Yamaha Corporation (ja: ヤマハ株式会社) is a company founded 1887 in Hanamatsu, Japan.
In the VGM scene, Yamaha is famous for their FM sound chips.
Incomplete list of Yamaha sound chips:
All OPN chips use 4 operators per FM channel. Most chips also have a built in YM2149 core (SSG, AY-3-8910 clone, 3 SSG channels with dual 8-bit GPIO ports). The YM2612 and its deriatives do not contain the YM2149, although the envelope generator remains.
- YM2203 - (OPN) 3 channels of FM, built in SSG (adding 3 channels and dual 8-bit GPIO ports).
- YM2608 - (OPNA) 6 channels of FM, built in SSG, sampled ROM drums, as well a single ADPCM codec.
- YM2610 - (OPNB) 4 channels of FM, built in SSG. Contains one ADPCM channel with a variable sample rate, and six ADPCM channels with a fixed 18.5 kHz sample rate.
- YM2610B - (OPNB) Similar to YM2610, only with 6 FM channels.
- YM2612 - (OPN2) 6 channels of FM. Does not contain the SSG.
- YM3438 - (OPN2C) CMOS variant of YM2612, minor differences.
- YMF288 - (OPN3) 6 channels of FM, built in SSG. Does not contain ADPCM or GPIO ports.
Earlier OPL chips are only capable of 2 operators per channel, YMF262 and later chips can use 4 operators per channel while keeping the total amount of operators (slots). That is, a channel is lost for each channel with 4 operators enabled. The OPL chips can also sacrifice 3 melody channels for 5 rhythm channels.
YM3812 and later chips allow for different waveforms for each operator, not just sine waves.
- YM3526 - (OPL) 9 melody channels, or 6 melody and 4 rhythm channels. Only sine waves.
- YM3801 - (Y8950, MSX-Audio) YM3526 deriative, contains a 4-bit ADPCM codec (Similar to the YM2608).
- YM3812 - (OPL2) 9 melody channels, or 6 melody and 4 rhythm channels. Four available waveforms.
- YM2413 - (OPLL) YM3812 deriative, 15 instrument presets and one custom instrument.
- YMF262 - (OPL3, FA1006) 36 slots: 18 2op melody channels, or 15 2op melody channels and 5 rhythm channels. Two 2op channels can be exchanged for a 4op channel, for up to 6 4op melody channels.
- YMF278B (OPL4) FM part similar to YMF262, includes up to 24 PCM channels.
- YM2149 - (SSG) AY-3-8910 clone.
- YM3439 - (SSG) CMOS version of YM2149.
- YMZ284 - (SSGL) SSG in a smaller package.
- YMZ294 - (SSGLP) SSG in a smaller package, supports higher frequencies via a clock divider pin.
- YMZ705 - (SSGS) Includes two SSGs and 8 ADPCM channels, as well as a built in sequencer.
- YM2151 - (OPM) 8 voice, 4 operator FM chip.
- YM2164 - (OPP) similar to YM2151.
- YMF271 - (OPX) 48 slots, each group of 4 slots can enable one 4op FM channel, two 2op FM channels, one 3op FM channel and one PCM channel, or four PCM channels.
- YMZ280B - (PCMD8) 8 channel stereo PCM/ADPCM decoder.
Yamaha produced custom ASICs for other companies. Here's an incomplete list of these chips:
- YM6626 - (GA20) 4 channel PCM chip used by Irem.
- YM6630 - (5B) Famicom mapper used by Sunsoft, contains a built in YM2149 core.
- DS1001? - (VRC7, K053982) Famicom mapper used by Konami, contains a YM2413 deriative, differences being: no rhythm channels, 6 melody channels only, different instrument presets.
- YM7101 - (315-5313) Sega Mega Drive/Genesis Model 1 VDP. Contains an SN76489A PSG core.
- FC1004, FF1004 - (315-5487, 315-5570, 315-5700) Sega Mega Drive/Genesis Model 2 VDP. Contains a PSG and an improved YM3438 core.
- YMW258 (GEW8) 28 channel PCM chip. Similar to YMF278B. Used in the Sega System 32 Multi, Model 1 and early Model 2 boards.
- YMF292 (SCSP) 32 channel PCM/FM chip, built in DSP. Used in the Saturn as well as the Model 2 and Model 3 arcade boards.
- G21003/FQ1003 (AICA) 64 channels of PCM/ADPCM, built in DSP, built in ARM7 sound processor. Used in Sega Dreamcast and NAOMI.
-  Big list of various Yamaha chips used in various synthesizers/sound cards/keyboards, etc.