I am a ringer as well as a musician. The aim of ringing composers is to include as much 'music' as possible when designing ringing methods and peal compositions. Some changes are regarded as being more musical than others, particularly if they contain 'runs' of bells such as 8765 or 5678, these are called 'roll-ups'. Other specific changes out of the thousands of available permutations which are regarded as particularly musical are 'Queens' (13572468), 'Whittingtons' (12753468) and 'Titums' (15263748) which have a certain symmetry to them. Each change (permutation) may only appear once in a piece of ringing, so composers (who have a tendancy to be mathematicians) employ complex maths to maximise the music, and see a mathematical beauty in the unfolding of the changes as they are rung. So yes, I think it is music and a ring of bells is a musical instrument. It is very hard to master though, and you can't practice in your front room, so unfortunately the public can be subjected to a lot of lousy ringing as people try to improve. A peal of bells rung really well is a joy to listen to.