This is what I’d call it, as well.
I just realized - your reputation is shown in every post.
It’s right below your post count. I’ve been here how long?:o
If you want to change the tune of the bells. You would have to cut them and tune them to your specific chord you desire then re glue them. The set screw on the back can be adjusted. 1/16th at a time no more then 1/8". You will have to take them off and reassemble on a bench or the ground. Pressure rise them and listen for what horn is not firing right away. You will hear it. Then adjust a hair then fire off until the all voice at the same time. I have in the past made different custom chord tunes on the black plastic horns that HB sells. Good Luck and dont get heavy handed when adjusting diaphragm on back cap.