Chiptune by Wikipedia definition

A chiptune, or chip music, is music written in sound formats where all the sounds are synthesized in realtime by a computer or video game console sound chip, instead of using sample-based synthesis. The "golden age" of chiptunes was the mid 1980s to early 1990s, when such sound chips were the most common method for creating music on computers. Chiptunes are closely related to video game music, which often featured chiptunes out of necessity. The term has also been recently applied to more recent compositions that attempt to recreate the chiptune sound for purely aesthetic reasons, albeit with more complex technology.

Early computer sound chips had only simple tone and noise generators with few channels, imposing limitations on both the complexity of the sounds they could produce and the number of notes that could be played at once. In their desire to create a more complex arrangement than what the medium apparently allowed, composers developed creative approaches when developing their own electronic sounds and scores, employing a diversity of both methods of sound synthesis, such as pulse width modulation and wavetable synthesis, and compositional techniques, such as a liberal use of arpeggiation. The resultant chiptunes sometimes seem harsh or squeaky to the unaccustomed listener.

Modern computers can play a variety of chiptune formats through the use of emulators and platform-specific plugins for media players. Depending on the nature of hardware being emulated, 100% accuracy in software may not be available. The commonly used MOS Technology SID chip, for example, has a multi-mode filter including analog circuits whose characteristics are only mathematically estimated in emulation libraries.[1][dubious – discuss]

The chip scene is far from dead with "compos" being held, groups releasing music disks and with the cracktro/demo scene. New tracker tools are making chip sounds available to less techy musicians. For example, Little Sound DJ for the Nintendo Game Boy has an interface designed for use in a live environment and features MIDI synchronization. The NES platform has the Midines, a cartridge that turns the system into a full blown hardware MIDI controlled Synthesizer. On the DOS platform, Fast Tracker is one of the most famous chiptune makers because of the ability to create hand-drawn samples with the mouse.

Full description : http://en.wikipedia.org/wiki/Chiptune