To change the name but not the sound file....
Menu/System /Engine set up/ Edit engine/Edit Name/ select the engine and a list of letters comes up on screen,
Name the engine to whatever you want and hit the "D: for done.
if the engine is factory reset you'll have to re-add the engine and do the name thing over again.
Last time I checked, a feature reset saves the engine's ID but the name is now also lost, After 15 years of retaining the name MTH has screwed it up.... I don't know if version 6 fixed the problem.