A digital synthesizer is a synthesizer that uses digital signal processing (DSP) techniques to make musical sounds. Electronic keyboards make music through sound waves. The very earliest digital synthesis experiments were made with general-purpose computers, as part of academic research into sound generation. Early commercial digital synthesizers used simple hard-wired digital circuitry to implement techniques such as additive synthesis and FM synthesis, becoming commercially available in the early 1980s. Other techniques, such as wavetable synthesis and physical modeling, only became possible with the advent of high-speed microprocessor and digital signal processing technology. One of the earliest commercial digital synthesizers was the Synclavier.
The Yamaha DX7 was the first commercially successful all-digital synthesizer. It became indispensable to many music artists of the 1980s.
Some digital synthesizers now exist in the form of "softsynth" software that synthesizes sound using conventional PC hardware, though they require careful programming and a fast CPU to get the same latency response as their dedicated equivalents. In order to reduce latency, some professional sound card manufacturers have developed specialized digital signal processing hardware. Dedicated digital synthesizers frequently have the advantage of onboard accessibility, with switchable front panel controls to peruse their functions, whereas software synthesizers trump their dedicated counterparts with their additional functionality, against the handicap of a mouse-driven control system.
With focus on performance-oriented keyboards and digital computer technology, manufacturers of commercial electronic instruments created some of the earliest digital synthesizers for studio and experimental use with computers being able to handle built-in sound synthesis algorithms.
Analog vs. digital
The main difference is that a digital synthesizer uses digital processors and analog synthesizers use analog circuitry. A digital synthesizer is basically a computer with software used as an interface. An analog synthesizer is made up of sound-generating circuitry and modulators. Another difference is the price. Digital synthesizers can be run with a MIDI control, thus equipment is much cheaper depending on what quality of sound one is looking for. Also the price of the computer, its CPU speed, and software interface also determine the money spent. Analog synthesizers contain their own controls on the circuit board, making them harder to learn but more capable of creating its own unique sound instead of using a preset from software. 
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