an instrumental sound on any GM-conforming device. The Standard MIDI File (SMF) format (extension .mid) combined MIDI events with delta times - a form of time-stamping - and became a popular standard for exchange of music scores between computers. In the case of SMF playback using integrated synthesizers (as in computers and cell phones), the hardware component of the MIDI interface design is often unneeded.
Open Sound Control (OSC) is another music data specification designed for online networking. In contrast with MIDI, OSC allows thousands of synthesizers or computers to share music performance data over the Internet in realtime.
The bass synthesizer (or "bass synth") is used to create sounds in the bass range, from simulations of the electric bass or double bass to distorted, buzz-saw-like artificial bass sounds, by generating and combining signals of different frequencies. Bass synth patches may incorporate a range of sounds and tones, including wavetable-style, analog, and FM-style bass sounds, delay effects, distortion effects, envelope filters. A modern digital synthesizer uses a frequency synthesizer microprocessor component to generate signals of different frequencies. While most bass synths are controlled by electronic keyboards or pedalboards, some performers use an electric bass with MIDI pickups to trigger a bass synthesizer.
In the 1970s miniaturized solid-state components allowed self-contained, portable instruments such as the Moog Taurus, a 13-note pedal keyboard which was played by the feet. The Moog Taurus was used in live performances by a range of pop, rock, and blues-rock bands. An early use of bass synthesizer was in 1972, on a solo album by John Entwistle (the bassist for The Who), entitled Whistle Rymes. Stevie Wonder introduced synth bass to a wider audience in the early 1970s, notably on Superstition (1972) and Boogie On Reggae Woman (1974). In 1977 Parliament's funk single Flashlight used the bass synthesizer. Lou Reed, widely considered a pioneer of electric guitar textures, played bass synthesizer on "Families", from his 1979 album The Bells.
When the programmable music sequencer became widely available in the 1980s (e.g., the synclavier), bass synths were used to create highly syncopated rhythms and complex, rapid basslines. Bass synth patches incorporate a range of sounds and tones, including wavetable-style, analog, and FM-style bass sounds, delay effects, distortion effects, envelope filters. A particularly influential bass synthesizer was the Roland TB-303, featuring a built-in sequencer and released in late 1981, and which would later become synonymous with acid house music. One of the first to utilize it was Charanjit Singh in 1982, though it wouldn't be popularized until Phuture's "Acid Tracks" in 1987.
In the 2000s, several companies such as Boss and Akai produced bass synthesizer effect pedals for electric bass players, which simulate the sound of an analog or digital bass synth. With these devices, a bass guitar is used to generate synth bass sounds. The BOSS SYB-3 was one of the early bass synthesizer pedals. The SYB-3 reproduces sounds of analog synthesizers with Digital Signal Processing saw, square, and pulse synth waves and user-adjustable filter cutoff. The Akai bass synth pedal contains a four-oscillator synthesizer with user selectable parameters (attack, decay, envelope depth, dynamics, cutoff, resonance). Bass synthesizer software allows performers to use MIDI to integrate the bass sounds with other synthesizers or drum machines. Bass synthesizers often provide samples from vintage 1970s and 1980s bass synths. Some bass synths are built into an organ style pedalboard or button board.
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