People actually use chainsaws to call moose in areas where there is currently logging, and you will hear the loggers talk about it. over time the moose realize that when they hear chainsaws there are very soon fresh young branches from the tops of trees (preferred food in late fall-winter) laying on the ground. the moose also realize that loggers don't care about them and so they come running in to the sound of chiansaws like a dinnerbell. I've heard of people going out to fresh cuts revving a chainsaw and within minutes had moose running straight for them looking for a snack. I guess you could say stihl entered the moose call market.
Natural voice is the way to go 100%! if you're looking to kill moose without knowing how to make a grunt or moan you'll have a much harder time with it. moose make lots of noise when moving through the bush so if you give a few calls while moving you can easily still hunt or stalk right up to one (provided good wind).