A synthesizer (also called a synthesiser or synth) is an electronic musical instrument that produces sound. Synthesizers create sounds by making waveforms using methods like subtractive synthesis, additive synthesis, and frequency modulation synthesis. These sounds can be changed using parts such as filters, which reduce or increase certain sounds; envelopes, which control how notes start and end; and low-frequency oscillators, which change features like pitch, volume, or sound quality. Synthesizers are usually played with keyboards or controlled by software, sequencers, or other instruments. They can connect to other equipment using MIDI.

Synthesizer-like instruments first appeared in the United States in the middle of the 20th century. One early example was the RCA Mark II, which used punch cards and many vacuum tubes. The Moog synthesizer, created by Robert Moog and sold in 1964, introduced important ideas such as voltage-controlled oscillators, envelopes, noise generators, filters, and sequencers. In 1970, the smaller and less expensive Minimoog became the first self-contained synthesizer with built-in keyboards, unlike the larger modular synthesizers before it.

In 1978, Sequential Circuits released the Prophet-5, which used microprocessors to let users save sounds for the first time. MIDI, a standard way to connect electronic instruments, was developed in 1982 and is still widely used. The Yamaha DX7, released in 1983, was very popular and helped spread the use of digital synthesis. Today, software synthesizers can run as plug-ins or be built into microchips. In the 21st century, analog synthesizers became popular again because they became cheaper to make.

At first, synthesizers were seen as unusual and were used mainly by artists in the 1960s psychedelic and countercultural movements. However, they were not seen as commercially valuable. The album Switched-On Bach (1968), which used a synthesizer to arrange music by Bach, helped bring synthesizers into the mainstream. They were later used by electronic, pop, and rock musicians in the 1960s and 1970s. Synthesizers became common in 1980s music. Sampling, introduced with the Fairlight synthesizer in 1979, influenced genres like electronic and hip hop music. Today, synthesizers are used in nearly every music style and are considered one of the most important instruments in the music industry. According to Fact in 2016, "The synthesizer is as important, and as ubiquitous, in modern music today as the human voice."

History

As electricity became more widely used, the early 20th century saw the creation of electronic musical instruments such as the Telharmonium, Trautonium, ondes Martenot, and theremin. In the late 1930s, the Hammond Organ Company built the Novachord, a large instrument that used 72 amplifiers and 146 vacuum tubes to control sound. In 1948, the Canadian engineer Hugh Le Caine completed the electronic sackbut, an early version of a synthesizer that used a keyboard to control features like vibrato, glissando, and attack.

In 1957, Harry Olson and Herbert Belar completed the RCA Mark II Sound Synthesizer at RCA laboratories in Princeton, New Jersey. This instrument used punched paper tape to control an analog synthesizer with 750 vacuum tubes. It was later used mostly by Milton Babbitt, a composer at Princeton University.

The book Analog Days describes the early years of the synthesizer as the period from 1964 to the mid-1970s, beginning with the introduction of the Moog synthesizer, designed by Robert Moog. The Moog used separate parts connected by cables to create, shape, or control sound. Moog developed a system to control pitch using voltage, called a voltage-controlled oscillator. This, along with other components like filters and sequencers, became standard in synthesizers.

Around the same time, the American engineer Don Buchla created the Buchla Modular Electronic Music System. Instead of a keyboard, Buchla’s system used touchplates that changed based on finger position and pressure. However, the Moog’s keyboard made it easier for musicians to use, and keyboards became the standard for controlling synthesizers. Moog and Buchla avoided using the word “synthesizer” at first because it was linked to the RCA synthesizer, but by the 1970s, the term became common.

In 1970, Moog released the Minimoog, a smaller and cheaper synthesizer sold in music stores. It was the first synthesizer designed for live performances and helped establish synthesizers as self-contained instruments with built-in keyboards. In the early 1970s, the British composer Ken Freeman created the first string synthesizer, which imitated string instruments.

