After quite a few years of elk hunting, my experience is that cows will not come in to a call, and will actually push them out of the area. Maybe there are other people who have had luck calling them in, but I have not. I just keep quite and put myself in a spot where I knows cows are going to cross and focus on staying downwind. A call can be useful to just get a cow to stop and look at you, but once that brief pause is over, they're going to move in a different direction.
I also drew a 1st season rifle cow tag. At least where I hunt, the elk are still going to be in the rut. So I will call only to locate the herd. Once I get close (with a cow tag) I just keep quite.
Time after time, whether with a bugle or a cow call, I've called in bulls, and watched the cows with their ears back in caution with no interest in getting closer to the call. Again, this is just my experience.