Chiptune History
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. In their desire to create a more complex arrangement than the restrictions posed by the medium apparently allowed, composers developed creative approaches when developing their own electronic sounds. This is due to the early computer sound chips having only simple tone and noise generators imposing limitations on the complexity of the sound. The resultant chiptunes sometimes seem harsh or squeaky to the unaccustomed listener. Chiptunes are closely related to video game music. The term has also been recently applied to more recent compositions that attempt to recreate the chiptune sound, albeit with more complex technology.
Historically, the chips used were sound chips such as:
- Ricoh 2A03 on the Nintendo Entertainment System or Famicom
- the analog-digital hybrid Atari POKEY on the Atari 400/800 and arcade hardware
- the MOS Technology SID on the Commodore 64
- AY-3-8910 or 8912 on Amstrad CPC, MSX and ZX Spectrum
- the Yamaha YM2149 on the Atari ST and ZX Spectrum
- Yamaha YM2612 on Sega Mega Drive
- Yamaha YM3812 on IBM PC compatibles
- Paula on Amiga
For the MSX several sound upgrades, such as the Konami SCC, the Yamaha YM2413 (MSX-MUSIC) and Yamaha Y8950 (MSX-AUDIO, predecessor of the OPL3) and the OPL4-based Moonsound were released as well, each having its own characteristic chiptune sound.
The Game Boy and Nintendo Entertainment System do not have a separate sound chip but both instead use digital logic integrated on the main CPU.
Most of (but not all) chip sounds are synthesised by simply dividing a clock square wave to get a square wave of desired frequency, and sometimes using a sawtooth/triangle wave from volume LFO or an (ADSR) envelope to get some kind of ring modulation. LFOs are used to control or influence a sound parameter such as pitch or filters in a repeating cycle. It can be found as function of the SID chip.
The technique of chiptunes with samples synthesized at runtime continued to be popular even on machines with full sample playback capability; because the description of an instrument takes much less space than a raw sample, these formats created very small files, and because the parameters of synthesis could be varied over the course of a composition, they could contain deeper musical expression than a purely sample-based format. Also, even with purely sample-based formats, such as the MOD format, chip sounds created by looping very small samples still could take up much less space.
As newer computers stopped using dedicated synthesis chips and began to primarily use sample-based synthesis, more realistic timbres could be recreated, but often at the expense of file size (as with MODs) and potentially without the personality imbued by the limitations of the older sound chips.
The standard MIDI file format, together with the General MIDI instrument set, describes only what notes are played on what instruments. General MIDI is not considered chiptune as a MIDI file contains no information describing the synthesis of the instruments.
Common file formats used to compose and play chiptunes are the SID, SNDH, MOD, XM, several Adlib based file formats and numerous exotic Amiga file formats.