Dog howling at harmonica?

So I practice the harmonica frequently and have 2 dogs at home. One is a terrier mix and the other is pure bred dashound(though he's the runt of the litter and quite the wiseass). Now when I play around them the terrier has absolutely no problem with the sounds high or low of the harmonica but when I hit the lower bends the wiseass whines and howls at me. I was wondering does this have to do with him having stronger ears and it hurting him. Or is it just his nature as a hound dog to howl at the blues?