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Revision as of 16:55, 25 March 2019 by M1911 (talk | contribs) (Unsupported Games)
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YM2149 Music
Developer: Arnaud Carré
Header: Custom
Content: Log
Instruments: Combined
Target Output
Output - Digital Audio - No.png Output - MIDI - No.png Output - FM Synthesis - No.png Output - PSG.png
Released: 19??-??-??
First Game: N/A
  • *.ym
  • *.ym5
Not to be confused with GYM.

YM (YM2149 Music) is an audio format that logs instructions sent to an AY-3-8910 or YM2149 chip. Playback occurs by emulating the chips and sending the logged data to them. Because the format merely logs the instructions to the chip, it doesn't preserve the original content of the music format. The format is similar to VGM, DRO and GYM formats in this respect. Although YM technically supports any platform that uses the specified chips, the logging community has mostly limited its efforts to the Amstrad CPC. The format has partial support for the YM2149F used in Atari ST.

MYM is a variation of the YM format tailored for replay on low-end platforms.





YM to ?

? to YM



Games that rely solely on an AY-3-8910 or YM2149 for music can be logged to YM format.

How to Obtain

YM files can be logged using some Amstrad CPC and ZX Spectrum emulators (see the YM Logging guide). YM archives can be found on the following pages:

Unsupported Games

Games that use audio output beyond the 3 voice chip (like the Spectrum's DAC or the PC Speaker), cannot have those portions logged to YM, and should be ripped to AY instead. This list contain Amstrad CPC games, since the format is used mostly for this platform.


All YM files are compressed LHA archives, which contain one generic file inside. It can be extracted with 7-Zip, for example (use right click on file, 7-Zip context menu, and then choose "Open archive"). The extracted file has custom header which is relatively simple, which varies on the YM version used ("YM3!" to "YM6!").

All YM files contain the words like "file.bin" or "file.ym" at the beginning (in the last case - if the file was logged using this guide), because of LHA archive format.

There are another three main differences between AY and YM format. It seems that YM supports AY-3-8912 not only for systems with Zilog 80 chip, but YM doesn't support ZX Spectrum's buzzer. But when the AY can contain a lot of tracks, YM is a single; and while AY can contain digital music (Ghostbusters (ZXS) for example), YM can't, trying to logging it will result to unproperly recorded PSG instead of PCM.

Starting from YM4 version, YM supports digital instruments. Starting from YM5 version, YM supports special sync effects. YM6 supports one more effect.

The AY-3-8910 generates frequencies on the basis on its own master frequency. Since YM logs the AY-3-8910 native commands and the master frequency changes from one computer to another (ex. ZX Spectrum: 1Mhz, Atari ST: 2Mhz), all YM commands related to periods or frequencies must be adapted in order to play correctly on a non-native platform.