After synthesizers began selling in stores in 1971, other companies like ARP in the U.S. and EMS in the U.K. started making synthesizers. ARP made models like the ARP 2600, which could be carried in a case and had built-in speakers, and the Odyssey, a competitor to the Minimoog. The less expensive EMS synthesizers were used by European musicians like Brian Eno and Pink Floyd. Designs for synthesizers also appeared in electronics magazines, such as a 1973 article in Practical Electronics. By the mid-1970s, ARP was the largest synthesizer maker, though it closed in 1981.

Early synthesizers could only play one note at a time. Some of the first polyphonic synthesizers (ones that could play multiple notes) were made by Tom Oberheim, such as the OB-X (1979). In 1978, Sequential Circuits released the Prophet-5, the first fully programmable polyphonic synthesizer. Unlike earlier models, the Prophet-5 used microprocessors to save sound settings, making it easier to recreate sounds consistently. This shift helped move synthesizers from making unpredictable sounds to offering familiar, standard sounds.

The synthesizer market grew quickly in the 1980s. In 1982, MIDI was introduced as a standard way to connect electronic instruments, and it is still used today. In 1979, the Fairlight CMI, a sampling synthesizer that could record and play back sounds, was released. Though expensive, it was used by famous musicians like Kate Bush and Peter Gabriel. Competition from other samplers, such as the E-mu Emulator (1981) and the Akai S-series (1985), led to better technology and lower prices.

In 1983, Yamaha released the DX7, the first widely successful digital synthesizer. It used a method called frequency modulation (FM) synthesis, developed by John Chowning at Stanford University. The DX7 had a unique, cold sound compared to the warm tones of analog synthesizers. It sold over 100,000 units and remains one of the best-selling synthesizers.

Digital synthesizers often had preset sounds that mimicked real instruments, controlled by menus and buttons. The Synclavier, which used FM technology from Yamaha, offered features like 16-bit sampling and digital recording but cost $13,000, limiting its use to studios and wealthy artists. The Roland D-50 (1987) combined Roland’s linear arithmetic algorithm with samples and was the first synthesizer with built-in effects like reverb and chorus. In 1988, Korg released the M1, a digital synthesizer that sold over 250,000 units and is still the best-selling synthesizer. The rise of digital synthesizers led to less interest in analog models in the 1990s.

In 1997, software synthesizers like ReBirth and Reality were released, allowing users to play them in real time via MIDI. In 1999, an update to Cubase let users run software instruments as plug-ins, leading to more software synthesizers. In 2000, Propellerhead released Reason, a virtual studio tool with many familiar synthesizer features.

Interest in modular and patchable synthesizers returned in the late 1990s. In the 2000s, older analog synthesizers became popular again, sometimes selling for much more than their original prices. In the 2010s, companies like Moog, Korg, Arturia, and Dave Smith Instruments introduced new, affordable analog synthesizers. This renewed interest is due to the appeal of organic, imperfect sounds and simpler designs, as well as modern manufacturing techniques that make analog synthesizers cheaper to produce.

Impact

Early synthesizers were seen as experimental, valued by the 1960s psychedelic and counter-cultural music scenes for their ability to create new sounds. However, they were not thought to have much commercial value at first. The 1968 album Switched-On Bach, which featured Johann Bach’s music played on a Moog synthesizer by Wendy Carlos, showed that synthesizers could be more than just noise-making devices. This helped bring synthesizers into the mainstream. Some people debated whether synthesizers were appropriate for baroque music, and according to The Guardian, they were quickly avoided by serious classical musicians.

Today, synthesizers are one of the most important instruments in the music industry, used in nearly every music genre. Authors of Analog Days describe synthesizers as "the only innovation that can stand alongside the electric guitar as a great new instrument of the age of electricity." Both the synthesizer and the electric guitar led to new types of music and had widespread popularity. According to Fact in 2016, "The synthesizer is as important, and as common, in modern music today as the human voice."

The Moog synthesizer was used by 1960s rock bands such as the Doors, the Grateful Dead, the Rolling Stones, the Beatles, and Keith Emerson. Emerson was the first major rock musician to perform with the Moog, and it became a key part of his performances. This helped his band, Emerson, Lake & Palmer, become famous worldwide. Analog Days notes that musicians like Emerson "did for the keyboard what Jimi Hendrix did for the guitar." String synthesizers were also used by 1970s progressive rock bands, including Camel, Caravan, Electric Light Orchestra, Gentle Giant, and Renaissance.

