a mute terrier is diffrent to a hard dog.
infcat most hard dogs arent mute, the just dont bay but will be at their quarry.
a truely mute terrier is one that stands off its quarry like a baying dog but dosent bay, ive seen it a few times, they are still and staring. some people keep them and have sucess with them, i personally think its a line trait fault and should be culled out. some young dogs do it but this is all part of the learning process.