How do you expect your emu to recognize a reverse command ?
I don’t even think that any hardware sampler can reverse a sample in real time, at least my yammie A5000 doesn’t , and I doubt the emus and akai’s can do it .
Reverse sample commands only works with internal samples ;
You can send retrigger , velocity to your sampler but that’s about it .,.
What you should do , is make a duplicate of your sample ( inside the sampler ) and reverse it , then trigger it , then again your missing out on all the stuff that makes a tracker/renoise so great = REAL TIME SAMPLE COMMANDS