The portable Minimoog, released in 1970, was much smaller than earlier modular synthesizers. This made synthesizers easier to use in live performances. Early synthesizers could only play one note at a time, which made them useful for basslines, leads, and solos. However, with the development of polyphonic synthesizers in the 1970s and 1980s, keyboards in rock music were used more for background sounds and fills rather than for solos. Queen’s 1970s albums stated that no synthesizers were used, but they included them in their 1980 album The Game.

The Minimoog became popular in African-American music, especially in the work of Stevie Wonder, and in jazz, such as the music of Sun Ra. In the late 1970s and early 1980s, the Minimoog was widely used in the disco genre by artists like ABBA and Giorgio Moroder. Sampling, introduced with the Fairlight synthesizer in 1979, influenced all music genres and played a major role in the development of electronic and hip-hop music.

In the 1970s, electronic music composers like Jean Michel Jarre and Isao Tomita created successful instrumental albums using synthesizers. This helped the synth-pop genre develop from the late 1970s to the early 1980s. German krautrock bands such as Kraftwerk and Tangerine Dream, British artists like John Foxx, Gary Numan, and David Bowie, African-American musicians like George Clinton and Zapp, and Japanese acts such as Yellow Magic Orchestra and Kitaro were important in shaping the genre.

The Roland TB-303, a sequencer-based synthesizer released in 1981, along with the Roland TR-808 and TR-909 drum machines, became the foundation of electronic dance music genres like house and techno. These machines were often used by producers who bought second-hand units later in the 1980s. Analog Days connects the origins of synthesizers in 1960s psychedelic music to the rave culture of the 1980s and the club scenes of the 1990s and 2000s.

Gary Numan’s 1979 songs "Are 'Friends' Electric?" and "Cars" heavily used synthesizers. OMD’s 1980 song "Enola Gay" featured electronic percussion and a synthesized melody. Soft Cell used a synthesized melody in their 1981 hit "Tainted Love." Nick Rhodes, the keyboardist of Duran Duran, used synthesizers like the Roland Jupiter-4 and Jupiter-8. Chart-topping songs include Depeche Mode’s "Just Can’t Get Enough" (1981), the Human League’s "Don’t You Want Me," and works by Ultravox.

In the 1980s, digital synthesizers became common in pop music. The Yamaha DX7, released in 1983, was widely used in pop songs by artists like A-ha, Kenny Loggins, and Kool & the Gang. Its "E PIANO 1" preset became famous, especially in power ballads, and was used by artists such as Whitney Houston, Chicago, Prince, Phil Collins, Luther Vandross, Billy Ocean, and Celine Dion. Korg M1 presets were used in 1990s house music, starting with Madonna’s 1990 single "Vogue."

Synthesizers are often used in film and television soundtracks. In 1969, Mort Garson used a Moog synthesizer to create the soundtrack for the Apollo 11 moonwalk, linking electronic music to space in American culture. ARP synthesizers were used to make sound effects for the 1977 films Close Encounters of the Third Kind and Star Wars, including the voice of the robot R2-D2.

In the 1970s and 1980s, synthesizers were used in movie scores for thrillers and horror films such as A Clockwork Orange (1971), Apocalypse Now (1979), The Fog (1980), and Manhunter (1986). Brad Fiedel used a Prophet synthesizer for the Terminator (1984) soundtrack, and John Carpenter used synthesizers extensively in his films. Synthesizers were also used for themes in TV shows like Knight Rider (1982), Twin Peaks (1990), and Stranger Things (2016).

When a rerecorded version of the song "Video Killed the Radio Star" was played on Top of the Pops, a member of the Musicians’ Union said, "If I think you’re making string sounds out of a synthesizer, I’m going to have you. 'Video Killed the Radio Star' is putting musicians out of business."

The rise of synthesizers caused major changes in the music industry, similar to the introduction of sound in films in the 1920s, which led to job losses for live musicians who accompanied silent films. Synthesizers could imitate instruments like strings and horns, threatening the work of session musicians by allowing one person to create the sounds of an entire orchestra. At one time, the Moog

Sound synthesis

Synthesizers create sound using different methods of analog and digital synthesis.

