Digital sound revolution

The digital sound revolution (or digital audio revolution) refers to the widespread adoption of digital audio technology in the computer industry beginning in the 1980s.

Some of the first computer music was created in 1961 by LaFarr Stuart, who wrote software to modulate the duration of and between pulses (pulse-width modulation or "PWM", via a process now often referred to as "bit banging") on a bus line that had been connected to an amplified speaker originally installed to monitor the functioning of Iowa State University's CYCLONE computer, a derivative of the Illiac. The entire computer was used to create simple, recognizable tunes using digital audio.

The speakers in the IBM PC (released in 1981) and its successors may be used to create sounds and music using a similar mechanism.

Programmable sound generators were the first specialized audio circuits in computers included simple analog oscillators that could be set to desired frequencies, generally approximating tones along the musical scale. An example of this is the 1978 POKEY custom ASIC used in the Atari 8-bit computers.

The next development was to produce a base frequency, and then modulating it with another frequency to create desired effects; this process of audio waveform synthesis using frequency modulation is usually referred to as FM synthesis. This technology was introduced in the early 1980s by Yamaha, which began manufacturing FM synth boards for Japanese computers such as the NEC PC-8801 and PC-9801 in the early 1980s. This allowed personal computer game audio to have greater complexity than the simplistic beeps from internal speakers. These FM synth boards produced a "warm and pleasant sound" that musicians such as Yuzo Koshiro and Takeshi Abo utilized to produce video game music that is still highly regarded within the chiptune community.

Early integrated circuit devices to incorporate FM synthesis methods include the Yamaha OPL2 chip set (YM3812 and external digital-to-analog converter) was included on the AdLib sound card (1987), on the Creative Technology Sound Blaster (1989), and on the Media Vision Pro AudioSpectrum (1991); these were replaced by the next generation Yamaha OPL3 chip set on the Pro AudioSpectrum 16 and Sound Blaster 16.

As they became more cost-effective, digital-to-analog converter (often called "D-to-A"—abbreviated "D/A", or "DAC") integrated circuits augmented and ultimately replaced FM synthesis devices. These devices enabled computers to play digital audio using an encoding technique known as pulse-code modulation ("PCM"). Unlike pulse-width modulation ("PWM"), which turns a signal on and off, pulse-code modulation also allows the level of a signal to be set to several intermediate levels; in this regard, PWM is similar to black-and-white images, PCM is similar to grayscale images.

Digital audio compact discs (using PCM) were introduced in 1982. Starting in 1985, the medium was adapted for the storage of computer data via the Yellow Book CD-ROM standard and the High Sierra Format (which evolved in ISO 9660).