What is a synthesizer?
A synthesizer is an instrument that produces sounds electronically. Unlike an acoustic instrument such as a piano, which uses vibrating strings to produce sound waves in the air, a synthesizer uses electronic signals that require an amplifier or loudspeaker to be heard. There is a wide range of synthesizers, both in form and in the kind of sounds they produce.
They can be used to imitate the sound of acoustic instruments, or they can produce tones, textures and effects that cannot be produced with traditional instruments. While there are many different types of synthesizers, they all have a few things in common: They generate an electronic audio signal, and they allow you to control the timbre of the sound and how the sound changes over time.
Synthesizer in music
For the most part, thanks to synth pioneer Dr. Robert Moog, synthesizers became popular in the late 60s and early 70s. Many songs are immediately recognisable by their synthesizer sounds like The Who's Baba O' Riley, Pink Floyd's On The Run and Rushs Tom Sawyer, to name but a few. Around this time, adventurous composers began to experiment with synthesizers for sound design, such as Wendy Carlos' score for "A Clockwork Orange".
Synthesizers became a mainstay of pop music with the 80s synth-pop phenomena, as musicians such as Kraftwerk and Thomas Dolby increasingly experimented with electronic instruments. Since then, electronic music has spread into numerous sub-genres such as techno, house, trance, drum' n' bass, acid, hardstyle and countless others, with each sub-genre being largely defined by the types of synthesizer sounds. (as well as other features such as tempo, arrangement and so on). Outside of electronic music, the synthesizers remain an indispensable tool for producers in a variety of musical styles such as pop, hip hop and R&B.
Different types of synthesizers
The variety of sounds that the synthesizers can produce is only matched by the many different synthesizer designs. Subtractive synths, additive synths, frequency modulation synths and wavetable synths are just some of the most common, and all have their own characteristic sound characteristics.
Modular synthesizers allow you to mix and match different modules to create the synthesizer you want. There are many software synthesizers that aim to emulate classical synthesizers and there are also many that combine elements of different types of synthesis to create hybrid instruments.