Fran, if you use something like GNMidi and you can figure out the difference between Yamaha and the Roland Drumkits you could then develop a translation table (note number transfers) and change all the midi files and save them with this new translation. Yes, unfortunately you end up with 2 separate sets of midi files - not good - but it works. You can save this translation table in GNMidi. It is still a big boring job but it can be done.

The easist is to use a laptop and have two software synths installed which use both systems, e.g., LiveSynth Pro/sYnerGiGS for Yamaha styles and midis and Edirol HQ Sound Canvas for Standard Midi or Roland Midis. You would also need a DXi Wrapper, Brainspawn, Project5, etc. Regular midis (Roland) sound fairly good on the LiveSynth just not as good as on a Sound Canvas (soft or hardware). At least you don't get the handclaps and dogs howling, etc. LiveSynth/sYnerGiGS have 2 sets of Drumkits (XG-Bank 127 and GM/GS-Bank 128).

I have both of these synths and they sound very good and take about 10 - 15% resources of a 2.0 GHz Pentium 4 Processor. If you take a laptop with you on a gig this could be a very viable option to using hardware modules like the SC88, etc.

DNJ & Fran, I should have added in my previous post that sometimes the problems between Yamaha and Roland Midis comes from the fact that the Yamaha styles or midis call up drumkits from Bank 127 (16256). If you have a regular GM/GS Wavetable then who knows what you would get, gun shots, birds chirping and so on.

To fix this you have to call up the midi in question in a sequencer like Cakewalk and change to the appropriate Drumkit Bank (usually Bank 128). Another big boring job!!!

The good news is you only have to go thru this once in your life.

General midi was supposed to eliminate erronous notes, but Yamaha seems to skate that issue and use whatever notes they want in their drum sets. It's a good thing that they use very logocal drum patterns in their own keyboards, because they do not fair well in the GM department. They've gotten better, but they are still behind ROland in GM playback.
I realize that sounds are evolving at breakneck paces, but GM is suppose to be GENERAL. Ya know? Same notes...same sounds for all. I guess they think they're above all that.