How Do Synthesizers Work? Definition, History, and Role in Producing Music

A synthesizer is an electronic instrument that uses some form of digital or analog processing to produce audible sound. As their name might suggest, most synthesizers seek to artificially reproduce (or synthesize) the sounds of acoustic instruments like those listed above.

Synthesizers that emulate acoustic instruments do not generate sounds the same way that an acoustic instrument does. For instance, many electronic synthesizers contain settings labeled “piano,” which means that setting will produce a sound that evokes an 88-key classical piano but that is actually produced by a series of electronic tone generators. The physical activity that makes a piano produce sound—a felted hammer striking tuned strings—never occurs with the synthesizer.

Today’s synthesizers are most commonly oriented around personal computers, but their forebears took on many forms. The earliest examples of audio synthesizers include:

• The Dynamophone, patented by Thaddeus Cahill in 1897
• The theremin, a contact-free synthesizer comprised of electronic oscillators, that was patented by Léon Theremin in 1928
• The RCA Electronic Music Synthesizer Mark I, which was released in 1956

A major breakthrough in analog synthesizer technology was made by inventor Robert Moog, whose eponymous modular synthesizers produced a wide array of sounds via sine waves, saw waves, square waves, and low-frequency oscillators. Moog’s initial inventions could easily fill an entire room, but with the advent of the Minimoog, his technology became available for home consumers.

Digital synthesizers came into play in the 1970s, and by the 1980s they dominated pop music. A particularly ubiquitous model was the Yamaha DX7, which featured a piano-style keyboard and was comparatively lightweight compared to its predecessors (although extremely heavy by modern keyboard standards).

Traditional synthesizers use electronic oscillators to produce sounds.

• Both digital oscillators and analog voltage-controlled oscillators (VCOs) are used by today’s electronic musicians. Via these oscillators, musicians can produce sounds by either additive synthesis—where multiple sine waves, square waves, and sawtooth waves are stacked upon each other—or by subtractive synthesis — where a series of filters remove frequencies from these sound waves.
• A filter is set to literally filter out certain frequencies of sound. For instance, a low-pass filter allows low frequencies to pass through while blocking higher frequencies. A high-pass filter does the opposite. Filters can be set for anywhere along the audio spectrum, blocking one set of frequencies while allowing others to pass through. In many ways, a filter is just an extreme variant of an equalizer (EQ) effect.

A low-frequency oscillator (LFO) generates electronic signals on the low end of human hearing, typically around 20 Hz. These devices are useful for producing rhythmic effects like tremolo, which rapidly varies the volume of a sound wave. Volume can also be manipulated by envelope filters, which control the attack, decay, sustain, and release of an audio signal.

• The attack is the amount of time it takes for an audio signal to reach peak volume
• Decay is the amount of time it takes for the signal to go from its peak volume to a lower level known as its sustain volume
• Sustain is the volume level the sound remains at until the key is released
• The release is the amount of time it takes for the sound to go from its sustain volume to absolute silence

In today’s popular music, synthesizers dominate the instrumental palette. Thanks to comprehensive keyboard synthesizers from the likes of Roland, Korg, Yamaha, and others, electronic musical instruments are often found on stage at major concerts, as they are able to produce sounds that were once solely reserved for traditional instruments like guitar and drums.

Meanwhile, massive software libraries by the likes of Ableton, Native Instruments, EastWest, Fruity Loops, Logic, and many others have made personal computers into synthesizers for both the studio and the stage.

Genres with particularly heavy synth components include Top 40, house, club, EDM, hip hop, and trance. In addition, genres that are more commonly associated with traditional instruments, such as rock, country, and R&B now also make ample use of synthesizers. Even classical and jazz artists have gotten into the synthesizer game, although those genres remain dominated by acoustic instruments.

Whether it’s an 88-key polyphonic synthesizer, a 61-key monophonic synthesizer, or a computer loaded up with soft synths, new instruments are constantly appearing that further engrain electronic sounds into the popular consciousness. The power of synthetic audio has helped define twenty-first-century music and it remains a key element within countless genres.

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