Bell muffles - for when you only kinda want to make a bell quieter

Ringing "half-muffled" is something mentioned on this channel before and over on the ‪@St_Matts_Bells‬ channel periodically. But what does that actually mean? What does it involve? Why is it done?
In my own 16 years of ringing, I'm aware of us ringing half-muffled only 3 times during that period. I figured that other people would know even less than me, so I've put together some answers for (hopefully) all of your questions!
Thanks to everyone at St Matthew's Society of Bellringers for their support.
Video production by Scott Pilkington @spil030 2022