MID2CMF converts type-0 MIDI files into Creative Music Format (.cmf) files. CMF files use MIDI data internally, but like MOD files they contain custom instruments (in this case OPL instruments as opposed to MOD's sampled instruments.)
This converter is quick and dirty - it copies the MIDI data pretty much as is, only remapping the GM instrument numbers to CMF equivalents starting at zero. Sysex data is left intact, and while this complies with the CMF "standard" (i.e. Creative's official player handles it) other players have some difficulty. This can be avoided by clearing all sysex data before exporting.
The converter also only accepts a type-0 MIDI file, as these keep the MIDI data in a single track as CMF files do.
A default set of patches are used which sound a bit like GM instruments, but it is expected that anyone performing a conversion will use a program like SBTimbre (DOS) to set patches after conversion - the default patches are only to serve as a guide.
Percussion is not yet converted. Percussion instruments should be placed on separate channels in the MIDI file for them to be converted properly. The channel is unimportant (i.e. they don't need to be on channel 10.) To be fully OPL2 compliant, the maximum polyphony is nine notes. (Rhythm mode would allow six notes and five percussion polyphony, but this is not implemented.)