From my observations of elk in the winter; when they are not being hunted by humans; is that they pretty much know the 'voice' of other elk in their family groups. An elk can live over 30 years; and in that time produce many generations.
Just like you might remember the voice of someone in your family - they can recognize the vocalizations of elk they congregate with.
I took my hoochie momma call; and numerous other calls and have watched the reactions of the elk that winter here. I can walk out the door in the winter and see 500 different elk; and can hear them while inside my cabin.
What I have noticed is that every call I have used has alerted elk in the winter- except one.
The hoochie momma that works in the fall when different groups of elk are gathered up in the breeding season; and are going through different hormonal phases.. might spook the heck out of elk in the winter ( and has).
All the calls mentioned above I have tried in the winter; and all upset the elk at that time.
The only call that does not upset them; and that can be used to call in elk in the fall is the OLD STYLE 'elk inc' call; a folded plastic call with a rubber band for a reed.
Why- I have no idea.
As Wahoo mentioned - the use of calls here in Idaho is becoming less and less a working method of getting elk in. It might be because of the wolf pressure that seems to have the effect of bunching elk up. ( I saw 93 elk in one herd -three days ago).
Bunched up they might stay more familiar with each others individual tone of their calls.
When I watch elk now I see that body language is used by elk more than vocal calls. For instance- I don't hear elk bark as much as I see them look physically alert. Perhaps elk here have found that being vocal brings in the wolves.
That being said - there are other ways to call in an elk.
When elk are silent; if you take a stout branch the size of an elk antler; and smack a tree with it; and then rub the branch up and down the tree (the same size tree as you see rubs on) - you can bring bulls in.
You can find a pine tree that you can push back and forth and make a 'swishing sound' like an elk does when pushing on a tree -- that- has worked many many times for me. Raking the ground with a branch and as well bushes is imitation again of elk breeding behavior noises.
They can bring bulls in when nothing else can - so using them in a place where elk are being vocal could be a good 'calling method' to use.
The use of a decoy can work too; especially in conjunction when calling elk.
Will Primos; who I am convinced is not human; but a Vulcan - one of Spocks relatives ( and I say that with great respect for Vulcans) - used to promote the person that is calling be 50 yards behind the person doing the shooting. Now he talks about not 50: but 100 to 150. I suggest listening to what he says closely - he is a master at calling in elk- and equally importantly- how to prepare for a shot opportunity on an elk.
Elk talk is best explained by Elknut. I bow three times a day in the direction of his home.
Its not just the sound of the call; its the ability to repeat the same sounds; and when to use each sound; and when not too.
One thing people do wrong when bugling is not to use enough volume. Used to be in Boise this time of year you could hear people practicing bugling outside. Outside: because thats where wives chased bugle practice too. Indoor bugling practice is best done when nobody is there to tell you to turn down the volume.
I have heard perfect calls from new elk hunters - save the fact they sound like an elk a mile away. If you bugle- do it loudly !!
Cow calls though - they can be best when barely audible. There is even a dampening device out there that fits over a hoochie momma call that works really well.
Not that I am rambling while counting down the days here....