• In subtractive synthesis, oscillators produce complex waveforms, which are then changed by filters that remove or increase certain frequencies. Subtractive synthesis sounds rich and warm.
• In additive synthesis, many waveforms, often sine waves, are combined to form a single sound.
• In frequency modulation (FM) synthesis, also called phase modulation, a carrier wave is changed using the frequency of a modulator wave. This process can repeat, with each modulator affecting the next. FM synthesis sounds harsh, glassy, and chilly.
• Phase distortion synthesis, used in Casio CZ synthesizers, works similarly to FM synthesis.
• In wavetable synthesis, synthesizers smoothly change between digital versions of different waveforms, altering the sound's shape and quality.
• In sample-based synthesis, recorded sounds (digital copies of real sounds) are played back and modified using tools like filters, envelopes, and LFOs.
• In vector synthesis, developed by the Prophet VS, users blend different sounds using controls like joysticks, envelopes, and LFOs.
• In granular synthesis, an audio sample is divided into small pieces, usually between one hundredth and one tenth of a second long, which are then recombined and played back.
• In physical modeling synthesis, a mathematical model that represents a real-world sound source is created.

Components

Oscillators create waveforms, such as sawtooth, sine, or pulse waves, that produce different types of sounds.

Voltage-controlled amplifiers (VCAs) control the volume or strength of an audio signal. VCAs can be adjusted by other components, like LFOs and envelopes. A VCA acts as a preamplifier that increases the strength of an electronic signal before sending it to a power amplifier. It also allows the signal's volume to be controlled using an attenuator. The strength of the VCA is changed by a control voltage (CV) from sources such as an envelope generator, an LFO, a keyboard, or another device.

Envelopes control how sounds change over time. They can adjust parameters like volume, filters, or pitch. The most common type of envelope is the ADSR envelope:

• Attack is the time it takes for the sound to rise from silence to its loudest level when a note is played.
• Decay is the time it takes for the sound to decrease from the loudest level to a steady level.
• Sustain is the level the sound remains at during the main part of the note, until the key is released.
• Release is the time it takes for the sound to fade from the steady level to silence after the key is released.

Low-frequency oscillators (LFOs) create waveforms that change parameters, such as the pitch of oscillators, to produce effects like vibrato.

Filters remove specific frequencies from an audio signal, similar to how equalization adjusts sound. They usually have controls to set the frequency at which sound is reduced and to add resonance. Common types include low-pass filters, which remove high frequencies above a set point, and high-pass filters, which remove low frequencies below a set point. Filters can be adjusted using envelopes or LFOs.

Arpeggiators take musical chords and play them as arpeggios. They often have controls for speed, range, and mode (how the notes are arranged).

Synthesizers are often controlled using electronic or digital keyboards, or MIDI controller keyboards. These may be built into the synthesizer or connected via cables, USB, or MIDI. Keyboards can detect how hard a key is pressed (velocity sensitivity) and how much pressure is applied after the key is pressed (aftertouch), allowing for more control over the sound. Other controllers include ribbon controllers that track finger movement across a sensitive surface, wind controllers that work like woodwind instruments, motion-sensitive controllers similar to video game devices, electronic drum pads that mimic drum kits, touchplates that respond to finger position and pressure, controllers for microtonal tunings, touchscreen devices like tablets and smartphones, and fingerpads.

Clones

Synthesizer clones are copies of older synthesizers made without permission, often sold as cheaper versions of well-known musical equipment. These clones can be found as real instruments or as software programs. Companies like Arturia and Native Instruments sell software versions of these clones. Behringer makes devices that copy the designs of famous synthesizers, such as the Minimoog, Pro-One, and TB-303, as well as drum machines like the TR-808. Other examples of synthesizer clones include the MiniMOD (a set of Eurorack modules inspired by the Minimoog), the Intellijel Atlantis (based on the SH-101), and the x0x Heart (based on the TB-303).

Making copies of older hardware is allowed when the patents for the original designs are no longer valid. In 1997, Mackie lost a legal case against Behringer because U.S. copyright laws did not protect the designs of their circuit boards.