A style of electronic music inspired by video game music and sounds, mostly that of the early 1980s. During this era, video games and microcomputers were just beginning to acquire the ability to synthesize music and sound effects beyond basic beeps. Several custom integrated circuits were developed which contained the guts of a very basic analog synthesizer, and interfaced it to the system's I/O bus so that software could control it and synchronize music and effects with the game video.
Because the circuits were fairly primitive, they produced a characteristic sound. Many of them consisted only of a very basic VCO capable of only a square wave output, a noise source, and a VCA. Often there was no filtering capability, so everything came out with the nasal sound of the raw square wave. The application software had to perform any desired modulation, and that frequently meant no modulation since the software often could not spare the CPU cycles to do it.
The Atari POKEY and the Commodore SID are frequently-used sources for creating chiptunes. Since the actual ICs are long out of production and very difficult to obtain, a number of emulators have been developed, most in the form of soft synths.