I run a bigger tube with the bungee. Then I put the mouthpiece end down through a Kifaru water bottle pocket at the rear of my pack belt. Goes in past the center material and out the bottom. Secure enough to stay put, but pulls right out to call. I'm a lefty bowhunter and run it on the left side of my belt.
Well if you do it the way my hunting partner does, you just never practice or really learn to call so that I'm the one left with the bugle tube most of the time.
I shove my in the load shelf of my stone glacier. Small end goes in first between the bag and the frame. I got the idea from a guy that would put his in the scabbard of his eberlestock