In libsound/sound-view.c:

static gchar* generate_event_label(SoundEvent *event)
{
	//For now I just make the mnemonic char the first char in string. Do we want to
	//come up with an explicit mapping
	return g_strdup_printf("_%s:", event->desc);
}

It won't work when the first character does not match with a key.  Many non-latin languages require several keystrokes or even a popup to enter a character.

I propose just not to use any mnemonic -- IMHO adding mnemonic here is not much useful.