GYM is a sound format (similar to NSF) for the Sega Genesis/Mega Drive.

The name stands for Genesis YM2612, since the file contains the data sent to the Yamaha YM2612 sound chip in the console. The data is ripped (logged to a file) through the use of emulators running a ROM image.

The GYM format first appeared on the emulator Genecyst as a simple raw sound data log. This means the format does not present a proper heading or any kind of sample storage, what usually creates very large files for a complete song.

Also, the GYM format has a time accuracy of 16 ms (1/60th of a second), what makes it improper for logging audio in any frequency other than 60 Hz (such as the 50 Hz found in European systems). Some new emulators and players had implemented headers, frequency compatibility and even some compression, but they do not follow any standard, which decreases the compatibility of the format.

GYM files can be played using Winamp (with the proper plugins) or with special players.

The new file format VGM also supports Yamaha YM2612 logging and is already supported by many popular emulators. It includes a complete header with tagging and looping support, what renders GYM files obsolete for this kind of music storaging. Still, GYM is much more popular and there are few VGM soundtracks (of this system) avaiable at this date.

Specifications

The GYM file format contains only four different instructions, each represented by one byte:

0x00      wait 1/60th of a second
0x01 R D  write data D on YM port 0, register R
0x02 R D  write data D on YM port 1, register R
0x03 D    write on PSG port the data D

External links

• Zophar.net GYM page, with GYM packs and plugins for download

GYM is also the third CD by the Norwegian pop/rock band Di Derre.