Chiptune - Technology

Technology

Historically, the chips used were sound chips such as:

• the MOS Technology SID on the Commodore 64
• the analog-digital hybrid Atari POKEY on the Atari 400/800 and arcade hardware
• Ricoh 2A03 on the Nintendo Entertainment System or Family Computer
• AY-3-8910, or 8912 on Amstrad CPC, Sinclair ZX Spectrum 128 and Atari ST(Yamaha YM2149), Atari Falcon (Yamaha Y3439-F), MSX
• SN76489 on Sega Master System and Sega Game Gear.
• Yamaha YM2608 on NEC's PC-88 and PC-98
• Yamaha YM2612 on Genesis/Mega Drive
• Yamaha YM3812 on IBM PC compatibles

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, like the NES, does not have a separate sound chip but both instead use digital logic integrated on the main CPU.

On the ZX Spectrum 128k models, Amstrad CPC, and Atari ST, chip sounds are synthesised by simply dividing a clock square wave to get a square wave of desired frequency, and then using a sawtooth/triangle wave from volume LFO or an (ADSR) envelope to get some kind of ring modulation. The actual sound generation on the Sinclair ZX Spectrum/Timex series and later badged Amstrad non-CPC version evolved from a variation of the combined oscillator system that made up the tone generation system for the tape/cassette output on the original ZX80/81 series; even in the Spectrum, this slaved oscillator was used to provide the output tones for the tape/cassette output, in contrast to the discrete sound chip based system system used by the Amstrad CPC and Atari ST and a discrete tone generation circuit used for tape/cassette output on the Amstrad CPC series.

The technique of chiptunes with samples synthesized at run time 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 limits of the older sound chips.

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, SAP, YM, VGM, SNDH, MOD, XM, several Adlib based file formats and numerous exotic Amiga file formats.