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.