We seldom use a bugle tube, and we often cow call, well not so conservatively, and we get action. The buddy system works well for us, shooter between caller and elk, and go from there. We've also called "blind" and called in satelite bulls that never bugled.
We use open reed calls and diaphram, even a hoochie momma on rare occasions. As Huntingson mentioned, we use several cow calls on any one stand to create the sounds of several different cows, and that really seems to work for us.