My wife is a bell ringer and although I have never indulged, I have taken the time to understand it a little more.

Yes, it is mathematical. It is correctly called change ringing or ringing the changes, as bells swap places as you ring from high to low, in a methodical manner, (the different "tunes" are called methods.)

There is an excellent website

Learning to ring

Now, is it music? As music is an abstract idea in the first place, its a debate I for one wouldn't want to go down!