A synthesizer that uses digital signal processing (DSP) techniques to make sounds. The very earliest digital synthesis experiments were made with general-purpose computers, as part of academic research into sound generation. Perhaps the best way to begin to understand digital synthesis is to compare it to analog synthesizers. Modular analog synthesis uses voltage to perform its three primary functions. A voltage-controlled oscillator (VCO) produces a tone, which is shaped by a voltage-controlled filter (VCF). The amplitude of the resulting sound is processed by a voltage-controlled amplifier (VCA). (These basic building blocks can be rearranged in a variety of ways, but they still perform similar duties.) Digital synthesis replaces voltage with numeric representations of values; so at its most basic, a digital synthesizer uses a digitally controlled oscillator (DCO), filter (DCF) and amplifier (DCA).
However, the broader range of processing power available with DSP has allowed many variations of synthesis techniques to emerge that simply weren’t possible with analog technologies. Early commercial digital synthesizers used simple hard-wired digital circuitry to implement techniques such as additive synthesis and FM synthesis. Other techniques, such as wavetable synthesis, physicalmodelingsynthesis and granular, became possible with the advent of high-speed microprocessor and digital signal processing technology.
Some digital synthesizers now exist in the form of “soft synth” software that utilizes conventional computer hardware for processing. Virtual analog synthesizers, whether in hardware or software form, are in fact digital synthesizers that emulate the behavior of analog circuitry.