A synth which produces its output using digital computing and processing techniques. In a typical modern digital synth, the signal is not converted to analog form until it is ready to be output, although some early designs were digital-analog hybrids. Unlike analog synthesizers, nearly all of which employ subtractive synthesis, digital synthesizers may employ a number of different synthesis techniques, depending on the design. Digital synthesis goes back to the 1950s, when programs had to run on large mainframe computers all night to produce a few minutes' worth of output. It was not until late 1970s that real-time digital synthesis became practical; the first commercially produced digital synthesizer was the Fairlight CMI, introduced in 1979.