I'll assume that this question is referring to the mapping of specific keys (notes) to specific percussion instruments (drums etc) for the purposes of midi transmission.

If a specific music device is claimed as GM compatible then yes, it should follow the GM mapping for percussion. If a device is NOT claimed as GM compatible, then it could do whatever. The GM mapping is fairly arbitrary, as far as I can tell, I'm not sure there is any more 'logic' to it that any other arrangement.

I am sure there is software that will do a conversion from specific map A to specific map B, although I'd guess that there will always be possible problems because device A and device B will not necessarily call the same percussion instrument the same thing. When I wrote some software to convert Yamaha ESEQ files to GM I had some problems with this, although most 'drums' seems to match OK. I think I had some problems between Roland MT-32 midi files and GM as well.

I suspect that such a program would need a 'map file' that could be created anew for each pair of devices (convert from, and to) as required, as it may be not practical to have one program convert with all possibilities. There is also the problem as to which data in any midi file is percussion, to be converted, and which is normal music NOT to be converted. Having percussion on Ch 10 may be fairly reliable, but not 100%, but any program could require this part of the process to be entered (or set in any 'map file'?

Always going to be difficult to get any conversion EXACTLY so?

Geoff