"My main pastime for many years was change-ringing; the ringing of bells in mathematical patterns rather than randomly or in tunes. Often heard as a disorganized jangle as ringers learn the basic stages, in its advanced forms it is a complex changing pattern of sound in a perfectly smooth rhythm.
As a human achievement, it is one of the most complex, requiring the memorizing of the patterns (called ``methods''), the watching of the other ropes (``ropesight'' -- you do not, on the whole, know in advance which bell yours will be after), and the manual timing of an instrument which sounds around two seconds after you pull the rope, to an accuracy, when done well, of around 20 milliseconds.
Each bell weighs typically between a tenth of a ton and a ton, although there are bells weighing only a hundredweight and there are some weighing several tons. The bell is mounted on a headstock, a beam which is attached to the wheel, a spoked wooden wheel several feet across. The rope is attached to the rim of the wheel, and can wind round it in either direction. Starting from the bell being at rest at one end of its travel, when it is mouth-upward and just beyond the balance, when you pull the rope, the bell goes over the balance, swings through the mouth-down position, and back up to mouth-up just over the balance in the other direction. As the bell comes to a rest, the clapper catches up with it, and the bell sounds. You can vary the timing by how hard you pull; a gentle pull means the bell will not quite reach the balance, and so will stop, and return for the next stroke, sooner; a harder pull sends it further over the balance, giving a slower stroke.
Being heavy, the bell has a natural rhythm, like a pendulum: different amounts of pull have only a small effect on the timing. Ringing is arranged into rows; in each row, all the bells sound once each. The timing changes described above allow a bell to move one place in the row between rows; it can swap with the one before it, or the one after it, or stay where it is. The sequences of these changes are called methods, and these are what the ..."